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quad channel, 16-bit, serial input, 4 ma to 20 ma and voltage output dac, dynamic power control, hart connectivity data sheet AD5755-1 rev. e document feedback information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 ?2011C2012 analog devices, inc. all rights reserved. technical support www.analog.com features 16-bit resolution and monotonicity dynamic power control for thermal management current and voltage output pins connectable to a single terminal current output ranges: 0 ma to 20 ma, 4 ma to 20 ma, or 0 ma to 24 ma 0.05% total unadjusted error (tue) maximum voltage output ranges (with 20% overrange): 0 v to 5 v, 0 v to 10 v, 5 v, and 10 v 0.04% total unadjusted error (tue) maximum user programmable offset and gain on-chip diagnostics on-chip reference (10 ppm/c maximum) ?40c to +105c temperature range applications process control actuator control plcs hart network connectivity general description the AD5755-1 is a quad, voltage and current output dac that operates with a power supply ra nge from ?26.4 v to +33 v. on- chip dynamic power control minimizes package power dissipation in current mode. this is achieved by regulating the voltage on the output driver from 7.4 v to 29.5 v using a dc-to-dc boost converter optimized for minimum on-chip power dissipation. each channel has a corresponding chart pin so that hart signals can be coupled onto the current output of the AD5755-1. the part uses a versatile 3-wire serial interface that operates at clock rates of up to 30 mhz and is compatible with standard spi, qspi?, microwire?, dsp, and microcontroller interface standards. the interface also features optional crc-8 packet error checking, as well as a watchdog timer that monitors activity on the interface. product highlights 1. dynamic power control for thermal management. 2. 16-bit performance. 3. multichannel. 4. hart compliant. companion products product family: ad5755 , ad5757 hart modem: ad5700 , ad5700-1 external references: adr445 , adr02 digital isolators: adum1410 , adum1411 power: adp2302 , adp2303 additional companion products on the AD5755-1 product page functional block diagram AD5755-1 09226-101 av ss ?15v/0v agnd av dd +15v a v cc 5.0v dv dd dgnd ldac clear sclk sdin sync sdo fault dc-to-dc converter digital interface reference current and voltage output range scaling alert refout refin notes 1. x = a, b, c, and d. ad1 ad0 dac a sw x v boost_x gain reg a offset reg a r set_x chartx +v sense_x v out _x i out_x dac channel b dac channel a dac channel c dac channel d 7.4v to 29.5v + figure 1.
AD5755-1 data sheet rev. e | page 2 of 52 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 general description ......................................................................... 1 product highlights ........................................................................... 1 companion products ....................................................................... 1 functional block diagram .............................................................. 1 revision history ............................................................................... 3 detailed functiona l block diagram .............................................. 4 specifications ..................................................................................... 5 ac performance characteristics ................................................ 8 timing characteristics ................................................................ 9 absolute maximum ratings .......................................................... 12 esd caution ................................................................................ 12 pin configuration and function descriptions ........................... 13 typical performance characteristics ........................................... 16 voltage outputs .......................................................................... 16 current outputs ......................................................................... 20 dc - to - dc block ......................................................................... 24 reference ..................................................................................... 25 general ......................................................................................... 26 terminology .................................................................................... 27 theory of operation ...................................................................... 29 dac architecture ....................................................................... 29 power - on state of the ad5755 -1 ............................................. 29 serial interface ............................................................................ 30 transfer function ....................................................................... 30 registers ........................................................................................... 31 programming sequence to write/enable the output correctly ...................................................................................... 32 changing and reprogramming the range ............................. 32 data registers ............................................................................. 33 control r egisters ........................................................................ 35 readback operation ................................................................... 38 device features ............................................................................... 40 output faul t ................................................................................ 40 voltage output short - circuit protection ................................ 40 digital offset and gain control ............................................... 40 status readback during a write .............................................. 40 asynchronous clear ................................................................... 41 packet error checking ............................................................... 41 watchdog timer ......................................................................... 41 output alert ................................................................................ 41 internal reference ...................................................................... 41 external current setting resistor ............................................ 41 hart ........................................................................................... 42 digital slew rate control .......................................................... 42 power dissipation control ......................................................... 43 dc - to - dc converters ............................................................... 43 ai cc supply requirements static .......................................... 44 ai cc supply requirements slewing ...................................... 44 applications information .............................................................. 46 vol tage and current output ranges on the same terminal ...................................................................................... 46 current output mode with internal r set ................................ 46 precision voltage reference se lection ..................................... 46 driving inductive loads ............................................................ 47 transient voltage protection .................................................... 47 microprocessor interfacing ....................................................... 47 layout guidelines ....................................................................... 47 galvanically isolated interface ................................................. 48 industrial hart capable analog output application shared v out_x and i out_x pin ...................................................... 49 outline dimensions ....................................................................... 50 ordering guide .......................................................................... 50
data sheet AD5755-1 rev. e | page 3 of 52 revision history 11/ 12 rev. d to rev. e changes to figure 2 ........................................................................... 4 changed thermal impedance from 20 c/w to 28c/w .......... 12 changes to pin 6 description ........................................................ 13 changes to pin 27 description ...................................................... 14 changes to figure 26 ...................................................................... 19 changes to dut_ad1, dut_ad0 description, table 9 ......... 33 changes to packet error checking section and internal reference section ............................................................................ 41 changes to figure 81 ...................................................................... 43 changes to figure 86 ...................................................................... 47 changes to figure 89 ...................................................................... 49 7 /12 rev. c to rev. d changes to figure 89 ...................................................................... 49 updated outline dimensions ........................................................ 50 5 /12 rev. b to rev. c changes to companion products section ..................................... 1 changes to figure 2 ........................................................................... 3 changes to table 5 .......................................................................... 15 changes to figure 22 ...................................................................... 18 added i ndustrial hart c apable a nalog o utput a pplication s hared v out _x and i out _x p in section and figure 89, renumbered sequentially .............................................................. 49 updated outline dimensions ........................................................ 50 11/11 rev. a to rev. b removed voltage output test conditions/comments , table 1 .... 5 changed headroom and footroom test conditions/ comments, table 1 .............................................................................................................. 5 changes to figure 4 ........................................................................ 10 changes to figure 5 ........................................................................ 11 changes to sclk description, table 5 ........................................ 13 changes to figure 12 ...................................................................... 16 changes to figure 21 ...................................................................... 18 changes to figure 37 ...................................................................... 20 changes to figure 44 ...................................................................... 22 changes to figure 71 ...................................................................... 29 changes to power - on state of the ad5755 - 1 section ............... 30 changes to table 17 ................................ ........................................ 35 changes to readback operation section and table 26 .............. 38 changes to voltage output short - circuit protection section .. 40 changes to figure 78 ...................................................................... 41 changes to figure 82 ...................................................................... 44 changes to figure 83, figure 84, and figure 85 .................................. 45 changes to transient voltage protection section and figure 86 ... 47 changes to galvanically isolated interface section .................... 48 5/11 rev. 0 to rev. a removed endnote 6 (table 1) ......................................................... 6 c hange d av dd minimum value from 10.8 v to 9 v ................... 6 changed ai ss minimum value from ?1.4 ma to ?1.7 ma ......... 7 c hange d av dd voltage in pin 19 description ............................ 13 changes to ordering guide ........................................................... 48 4 /11 revision 0: initial version
AD5755-1 data sheet rev. e | page 4 of 52 detailed functional block diagram AD5755-1 09226-001 av ss ?15v/0v agnd av dd +15v a v cc 5.0v dv dd dgnd ldac clear sclk sdin sync sdo fault dc-to-dc converter power control input shift register and control status register power-on reset reference buffers dac reg a input reg a vref watchdog timer (spi activity) vout range scaling alert refout refin ad1 ad0 dac a 16 16 sw a v boost_a gain reg a offset reg a r1 r2 r3 r set_a charta +v sense_ a v out_a i out_b , i out_c , i out_d r set_b , r set_c , r set_d chartb, chartc, chartd +v sense_b , +v sense_ c , +v sense_ d v out_b , v out_c , v out_d i out_a dac channe l b dac channe l a dac channe l c dac channe l d sw b , sw c , sw d v boost_b ,v boost_c ,v boost_d 7.4v to 29.5v reg v sen1 v sen2 30k? figure 2.
data sheet AD5755-1 rev. e | page 5 of 52 specifications av dd = v boost _x = 15 v; av ss = ? 15 v /0 v; dv dd = 2.7 v to 5.5 v; av cc = 4.5 v to 5.5 v ; dc - to - dc converte r disabled; agnd = dgnd = gndsw x = 0 v ; refin = 5 v; v oltage o utputs : r l = 1 k?, c l = 220 pf ; current o utputs : r l = 300 ?; all specifications t min to t max , unless otherwise noted. table 1 . parameter 1 min typ max unit test condition s/comments voltage output output voltage ranges 0 5 v 0 10 v ?5 +5 v ? 10 +10 v 0 6 v 0 12 v ?6 +6 v ? 12 +12 v accuracy bipolar supply av ss = ?15 v, loaded and unloaded resolution 16 bits total unadjusted erro r (tue) ?0.04 + 0.04 % fsr ?0.0 3 0.0032 +0.0 3 % fsr t a = 25c tue long - term stability 35 ppm fsr drift after 1000 hours, t j = 150c relative accuracy (inl) ?0.006 0.0012 +0.006 % fsr 0 v to 5 v, 0 v to 10 v, 5 v, 10 v ranges ?0.008 0.0012 +0 .008 % fsr on overranges differential nonlinearity (dnl) ?1 +1 lsb guaranteed monotonic zero - scale error ?0.03 0.002 +0.03 % fsr zero - scale tc 2 2 ppm fsr/c bipolar zero error ?0.03 0.002 +0.03 % fsr bipolar zero tc 2 1 ppm fsr/c offset error ?0.03 0.002 +0.03 % fsr offset tc 2 2 ppm fsr/c gain error ?0.03 0.004 +0.03 % fsr gain tc 2 3 ppm fsr/c full - scale error ?0.03 0.002 +0.03 % f sr full - scale tc 2 2 ppm fsr/c accuracy unipolar supply 2 av ss = 0 v total unadjusted error (tue) ?0.06 0.025 +0.06 % fsr relative accuracy (inl) 3 ?0.009 +0.009 % fsr differentia l nonlinearity (dnl) ?1 +1 lsb guaranteed monotonic zero - scale error +0.22 % fsr offset error ?0.07 0.025 +0.07 % fsr gain error ?0.07 0.015 +0.07 % fsr full - scale error ?0.06 0.015 +0.06 % fsr output characteristics 2 headroom 1 2.2 v with respect to v boost supply footroom 0.7 1.4 v with respect to the av ss supply , b ip olar output r anges output voltage drift vs. time 20 ppm fsr drift after 10 00 hours, ? scale output, t j = 150c , av ss = ? 15 v short- ci rcuit current 12/6 16/8 ma programmable by user, defaults to 16 ma typical level load 1 k? for specified performance capacitive load stability 10 nf 2 f external compensation capacitor of 220 pf connected dc output impedance 0.06 ? dc psr r 50 v/v dc crosstalk 24 v
AD5755-1 data sheet rev. e | page 6 of 52 parameter 1 min typ max unit test condition s/comments current output output current ranges 0 24 ma 0 20 ma 4 20 ma resolution 16 bits accuracy (external r set ) assumes ideal resistor , see the external current setting resist or section for more information total unadjusted error (tue) ?0.05 0.009 +0.05 % fsr tue long - term stability 100 ppm fsr drift after 1000 hours, t j = 150c relative accuracy (inl) ?0.006 +0.006 % fsr differential nonlinearity (dnl) ?1 +1 lsb guaranteed monotonic offset error ?0.05 0.005 +0.05 % fsr of fset error drift 2 4 ppm fsr/c gain error ?0.05 0.004 +0.05 % fsr gain tc 2 3 ppm fsr/c full - scale error ?0.05 0.008 +0.05 % fsr full - scale tc 2 5 p pm fsr/c dc crosstalk 0.0005 % fsr external r set accuracy (internal r set ) total unadjusted error (tue) 4 , 5 ?0.14 +0.14 % fsr ?0.11 0.009 +0.11 % fsr t a = 25c tue long - term stability 180 ppm fsr drift after 1000 hours, t j = 150c relat ive accuracy (inl) ?0.006 +0.006 % fsr relative accuracy (inl) ?0.004 +0.004 % fsr t a = 25c differential nonlinearity (dnl) ?1 +1 lsb guaranteed monotonic offset error 4 , 5 ?0.05 +0.05 % fsr ?0.04 0.007 +0.04 % fsr t a = 25c offset error drift 2 6 ppm fsr/c gain error ?0.12 +0.12 % fsr ?0.06 0.002 +0.06 % fsr t a = 25c gain tc 2 9 ppm fsr/c full - scale error 4 , 5 ?0.14 +0.14 % fsr ?0.1 0.007 +0.1 % fsr t a = 25c full - scale tc 2 14 ppm fsr/c dc crosstalk 5 ?0.011 % fsr internal r set output characteristics 2 current loop compliance voltage v boost_x ? 2.4 v boost_x ? 2.7 v output current drift vs. time drift after 1000 hours, ? scale output, t j = 150c 90 ppm fsr external r set 140 ppm f sr internal r set resistive load 1000 ? the dc - to - dc converter has been characterized with a maximum load of 1 k ?, chosen such that compli - ance is not exceeded; see figure 53 and dc - dc maxv bits in tabl e 25 output impedance 100 m? dc psrr 0.02 1 a/v
data sheet AD5755-1 rev. e | page 7 of 52 parameter 1 min typ max unit test condition s/comments reference input/output reference input 2 reference input voltage 4.95 5 5.05 v for specified performance dc input impedance 45 150 m? reference ou tput output voltage 4.995 5 5.005 v t a = 25c reference tc 2 ?10 5 +10 ppm/c output noise (0.1 hz to 10 hz) 2 7 v p - p noise spectral density 2 100 nv/hz at 10 khz output voltage drift vs. time 2 180 ppm drift after 1000 hours, t j = 150c capacitive load 2 1000 nf load current 9 ma see figure 64 short-c ircuit current 10 ma line regulation 2 3 ppm/v see figure 65 load regulation 2 95 ppm/ma see figure 64 thermal hysteresis 2 160 ppm first temperature cycle 5 ppm second temperature cycle dc - to - dc switch switch on resistance 0.425 ? switch leakage current 10 na peak current limit 0.8 a oscillator oscillator frequency 11.5 13 14.5 mhz this oscillator is divided down to give the dc - to - dc converter switching frequency maximum duty cycle 89.6 % at 410 khz dc - to - dc swi tching frequency digital inputs 2 jedec compliant v ih , input high voltage 2 v v il , input low voltage 0.8 v input current ?1 +1 a per pin pin capacitance 2.6 pf per pin digital outputs 2 sdo, alert v ol , output low voltage 0.4 v sinking 200 a v oh , output high voltage dvdd ? 0.5 v sourcing 200 a high impedance leakage current ?1 +1 a high impedance output capacitance 2.5 pf fault v ol , output low voltage 0.4 v 10 k? pull - up resistor to dv dd v ol , output low voltage 0.6 v at 2.5 ma v oh , output high voltage 3.6 v 10 k ? pull - up resistor to dv dd power requirements av dd 9 33 v av ss ?26.4 ?10.8/0 v dv dd 2.7 5.5 v av cc 4.5 5.5 v
AD5755-1 data sheet rev. e | page 8 of 52 parameter 1 min typ max unit test condition s/comments ai dd 8.6 10.5 ma voltage output mode on all channels, output unloaded, over supplies 7 7.5 ma curr ent output mode on all channels ai ss ?11 ?8.8 ma voltage output mode on all channels, output unloaded, over supplies ?1.7 ma c urrent output mode on all channels di cc 9.2 11 ma v ih = dv dd , v il = dgnd , internal oscillator running, over supplies ai cc 1 ma output unloaded, over supplies i boost 2.7 ma per channel, voltage output mode, output unloaded, over supplies i boost 6 1 ma per channel, current output mode, 0 ma output power dissipation 173 mw av dd = + 15 v, av ss = ? 15 v, dc - to - dc converter enable, current output mode, outputs disabled 1 temperature range: ?40c to +105c; typical at +25c. 2 guaranteed by design and characterization; not production tested. 3 for voltage output ranges in unipolar supply mode, the inl and tue are measured beginning from code 4096. 4 for current outputs with internal r set , th e offset, full - scale, and tue measurements exclude dc crosstalk. the measurements are made with all four channels enabled loaded with the same code. 5 see the current output mode with internal r set section for more explanation of the dc crosstalk. 6 efficiency plots in figure 55, figure 56, figure 57 , and figure 58 include the i boost quiescent current ac performance chara cteristics av dd = v boost _x = 15 v; av ss = ? 15 v; dv dd = 2.7 v to 5.5 v; av cc = 4.5 v to 5.5 v ; dc - to - dc converter disabled; agnd = dgnd = gndsw x = 0 v ; refin = 5 v; v oltage outputs : r l = 2 k?, c l = 220 pf ; current o utputs: r l = 300 ?; all specifications t min to t max , unless otherwise noted. table 2 . parameter 1 min typ max unit test conditions/comments dynamic performance voltage out put output voltage settling time 11 s 5 v step to 0.03% fsr, 0 v to 5 v range 18 s 10 v step to 0.03% fsr, 0 v to 10 v range 13 s 100 mv step to 1 lsb (16 - bit lsb), 0 v to 10 v range slew rate 1.9 v/s 0 v to 10 v range power - on glitch energy 150 nv - sec digital - to - analog glitch energy 6 nv - sec glitch impulse peak amplitude 25 mv digital feedthrough 1 nv - sec dac to dac crosstalk 2 nv - sec 0 v to 10 v range output noise (0.1 hz to 10 hz bandwidth) 0.15 lsb p -p 16- bit lsb, 0 v to 10 v range output noise spectral density 150 nv/hz measured at 10 khz, midscale output, 0 v to 10 v range ac psrr 83 db 200 mv 50 hz/60 hz sine wave superimposed on power supply voltage current output output current settlin g time 15 s to 0.1% fsr (0 ma to 24 ma) see test conditions/ c omment s ms see figure 49 , figure 50 , and figure 51 output noise (0.1 hz to 10 hz bandwidth) 0.15 lsb p -p 16- bit lsb, 0 ma to 24 ma range output noise spectral density 0.5 na/hz measured at 10 khz, midscale output, 0 ma to 24 ma range 1 guaranteed by design and characterization; not production tested.
data sheet AD5755-1 rev. e | page 9 of 52 timing characteristi cs av dd = v boost _x = 15 v; av ss = ? 15 v; dv dd = 2.7 v to 5.5 v; av cc = 4.5 v to 5.5 v ; dc - to - dc converter disabled; agnd = dgnd = gndsw x = 0 v ; refin = 5 v; voltage o utpu ts : r l = 1 k?, c l = 220 pf ; c urrent o utputs : r l = 300 ?; all specifications t min to t max , unless otherwise noted. table 3 . parameter 1 , 2 , 3 limit at t min , t max unit description t 1 33 ns min sclk cycle time t 2 13 ns min sclk high time t 3 13 ns min sclk low time t 4 13 ns min sync falling edge to sclk falling edge setup time t 5 13 ns min 24 th / 32 nd sclk falling edge to sync rising edge (see figure 78 ) t 6 198 n s min sync high time t 7 5 ns min data setup time t 8 5 ns min data hold time t 9 20 s min sync rising edge to ldac falling edge (all dacs updated or any channel has digital slew rate co ntrol enabled) 5 s min sync rising edge to ldac falling edge (single dac updated) t 10 10 ns min ldac pulse width low t 11 500 ns max ldac falling edge to dac ou tput response time t 12 see the ac performance characteristics section s max dac output settling time t 13 10 ns min clear high time t 14 5 s max clear activation time t 15 40 ns max sclk rising edge to sdo valid t 16 21 s min sync rising edge to dac output response time ( ldac = 0) (all dacs updated) 5 s min sync rising edge to dac output response time ( ldac = 0) (single dac updated) t 17 500 ns min ldac falling edge to sync rising edge t 18 8 00 ns min reset pulse width t 19 4 20 s min sync high to next sync low ( d igital slew ra te control enabled) (all dacs updated) 5 s min sync high to next sync low ( d igital slew rate control disabled) (single dac updated) 1 guaranteed by design and characterization; not production tested. 2 all input signals are specified with t r = t f = 5 ns (10% to 90% of dv dd ) and timed from a voltage level of 1.2 v. 3 see f igure 3 , figure 4 , figure 5 , and figure 6 . 4 this specification applies if ldac is held low during the write cycle; otherwise, see t 9 .
AD5755-1 data sheet rev. e | page 10 of 52 timing diagrams 0 9226-002 msb sclk sync sdin ldac ldac = 0 clear 12 24 lsb t 1 v out_x v out_x v out_x t 4 t 6 t 3 t 2 t 5 t 8 t 7 t 10 t 9 t 10 t 11 t 12 t 12 t 16 t 17 t 13 reset t 18 t 14 t 19 figure 3. serial interface timing diagram 09226-003 s yn c msb msb lsb lsb input word specifies register to be read nop condition t 6 t 15 sdin msb lsb undefined selected register data clocked out sdo sclk 24 24 1 1 figure 4. readback timing diagram
data sheet AD5755-1 rev. e | page 11 of 52 sdo disabled r/w sdin sclk sync sdo 1 2 16 lsb msb dut_ ad1 sdo_ enab dut_ ad0 x x x d15 d14 d1 d0 status status status status 09226-004 figure 5 . status readback during write 200a i ol 200a i oh v oh (min) or v ol (max) to output pin c l 50pf 09226-005 figure 6 . load circuit for sdo timing diagram
AD5755-1 data sheet rev. e | page 12 of 52 absolute maximum rat ings t a = 25c, unless otherwise noted. transient currents of up to 100 ma do not cause scr latch - up. table 4 . parameter rating av dd , v boost _x to agnd, dgnd ? 0.3 v to +33 v av ss to agnd, dgnd +0.3 v to ? 28 v av dd to av ss ?0.3 v to +60 v av cc to agnd ? 0.3 v to +7 v dv dd to dgnd ? 0.3 v to +7 v digital inputs to dgnd ? 0.3 v to dv dd + 0.3 v or +7 v (whichever is less) digital outputs to dgnd ? 0.3 v to dv dd + 0.3 v or +7 v (whichever is less) refin, refout to agnd ? 0.3 v to av dd + 0.3 v or +7 v (whiche ver is less) v ou t_ x to agnd av ss to v boost _x or 33 v if using the dc - to - dc circuitry +v sense _x to agnd av ss to v boost _x or 33 v if using the dc - to - dc circuitry i out _x to agnd av ss to v boost _x or 33 v if using the dc - to - dc circuitry sw x to agnd ?0.3 to +33 v agnd, gndsw x to dgnd ? 0.3 v to +0.3 v operating temperature range (t a ) industrial 1 ? 40c to +105c storage temperature range ? 65c to +150c junction temperature (t j max) 125c 64- lead lfcsp ja thermal impedance 2 28 c/w power dissipation (t j max ? t a )/ ja lead temperature jedec i ndustry s tandard soldering j- std - 020 1 power dissipated on chip must be derated to keep the junction temperature below 125c . 2 based on a jedec 4 - layer test board . stresses above those listed under absolute ma ximum ratings may cause permanent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to abs olute maximum rating conditions for extended periods may affect device reliability. esd caution
data sheet AD5755-1 rev. e | page 13 of 52 pin configuration and fu nction descriptions 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 poc reset av dd comp lv_a charta +v sense_a comp dcdc_a v boost_a v out_a i out_a av ss comp lv_b chartb +v sense_b v out_b comp dcdc_b 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 r set_c r set_d refout refin comp lv_d chartd +v sense_d comp dcdc_d v boost_d v out_d i out_d av ss comp lv_c chartc +v sense_c v out_c 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 r set_b r set_a refgnd refgnd ad0 ad1 sync sclk sdin sdo dv dd dgnd ldac clear alert fault comp dcdc_c i out_c v boost_c av cc sw c gndsw c gndsw d sw d av ss sw a gndsw a gndsw b sw b agnd v boost_b i out_b 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 AD5755-1 top view (not to scale) 09266-006 pin 1 indicator notes 1. the exposed pad should be connected to the potential of the av ss pin, or, alternatively, it can be left electrically unconnected. it is recommended that the pad be thermally connected to a copper plane for e nhanced thermal performance. figure 7. pin configuration table 5. pin function descriptions pin no. mnemonic description 1 r set_b an external, precision, low drift 15 k current setting resistor can be connected to this pin to improve the i out_b temperature drift performance. see the device features section. 2 r set_a an external, precision, low drift 15 k current setting resistor can be connected to this pin to improve the i out_a temperature drift performance. see the device features section. 3, 4 refgnd ground reference point for internal reference. 5 ad0 address decode for the device under test (dut) on the board. 6 ad1 address decode for the dut on the board. it is not recommended to tie both ad1 and ad0 low when using pec, see the packet error checking section. 7 sync active low input. this is the frame synchronization signal for the serial interface. while sync is low, data is transferred in on the falling edge of sclk. 8 sclk serial clock input. data is clocked into the input shift register on the falling edge of sclk. this operates at clock speeds of up to 30 mhz. 9 sdin serial data input. data must be valid on the falling edge of sclk. 10 sdo serial data output. used to clock data from the serial register in read back mode. see figure 4 and figure 5. 11 dv dd digital supply. the voltage range is from 2.7 v to 5.5 v. 12 dgnd digital ground. 13 ldac load dac, active low input. this is used to update the dac register and consequently the dac outputs. when tied permanently low, the addressed dac data re gister is updated on the rising edge of sync . if ldac is held high during the write cycle, the dac input register is updated, but the dac output update only takes place at the falling edge of ldac (see figure 3). using this mode, all analog outputs can be updated simultaneously. the ldac pin must not be left unconnected. 14 clear active high, edge sensitive input. asserting this pin sets the output current and voltage to the preprogrammed clear code bit setting. only channels enabled to be cleare d are cleared. see the device features section for more information. when clear is active, the dac output register cannot be written to.
AD5755-1 data sheet rev. e | page 14 of 52 pin no. mnemonic description 15 alert active high output. this pin is asserted when there has been no spi activity on the interface pins for a pred etermined time. see the device features section for more information. 16 fau lt active low output. this pin is asserted low when an open circuit in current mode is detected , a short circuit in voltage mode is detected , a p ec error is detected , or an over temperature is detect ed (see the device features section). open - drain o utput. 17 poc power - on c ondition . this pin determines the power - on condition and is read during power - on or , alternatively , after a device reset. if poc = 0, the device is powered up with the v oltage and current channels in t ris tate mode. if poc = 1, the device is powered up with a 30 k? pull - down resistor to ground on the voltage output channe l, and the current channel is in t ri s tate mode. 18 reset hardware reset , active low input. 19 av dd positive analog supply. the v oltage range i s from 9 v to 33 v. 20 comp lv_ a optional compensation capacitor connection for v out_a output buffer . connecting a 220 pf capacitor between this pin and the v out_a pin allows the voltage output to drive up to 2 f. note that the addition of this capacitor reduces the bandwidth of the ou tput amplifier, increasing the settling time. 21 charta hart input connection for dac channel a . 22 +v sense_a sense connection for the positive voltage output load connection for v out_a . 23 comp dcdc_a dc -to - dc compensation capacitor. connect a 10 nf cap acitor from this pin to ground. used to regulate the feedback loop of the channel a dc -to - dc converter. alternatively , if using an external compensation resistor, place a resistor in series with a capacitor to ground from this pin ( see the dc -to - dc converter compensation capacitors and the ai cc supply requirements slewing sections in the device features section for more information ). 24 v boost_a supply for channel a current outpu t stage (s ee figure 73 ). this is also the supply for the v out _x stage, which is regulated to 15 v by the dc -to - dc converter . to use the dc -to - dc feature of the device, connect as shown in figure 80 . 25 v out_a buffered analog output voltage for dac channel a. 26 i out_a current output pin for dac channel a. 27 av ss negative analog supply. voltage range i s from 0 v to ?26.4 v. 28 comp lv_b optional compensation capacitor connection for v out_b output buffer . connecting a 220 pf capacitor between this pin and the v out_b pin allows the voltage output to drive up to 2 f. note that the addition of this capacitor reduces the bandwidth of the output amplifier, increasing the settling time. 29 chartb hart input connection for dac channel b . 30 +v sense_b sense connection for the positive voltage output load connection for v out_b . 31 v out_b buffered analog output voltage for d ac channel b. 32 comp dcdc_b dc -to - dc compensation capacitor. connect a 10 nf capacitor from this pin to ground. used to regulate the feedback loop of the channel b dc -to - dc converter. alternatively , if using an external compensation resistor, place a resi stor in series with a capacitor to ground from this pin ( see the dc -to - dc converter compensation capacitors and ai cc supply requirements slewing sections in the device features s ection for more information ). 33 i out_b current output pin for dac channel b. 34 v boost_b supply for channel b current output stage (s ee figure 73 ). this is also the supply for the v out _x stage, which is regulated to 15 v by the dc -to - dc converter . to use the dc -to - dc feature of the device, connect as shown in figure 80 . 35 agnd ground reference point for analog circuitry. this must be connected to 0 v. 36 sw b switching output for channel b dc - to - dc ci rcuitry . to use the dc - to - dc feature of the device, connect as shown in figure 80 . 37 gndsw b ground connection for dc - to - dc switching circuit . this pin should always be connected to ground . 38 gndsw a ground connection for dc - to - dc switching circuit . this pin should always be connected to ground . 39 sw a switching output for channel a dc -to - dc circuitry . to use the dc -to - dc feature of the device, connect as shown in figure 80 . 40 av ss negative analog sup ply pin. the v oltage range i s from ? 10.8 v to ? 26.4 v. this pin can be connected to 0 v if using the device in uni polar supply mode. 41 sw d switching output for channel d dc - dc circuitry . to use the dc - to - dc feature of the device, connect as shown in figure 80 . 42 gndsw d ground connections for dc - to - dc switching circuit . this pin should always be connected to ground . 43 gndsw c ground connections for dc - to - dc switching circuit . this pin should always be connected to ground . 44 sw c switching output for channel c d c- to - dc circuitry . to use the dc -to - dc feature of the device, connect as shown in figure 80 . 45 av cc supply for dc - to - dc circuitry .
data sheet AD5755-1 rev. e | page 15 of 52 pin no. mnemonic description 46 v boost_c supply for channel c current output stage (s ee figure 73). this is also the supply for the v out _x stage, which is regulated to 15 v by the dc -to - dc converter . to use the dc -to - dc feature of the device, connect as shown in figure 80 . 47 i out_c current output pin for dac channel c. 48 co mp dcdc_c dc - to - dc compensation capacitor. connect a 10 nf capacitor from this pin to ground. used to regulate the feedback loop of the channel c dc -to - dc converter. alternatively , if using an external compensation resistor, place a resistor in series with a capacitor to ground from this pin ( see the dc -to - dc converter compensation capacitors and ai cc supply requirements slewing sections in the device features section for more info rmation ). 49 v out_c buffered analog output voltage for dac channel c. 50 +v sense_c sense connection for the positive voltage output load connection for v out_c . 51 chartc hart input connection for dac channel c . 52 comp lv_c optional compensation capacitor connection for v out_c output buffer . connecting a 220 pf capacitor between this pin and the v out_c pin allows the voltage output to drive up to 2 f. note that the addition of this capacitor reduces the bandwidth of the output amplifier, increasing the settling time. 53 av ss negative analog supply pin. 54 i out_d current output pin for dac channel d. 55 v out_d buffered analog output voltage for dac channel d. 56 v boost_d supply for channel d current output stage (s ee figure 73 ). this is also the supply for the v out _x stage, which is regulated to 15 v by the dc -to - dc converter . to use the dc -to - dc feature of the device, connect as shown in figure 80 . 57 comp dcdc_d dc -to - dc compensation capacitor. conn ect a 10 nf capacitor from this pin to ground. used to regulate the feedback loop of the channel d dc -to - dc converter. alternatively , if using an external compensation resistor, place a resistor in series with a cap acitor to ground from this pin ( see the dc -to - dc converter compensation capacitors and ai cc supply requirements slewing sections in the device features section for more information ). 58 +v sense_d sense connection for t he positive voltage output load connection for v out_d . 59 chartd hart input connection for dac channel d . 60 comp lv_d optional compensation capacitor connection for v out_d output buffer . connecting a 220 pf capacitor between this pin and the v out_d pin al lows the voltage output to drive up to 2 f. note that the addition of this capacitor reduces the bandwidth of the output amplifier, increasing the settling time. 61 refin external reference voltage input. 62 refout internal reference voltage output. it is recommended to place a 0.1 f capacitor between refout and refgnd. refout must be connected to refin to use the internal reference. 63 r set_d an external, precision, low drift 15 k ? cu rrent setting resistor can be connected to this pin to improve the i out_d temperature drift performance. see the d evice features section. 64 r set_c an external, precision, low drift 15 k ? cu rrent setting resistor can be connected to this pin to improve the i out_c temperature drift performance. see the d evice features section. epad exposed pad. this exposed pad should be connected to the potential of the av ss pin , or , alternatively, it can be left electrically unconnected. it is recommended that the pad be thermally connected to a copper plane for enhanced thermal performance.
AD5755-1 data sheet rev. e | page 16 of 52 typical performance characteristics voltage outputs 0.0015 0.0010 0.0005 0 ?0.0005 ?0.0010 0 10k 20k 30k 40k 50k 60k inl error (%fsr) code 09226-023 10v range 5v range +10v range +5v range +10v range with dcdc av dd = +15v av ss = ?15v t a = 25c figure 8 . integral nonlinearity error vs. dac code ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 0 10k 20k 30k 40k 50k 60k dn l error (lsb) code 10v range 5v range +10v range +5v range +10v range with dcdc av dd = +15v av ss = ?15v t a = 25c 09226-024 figure 9 . differential nonlinearity error vs. dac code 10k 20k 30k 40k 50k 60k ?0.010 ?0.008 ?0.006 ?0.004 ?0.002 0 0.002 0.004 0.006 0 total unadjusted error (%fsr) code 10v range 5v range +10v range +5v range +10v range with dcdc av dd = +15v av ss = ?15v t a = 25c 09226-025 figure 10 . total unadjusted error vs. dac code ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 ?40 ?20 0 20 40 60 80 100 inl error (%fsr) tempera ture (c) +5v range max inl +10v range max inl 5v range max inl 10v range max inl +5v range min inl +10v range min inl 5v range min inl 10v range min inl av dd = +15v av ss = ?15v output unloaded 09226-127 figure 11 . integral nonlinearity error vs. temperature ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 ?40 ?20 0 20 40 60 80 100 dnl error (lsb) temperature (c) av dd = +15v av ss = ?15v all ranges dnl error max dnl error min 09226-128 figure 12 . differential nonlinearity error vs. temperature ?0.006 ?0.004 ?0.002 0 0.002 0.004 0.006 0.008 0.010 0.012 ?40 ?20 0 20 40 60 80 100 total unadjusted error (%fsr) tempera ture (c) av dd = +15v av ss = ?15v output unloaded +5v range +10v range 5v range 10v range 09226-129 figure 13 . total unadjusted error vs. temperature
data sheet AD5755-1 rev. e | page 17 of 52 ?0.035 ?0.030 ?0.025 ?0.020 ?0.015 ?0.010 ?0.005 0 ?40 ?20 0 20 40 60 80 100 total unadjusted error (%fsr) tempera ture (c) av dd = +15v av ss = 0v output unloaded +5v range +12v range 09226-130 figure 14 . total unadjust ed error vs. temperature, single supply ?0.006 ?0.004 ?0.002 0 0.002 0.004 0.006 0.008 0.010 0.012 ?40 ?20 0 20 40 60 80 100 full-scale error (%fsr) tempera ture (c) av dd = +15v av ss = ?15v output unloaded +5v range +10v range 5v range 10v range 09226-132 figure 15 . full - scale error vs. temperature ?0.0025 ?0.0020 ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 ?40 ?20 0 20 40 60 80 100 offset (%fsr) tempera ture (c) av dd = +15v av ss = ?15v output unloaded +5v range +10v range 09226-133 figure 16 . offset error vs. temperature ?0.0020 ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 0.0020 0.0025 ?40 ?20 0 20 40 60 80 100 bipolar zero error (%fsr) tempera ture (c) av dd = +15v av ss = ?15v output unloaded 5v range 10v range 09226-134 figure 17 . bipolar zero error vs. temperature ?0.006 ?0.004 ?0.002 0 0.002 0.004 0.006 0.008 0.010 ?40 ?20 0 20 40 60 80 100 tempera ture (c) av dd = +15v av ss = ?15v output unloaded +5v range +10v range 5v range 10v range gain error (%fsr) 09226-135 figure 18 . gain error vs. temperature ?0.0020 ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 zero-scale error (%fsr) av dd = +15v av ss = ?15v output unloaded +5v range +10v range 5v range 10v range 09226-136 ?40 ?20 0 20 40 60 80 100 tempera ture (c) figure 19 . zero - scale error vs. temperature
AD5755-1 data sheet rev. e | page 18 of 52 0.0020 ?0.0020 10 15 20 25 30 inl eror (%fsr) supply (v) 09226-034 ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 0v to 10v range max inl 0v to 10v range min inl t a = 25c av ss = ?26.4v for av dd > +26.4v figure 20 . integral nonlinearity error vs. av dd /|av ss | ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 10 15 20 25 30 dnl error (lsb) supply (v) av ss = ?26.4v for av dd > +26.4v av dd = +15v av ss = ?15v all ranges t a = 25c dnl error max dnl error min 09226-138 figure 21 . differential nonlinearity error vs. av dd /|av ss | 0.008 0.006 0.004 0.002 0 ?0.008 ?0.004 10 15 20 25 30 total unadjusted error (%fsr) supply (v) 09226-035 0v to 10v range max tue 0v to 10v range min tue t a = 25c av ss = ?26.4v for av dd > +26.4v figure 22 . total unadjusted error vs. av dd /|av ss | 0.0020 0.0015 0.0010 0.0005 0 ?0.0005 ?0.0010 ?0.0015 ?0.0020 ?20 201612 840 ?4?8?12?16 output voltage delta (v) output current (ma) 09226-036 8ma limit, code = 0xffff 16ma limit, code = 0xffff av dd = +15v av ss = ?15v 10v range t a = 25c figure 23 . source and sink capability of output amplifier 12 8 4 0 ?4 ?8 ?12 ?5 15 10 5 0 output voltage (v) time (s) 09226-037 av dd = +15v av ss = ?15v 10v range t a = 25c output unloaded figure 24 . full - scale positive step 12 8 4 0 ?4 ?8 ?12 ?5 15 10 5 0 output voltage (v) time (s) 09226-038 av dd = +15v av ss = ?15v 10v range t a = 25c output unloaded figure 25 . full - scale negative step
data sheet AD5755-1 rev. e | page 19 of 52 15 10 5 0 ?5 ?10 ?15 ?20 0 5 4 3 2 1 output voltage (v) time (s) 09226-039 0x7fff t o 0x8000 0x8000 t o 0x7fff the externa l resis t or is a vishay s102c, 0.6ppm resis t or av dd = +15v av ss = ?15v 10v range t a = 25c figure 26 . digital -to- analog glitch 15 10 5 0 ?5 ?10 ?15 0 7 8 9 10 5 6 1 2 3 4 output voltage (v) time (s) 09226-040 av dd = +15v av ss = ?15v 10v range t a = 25c output unloaded figure 27 . peak -to- peak noise (0.1 hz to 10 hz bandwidth) 300 200 100 0 ?100 ?200 ?300 0 7 8 9 10 5 6 1 2 3 4 output voltage (v) time (s) 09226-041 av dd = +15v av ss = ?15v 10v range t a = 25c output unloaded figure 28 . peak -to- peak noise (100 khz bandwidth) 25 20 15 10 5 0 ?5 ?10 ?15 ?20 ?25 0 25 50 75 100 125 output voltage (mv) time (s) 09226-043 av dd = +15v av ss = ?15v t a = 25c figure 29 . v out_x vs. time on power - up 60 40 20 0 ?20 ?40 ?60 ?80 ?100 ?120 ?140 0 2 4 6 8 10 output voltage (mv) time (s) 09226-044 poc = 1 poc = 0 av dd = +15v av ss = ?15v 10v range t a = 25c int_enable = 1 figure 30 . v out_x vs. time on output enable 0 ?120 ?100 ?80 ?60 ?40 ?20 10 100 1k 10k 100k 1m 10m v out_x psrr (db) frequency (hz) 09226-045 av dd = +15v v boost = +15v av ss = ?15v t a = 25c figure 31 . v ou t_x psrr vs. frequency
AD5755-1 data sheet rev. e | page 20 of 52 current outputs ?0.0025 ?0.0015 ?0.0005 0.0005 0.0015 0.0025 0 10000 20000 30000 40000 50000 60000 in l error (%fsr) code av dd = +15v av ss = ?15v t a = 25c 4m a t o 20ma, externa l r set 4m a t o 20ma, externa l r set , with dc- t o-dc converter 4m a t o 20ma, interna l r set 4m a t o 20ma, interna l r set , with dc- t o-dc converter 09226-149 figure 32 . integral nonlinearity vs. code 0 10000 20000 30000 40000 50000 60000 dn l error (lsb) code av dd = +15v av ss = ?15v t a = 25c 09226-150 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 4m a t o 20ma, externa l r set 4m a t o 20ma, externa l r set , with dc- t o-dc converter 4m a t o 20ma, interna l r set 4m a t o 20ma, interna l r set , with dc- t o-dc converter figure 33 . differential nonlinearity vs. code 0 10000 20000 30000 40000 50000 60000 total unadjusted error (%fsr) code 09226-151 ?0.015 ?0.010 ?0.005 0 0.005 0.010 0.015 0.020 0.025 0.030 0.035 av dd = +15v av ss = ?15v t a = 25c all channels enabled 4ma to 20ma, external r set 4ma to 20ma, external r set , with dc- t o-dc converter 4ma to 20ma, internal r set 4ma to 20ma, internal r set , with dc- t o-dc converter figure 34 . total unadjusted error vs. code ?0.0010 ?0.0008 ?0.0006 ?0.0004 ?0.0002 0 0.0002 0.0004 0.0006 0.0008 0.0010 in l error (%fsr) 4ma to 20ma range max inl 0ma to 20ma range max inl 0ma to 24ma range max inl 4ma to 20ma range max inl 0ma to 24ma range min inl 0ma to 20ma range min inl av dd = +15v av ss = ?15v/0v ?40 ?20 0 20 40 60 80 100 tempera ture (c) 09226-152 figure 35 . integral nonlinearity vs. temperature, internal r set ?0.0020 ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 0.0020 in l error (%fsr) 4ma to 20ma range max inl 0ma to 20ma range max inl 0ma to 24ma range max inl 4ma to 20ma range min inl 0ma to 24ma range min inl 0ma to 20ma range min inl ?40 ?20 0 20 40 60 80 100 tempera ture (c) av dd = +15v av ss = ?15v/0v 09226-153 figure 36 . integral nonlinearity vs. temperature, external r set ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 ?40 ?20 0 20 40 60 80 100 dnl error (lsb) temperature (c) av dd = +15v av ss = ?15v/0v all ranges internal and external r set dnl error max dnl error min 09226-154 figure 37 . differential nonlinearity vs. temperature
data sheet AD5755-1 rev. e | page 21 of 52 ?0.08 ?0.07 ?0.06 ?0.05 ?0.04 ?0.03 ?0.02 ?0.01 0 0.01 0.02 0.03 total unadjsuted error (%fsr) ?40 ?20 0 20 40 60 80 100 tempera ture (c) av dd = +15v av ss = ?15v/0v 4ma to 20ma internal r set 4ma to 20ma external r set 0ma to 20ma internal r set 0ma to 20ma external r set 0ma to 24ma external r set 0ma to 24ma internal r set 09226-155 figure 38 . total unadjusted error vs. temperature ?0.08 ?0.07 ?0.06 ?0.05 ?0.04 ?0.03 ?0.02 ?0.01 0 0.01 0.02 0.03 full-scale error (%fsr) ?40 ?20 0 20 40 60 80 100 tempera ture (c) av dd = +15v av ss = ?15v/0v 4ma to 20ma internal r set 4ma to 20ma external r set 0ma to 20ma internal r set 0ma to 20ma external r set 0ma to 24ma external r set 0ma to 24ma internal r set 09226-157 figure 39 . full scale error vs. temperature ?0.020 ?0.015 ?0.010 ?0.005 0 0.005 0.010 0.015 0.020 offset error (%fsr) ?40 ?20 0 20 40 60 80 100 tempera ture (c) 4ma to 20ma internal r set 4ma to 20ma external r set 0ma to 20ma internal r set 0ma to 20ma external r set 0ma to 24ma external r set 0ma to 24ma internal r set av dd = +15v av ss = ?15v/0v 09226-158 figure 40 . offset error vs. temperature ?0.06 ?0.05 ?0.04 ?0.03 ?0.02 ?0.01 0 0.01 0.02 gain error (%fsr) ?40 ?20 0 20 40 60 80 100 tempera ture (c) 4ma to 20ma internal r set 4ma to 20ma external r set 0ma to 20ma internal r set 0ma to 20ma external r set 0ma to 24ma external r set 0ma to 24ma internal r set av dd = +15v av ss = ?15v/0v 09226-159 figure 41 . gain error vs. temperature ?0.0020 ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 0.0020 0.0025 10 15 20 25 30 in l error (%fsr) supply (v) 4ma to 20ma range max inl 4ma to 20ma range min inl t a = 25c av ss = ?26.4v for av dd > +26.4v 09226-056 figure 42 . integral nonlinearity error vs. av dd /|av ss |, over supply, external r set ?0.0020 ?0.0025 ?0.0015 ?0.0010 ?0.0005 0 0.0005 0.0010 0.0015 10 15 20 25 30 in l error (%fsr) supply (v) 4ma to 20ma range max inl 4ma to 20ma range min inl t a = 25c av ss = ?26.4v for av dd > +26.4v 09226-057 figure 43 . integral nonlinearity error vs. av dd /|av ss |, over supply, internal r set
AD5755-1 data sheet rev. e | page 22 of 52 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 1.0 10 15 20 25 30 dnl error (lsb) supply (v) dnl error max dnl error min 09226-162 av ss = ?26.4v for av dd > +26.4v all ranges internal and external r set t a = 25c figure 44 . differential nonlinearity error vs. av dd 0 0.002 0.004 0.006 0.008 0.010 0.012 10 15 20 25 30 total unadjusted error (%fsr) supply (v) 4ma to 20ma range max tue 4ma to 20ma range min tue t a = 25c av ss = ?26.4v for av dd > +26.4v 09226-060 figure 45 . total unadjusted error vs. av dd , external r set 10 15 20 25 30 total unadjusted error (%fsr) supply (v) 4ma to 20ma range max tue 4ma to 20ma range min tue t a = 25c av ss = ?26.4v for av dd > +26.4v ?0.020 ?0.018 ?0.016 ?0.014 ?0.012 ?0.010 ?0.008 ?0.006 ?0.004 ?0.002 0 09226-061 figure 46 . total unadjusted error vs. av dd , internal r set 6 5 4 3 2 1 0 0 20 15 10 5 current (a) time (s) 09226-062 av dd = +15v av ss = ?15v t a = 25c r load = 300? figure 47 . output current vs. time on power - up 4 ?10 ?8 ?6 ?4 ?2 0 2 0 1 2 3 4 5 6 current (a) time (s) 09226-063 av dd = +15v av ss = ?15v t a = 25c r load = 300? int_en = 1 figure 48 . output current vs. time on output enable 0 5 10 15 20 25 30 output current (ma) ?0.50 ?0.25 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 time (ms) 0ma to 24ma range 1k? load f sw = 410khz inductor = 10h (xal4040-103) av cc = 5v t a = 25c 09226-167 i out v boost figure 49 . output current and v boost _x settling time with dc -to- dc converter (see figure 80 )
data sheet AD5755-1 rev. e | page 23 of 52 0 5 10 15 20 25 30 output current (ma) ?0.25 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 time (ms) 09226-168 i out , t a = ?40c i out , t a = +25c i out , t a = +105c 0ma to 24ma range 1k? load f sw = 410khz inductor = 10h (xal4040-103) av cc = 5v figure 50 . output current settling with dc -to- dc converter vs. time and temperature (see figure 80 ) 0 5 10 15 20 25 30 output current (ma) ?0.25 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 time (ms) 09226-169 i out , av cc = 4.5v i out , av cc = 5.0v i out , av cc = 5.5v 0ma to 24ma range 1k? load f sw = 410khz inductor = 10h (xal4040-103) t a = 25c figure 51 . output current settling with dc -to- dc converter vs. time and av cc (see figure 80 ) ?10 ?8 ?6 ?4 ?2 0 2 4 6 8 10 0 2 4 6 8 10 12 14 current (ac coupled) (a) time (s) av cc = 5v f sw = 410khz inductor = 10h (xal4040-103) 0ma to 24ma range 1k? load external r set t a = 25c 20ma output 10ma output 09226-170 figure 52 . output current vs. time with dc -to- dc converter (see figure 80 ) 8 7 6 5 4 3 2 1 0 0 5 10 15 20 headroom voltage (v) current (ma) 09226-067 0ma to 24ma range 1k? load f sw = 410khz inductor = 10h (xal4040-103) t a = 25c figure 53 . dc -to- dc converter headroom vs. output current (see figure 80 ) 0 ?120 ?100 ?80 ?60 ?40 ?20 10 100 1k 10k 100k 1m 10m i out_x psrr (db) frequency (hz) 09226-068 av dd = +15v v boost = +15v av ss = ?15v t a = 25c figure 54 . i out_x psrr vs. frequency
AD5755-1 data sheet rev. e | page 24 of 52 dc- to - dc block 90 85 80 75 70 65 60 55 50 0 24 20 16 12 8 4 v boost_x efficiency (%) current (ma) 09226-016 0ma to 24ma range 1k? load external r set f sw = 410khz inductor = 10h (xal4040-103) t a = 25c av cc = 4.5v av cc = 5v av cc = 5.5v figure 55 . efficiency a t v boost_x vs. output current (see figure 80 ) 90 85 80 75 70 65 60 55 50 ?40 100 40 60 80 20 0 ?20 v boost_x efficiency (%) temperature (c) 09226-017 09226-017 0ma to 24ma range 1k? load external r set av cc = 5v f sw = 410khz inductor = 10h (xal4040-103) 20m a figure 56 . efficiency at v boost_x vs. temperature (see figure 80 ) 80 70 60 50 40 30 20 0 24 20 16 12 8 4 i out_x efficiency (%) current (ma) 09226-018 0ma to 24ma range 1k? load external r set f sw = 410khz inductor = 10h (xal4040-103) t a = 25c av cc = 4.5v av cc = 5v av cc = 5.5v figure 57 . output efficiency vs. output current (see figure 80 ) 80 70 60 50 40 30 20 ?40 100 40 60 80 20 0 ?20 i out_x efficiency (%) temperature (c) 09226-019 0ma to 24ma range 1k? load external r set av cc = 5v f sw = 410 khz inductor = 10h (xal4040-103) 20m a figure 58 . output efficiency vs. temperature (see figure 80 ) 0 0.1 0.2 0.3 0.4 0.5 0.6 ?40 ?20 0 20 40 60 80 100 switch resis t ance (?) tempera ture (c) 09226-123 figure 59 . switch resistance vs. temperature
data sheet AD5755-1 rev. e | page 25 of 52 refere nce 16 14 12 10 8 6 4 2 0 ?2 0 0.2 0.4 0.6 0.8 1.0 1.2 voltage (v) time (ms) 09226-010 av dd ref out t a = 25c figure 60 . refout turn - on transient 4 3 2 1 0 ?1 ?2 ?3 0 2 4 6 8 10 refout (v) time (s) 09226-011 av dd = 15v t a = 25c figure 61 . refout output noise (0.1 hz to 10 hz bandwidth) 150 100 50 0 ?50 ?100 ?150 0 5 10 15 20 refout (v) time (ms) 09226-012 av dd = 15v t a = 25c figure 62 . refout output noise (100 khz bandwidth) 5.0000 5.0005 5.0010 5.0015 5.0020 5.0025 5.0030 5.0035 5.0040 5.0045 5.0050 ?40 ?20 0 20 40 60 80 100 refout (v) tempera ture (c) 30 devices shown av dd = 15v 09226-163 figure 63 . refout vs. temperature ( when the ad5755 -1 is soldered onto a pcb, the reference shifts due to thermal shock on the package. the average output voltage shift is ?4 mv. measurement of these parts after seven days shows that the outputs typically shift back 2 mv toward their initial value s. this second shift is due to the relaxation of stress incurred during soldering.) 5.002 5.001 5.000 4.999 4.998 4.997 4.996 4.995 0 2 4 6 8 10 refout (v) load current (ma) 09226-014 av dd = 15v t a = 25c figure 64 . refout vs. load current 5.00000 4.99995 4.99990 4.99980 4.99985 4.99975 4.99970 4.99965 4.99960 10 15 20 25 30 refout (v) av dd (v) 09226-015 t a = 25c figure 65 . refout vs. supply
AD5755-1 data sheet rev. e | page 26 of 52 general 450 400 350 300 250 200 150 100 50 0 0 1 2 3 4 5 di cc (a) sdin voltage (v) 09226-007 dv cc = 5v t a = 25c figure 66 . di cc vs . logic input voltage 10 8 6 4 2 0 ?12 ?10 ?8 ?6 ?4 ?2 10 15 20 25 30 current (ma) voltage (v) 09226-008 ai dd ai ss t a = 25c v out = 0v output unloaded figure 67 . ai dd /ai ss vs. av dd /|av ss | 8 7 0 1 2 3 4 5 6 current (ma) voltage (v) 09226-009 ai dd t a = 25c i out = 0ma 10 15 20 25 30 figure 68 . ai dd vs. av dd 13.4 13.3 13.2 13.1 13.0 12.9 12.8 12.7 12.6 ?40 ?20 0 20 40 60 80 100 frequency (mhz) temperature (c) 09226-020 dv cc = 5.5v figure 69 . internal oscillator frequency vs. temperature 14.4 14.2 14.0 13.8 13.6 13.4 13.2 13.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 frequency (mhz) voltage (v) 09226-021 dv cc = 5.5v t a = 25c figure 70 . internal oscillator frequency vs. dv cc supply voltage
data sheet AD5755-1 rev. e | page 27 of 52 terminology relative accuracy or integral nonlinearity (inl) for the dac, relative accuracy, or integral nonlinear ity , is a measure of the maximum deviation, in lsbs, from the best fit line th r ough the dac transfer function. a typical inl vs. code plot is shown in figure 8 . differential nonlinearity (dnl) differential nonlinearity (dnl) is the difference between the measured change and the ideal 1 lsb change be tween any two adjacent codes. a specified differential nonlinearity of 1 lsb maximum ensures monotonicity. this dac is guaranteed monotonic by design. a typical dnl vs. code plot is shown in figure 9 . monotonicity a dac is monoto nic if the output either increases or remains constant for increasing digital input code. the ad5755 -1 is monotonic over its full operating temperature range. negative full - scale error/zero - scale error negative full - scale error is the error in the dac outp ut voltage when 0x0000 (straight binary coding) is loaded to the dac register. zero - scale tc this is a measure of the change in zero - scale error with a change in temperature. zero - scale error tc is expressed in ppm fsr/c. bipolar zero error bipolar zero error is the deviation of the analog output from the ideal half - scale output of 0 v when the dac register is loaded with 0x8000 (straight binary coding) . bipolar zero tc bipolar zero tc is a measure of the change in the bipolar zero error with a change in temperature. it is expressed in ppm fsr/c. offset error in voltage output mode, offset error is the deviation of the analog output from the ideal quarter - scale output when in bipolar output ranges and the dac register is loaded with 0x 4 000 (straight binar y coding). in current output mode, offset error is the deviation of the analog output from the ideal zero - scale output when all dac registers are loaded with 0x0000. gain error this is a measure of the span error of the dac. it is the devia - tion in slope o f the dac transfer characteristic from the ideal, expressed in % fsr. gain tc this is a measure of the change in gain error with changes in temperature. gain tc is expressed in ppm fsr/c. full - scale error full -s cale error is a measure of the output error when full - scale code is loaded to the dac register. ideally, the output should be full - scale ? 1 lsb. full - scale error is expressed in percent of full - scale range (% fsr). full - scale tc full - scale tc is a measure of the change in full - scale error with changes in temperature and is expressed in ppm fsr/c. total unadjusted erro r total unadjusted error (tue) is a measure of the output error taking all the various errors into account, including inl error, offset error, gain error , temperature, and time. tue is expressed in % fsr. dc crosstalk this is the dc change in the output l evel of one dac in response to a change in the output of another dac. it is measured with a full - scale output change on one dac while monitoring another dac, which is at midscale. current loop compliance voltage the maximum voltage at the i out _x pin for wh ich the output current is equal to the programmed value. voltage reference thermal hysteresis voltage reference thermal hysteresis is the difference in output voltage measured at +25c compared to the output voltage measured at +25c after cycling the temp erature from +25c to ?40c to +105c and back to +25c. the hysteresis is specified for the first and second temperatu re cycles and is expressed in ppm . output voltage settling time output voltage settling time is the amount of time it takes for the outpu t to settle to a specified level for a full - scale input change. a plot of settling time is shown in figure 24, figure 50, and figure 51. slew rate the slew rate of a device is a limitation in the rate of change of the output voltage. the output slewing speed of a voltage - output digital - to - analog converter is usually limited by the slew rate of the amplifier used at its output. slew rate is measured from 10% to 90% of the output si gnal and is given in v/s. power - on glitch energy power - on glitch energy is the impulse injected into the analog output when the ad5755 -1 is powered - on. it is specified as the area of the glitch in nv - sec. see figure 29 and figure 47 . digital - to - analog glitch impulse digital - to - analog glitch impulse is the impulse injected into the analog output when the input code in the dac register changes state, but the output voltage remains constant. it is normally s pecified as the area of the glitch in nv - sec and is measured when the digital input code is changed by 1 lsb at the major carry transition ( ~ 0x7fff to 0x8000). see figure 26 .
AD5755-1 data sheet rev. e | page 28 of 52 glitch impulse peak amplitude glitch impulse peak ampl itude is the peak amplitude of the impulse injected into the analog output when the input code in the dac register changes state. it is specified as the amplitude of the glitch in mv and is measured when the digital input code is changed by 1 lsb at the ma jor carry transition ( ~ 0x7fff to 0x8000). see figure 26 . digital feedthrough digital feedthrough is a measure of the impulse injected into the analog output of the dac from the digital inputs of the dac but is measured when the da c output is not updated. it is specified in nv - sec and measured with a full - scale code change on the data bus. dac -to - dac crosstalk dac - to - dac crosstalk is the glitch impulse transferred to the output of one dac due to a digital code change and a subsequen t output change of another dac. this includes both digital and analog crosstalk. it is measured by loading one of the dacs with a full - scale code change (all 0s to all 1s and vice versa) with ldac low and monitoring the output of ano ther dac. the energy of the glitch is expressed in nv - sec. power supply rejection ratio (psrr) psrr indicates how the output of the dac is affected by changes in the power supply voltage. reference tc reference tc is a measure of the change in the referenc e output voltage with a change in temperature. it is expressed in ppm/c. line regulation line regulation is the change in reference output voltage due to a specified change in supply voltage. it is expressed in ppm/v. load regulation load regulation is t he change in reference output voltage due to a specified change in load current. it is expressed in ppm/ma. dc -to - dc converter headroom this is the difference between the voltage required at the current output and the voltage supplied by the dc - to - dc conve rter. see figure 53 . output efficiency cc cc load aiav ri out 2 this is defined as the power delivered to a channels load vs . the power delivered to the channel s dc - to - dc input. efficiency at v boost_x cc cc xboost out aiav vi _ this is defined as the power delivered to a channels v boost _x supply vs . the power delivered to the channel s dc - to - dc input. the v boost _x quiescent current is considered part of the dc - to - dc converters losses.
data sheet AD5755-1 rev. e | page 29 of 52 theory of operation the ad5755 -1 is a quad, p recision digital - to - current loop and voltage output converter designed to meet the requirements of industrial process control applications. it provides a high precision, fully integrated, low cost , single- chip solution for generating current loop and unip olar/bipolar voltage outputs. t he current ranges available are 0 ma to 20 ma, 0 ma to 24 ma , and 4 ma to 20 ma . the voltage ranges available are 0 v to 5 v, 5 v, 0 v to 10 v, and 10 v. the current and voltage outputs are availa - ble on separate pins , and only one is active at any one time. the desired output configuration is user selectable via the dac c ontrol register. on- chip dynamic power control minimizes package power dissipation in current mode. dac architecture the dac core architecture of the ad575 5-1 consists of two matched dac sections. a simplified circuit diagram is shown in figure 71 . the four msbs of the 16 - bit data - word are decoded to drive 15 switches, e1 to e15. each of these switches connects one of 15 matched res istors to either ground or the reference b uffer output. the remaining 12 bits of the data - word drive switch s0 to switch s11 of a 12 - bit voltage mode r - 2r ladder network. 12-bit r-2r ladder four msbs decoded into 15 equal segments 2r 2r s0 s1 s7/s11 e1 e2 e15 v out 2r 2r 2r 2r 2r 09226-069 figure 71 . dac ladder structure the voltage output from t he dac core is either converted to a current (see figure 73 ), which is then mirrored to the supply rail so that the application simply sees a current source output , or it is buffered and scaled to output a soft ware selectable unip olar or bipolar voltage range ( see figure 72 ). both the voltage and current output s are supplied by v boost _x . the current and voltage are output on separate pins and cannot be output simultaneously. a channel s current and voltag e output pins can be tied together. 09226-070 range scaling dac v out_x short f au lt +v sense_x v out_x figure 72 . voltage output 09226-071 16-bit dac v boost_x r2 t2 t1 r3 i out_x r set a1 a2 figure 73 . voltage -to- current conversion circuitry voltage output amplifier the voltage output amplifier is capable of generating both unipo lar and bipolar output voltages. it is capable of driving a load of 1 k? in parallel with 1 f (with an external compen - sation capacitor) to agnd . the source and sink capabilities of the output amplifier are shown in figure 23 . th e slew rate is 1.9 v/s with a full - scale settling time of 16 s (10 v step). if remote sensing of the load is not required, connect +v sense _x directly to v out _x . + v sense_x must stay within 3.0 v of v out _x for correct operation. driving large capacitive loads the voltage output amplifier is capable of dri ving capacitive loads of up to 2 f with the addition of a 220 pf nonpolarized compensation capacitor on each channel. care should be taken to choose an appropriate value of compensation capacitor. this capacitor, while allowing the ad5755 -1 to drive higher cap aci - tive loads and reduce overshoot, increase s the settling time of the part and , therefore , a ffect s the bandwidth of the system. without the compensation capacitor, up to 10 nf capacitive loads can be driven. see table 5 for information on connecting compensa tion capacitors. reference buffers the ad5755 -1 can operate with either an external or internal reference. the reference input requires a 5 v reference for specified p erformance . this input voltage is then buffered before it is applied to the dac. power - on state of the ad5755 -1 on initial power - up of the ad5755 -1, the power - on reset circuit powers up in a state that is dependent on the power - on condition ( poc ) pin. if poc = 0 , the voltage output and current output channels power up in t ristate mode. if poc = 1 , the voltage output channel p ower s up with a 30 k ? pull - down resistor to g round, and the current output channel power s up to tri state. even though the output ranges are not enabled, the default output range is 0 v to 5 v, and the c lear c ode r egister is loaded
AD5755-1 data sheet rev. e | page 30 of 52 with all zeros. this means that if the user clears the part after power - up , the output is actively driven to 0 v (i f the channel has been enabled for clear) . after a device power on, or a device reset, it is recommended to wait 100 s or more before writing to the device to allow time for internal ca librations to take place. serial interface the ad5755 -1 is controlled over a versatile 3 - wire serial interface that operates at clock rates of up to 30 mhz and is compatible with spi , qspi, microwire, and dsp standards. data coding is always straight binar y. input shift register the input shift register is 24 bits wide. data is loaded into the device msb first as a 24 - bit word under the control of a serial clock input, sclk. data is clocked in on the falling edge of sclk. if packet error checking, or pec ( see the device features section) , is enabled , an additional eight bits must be written to the ad5755 - 1, creating a 32 - bit serial interface. there are two ways in which the dac ou tputs can be updated: individual updating or simulta neous updating of all dacs . individual dac updating in this mode, ldac is held low while data is being clocked into the dac d ata r egister. the addressed dac output is updated on the rising edge of sync . see table 3 and figure 3 for timing information. simultaneous updating of all dacs in this mode, ldac is held high while data is being clocked into the dac d ata r egister. only the first wri te to each channel s dac data register is valid after ldac is brought high. any subse - quent writes while ldac is still held high are ignored, though they are loaded into the dac data register. all the dac outpu ts are updated by taking ldac low after sync is taken high. v out_x dac register interface logic output i/v amplifier ldac sdo sdin 16-bit dac v refin sync dac data register offset and gain calibration dac input register sclk 09226-072 figure 74 . simplified serial interface of input loading circuitry for one dac channel transfer function table 6 shows the input code to ideal output voltage relationship for the ad5755 - 1 for straight binary data coding of the 10 v output range. table 6 . ideal output voltage to input code relationship digital input straight binary data coding analog output msb lsb v out 1111 1111 1111 1111 +2 v ref (32 , 767/32 , 768) 1111 1111 1111 1110 +2 v ref (32 , 766/32 , 768) 1000 0000 0000 0000 0 v 0000 0000 0000 0001 ?2 v ref (32,767/32,768) 0000 0000 0000 0000 ?2 v ref
data sheet AD5755-1 rev. e | page 31 of 52 registers table 7 shows an overview of the r egisters for the ad5755 -1. table 7 . data , control , and readback registers for the ad5755 -1 register description data dac data register ( 4) used to write a dac code to each dac channel. ad5755 -1 d ata bits = d15 to d0 . there are four dac d ata r egisters, one per dac c hannel. gain register ( 4) used to program gain trim , on a per channel basis. ad5755 -1 data bits = d15 to d0. there are four g ain r egisters, one per dac c hannel. offset register ( 4) used to program offset trim, on a per channel basis. ad5755 -1 data bits = d15 to d0. there are four o ffset r egisters, one per dac channel. clear code register ( 4) used to program c lear c ode on a per channel basis. ad5755 -1 data bits = d15 to d0. there are four c lear c ode r egisters, one per dac channel. control main control register used to c onfigure the part for main operation. sets functions such as status readback during write, enable s output on all channels simultaneously, power s on all dc -to - dc converter blocks simultaneously, and enables and sets conditions of the watchdog timer. see the device features s ection for more details. software register has three functions. used to perform a rese t, to toggle the user bit , and, as part of the watchdog timer feature, to verify correct data communication operation. slew rate control register ( 4) use d to program the slew rate of the output. there are four s lew r ate c ontrol r egisters, one per channel . dac control register ( 4) these registers are used to control the following : set the output range, for example, 4 ma to 20 ma , 0 v to 10 v. set whether an i nternal/ e xternal sense r esistor is used . en able/disable a channel for clear. enable/ d isable over range. enable/disable internal circuitry on a per channel basis. enable/ d isable output on a per chann el basis. power on dc -to - dc converter s on a per channel basis. there are four dac c ontrol r egisters, one per dac channel. dc -to - dc control register use t o set the dc - to - dc c ontrol parameters. can control dc -to - dc max imum voltage, phase , and frequency. readback status register this contains any fault information, as well as a user toggle bit.
AD5755-1 data sheet rev. e | page 32 of 52 programming sequence to write/enable the output correctly to correctly write to a nd set up the part from a power - on condition , use the following sequence: 1. perform a hardware or sof tware reset after initial power - on. 2. the dc - to - dc converter supply block must be configured. set the dc - to - dc switching frequency, ma x imum output voltage allowed , and the phase that the four dc - to - dc channels clock at. 3. configure the dac c ontrol r egister on a per channel basis. the output range is selected, and the dc - to - dc converter block is enabled (dc_dc bit) . other control bits can be configured at this point . set the int_enable bit; however, the output enable bit (outen) should not be set. 4. write the required code to the dac data r egister. this implement s a full dac calibration internally. allow at least 200 s before step 5 for redu ced output glitch. 5. write to the dac c ontrol r egister again to enable the out put (set the outen bit). a flow chart of this sequence is shown in figure 75. 09226-073 power on. step 1: perform a soft w are/hard w are rese t. step 4: write t o each/al l dac d at a registers. allow a t least 200s between ste p 3 and ste p 5 for reduced output glitch. step 2: write t o dc- t o-dc contro l register to set dc- t o-dc clock frequenc y , phase, and maximum vo lt age. step 3: write t o dac contro l register. select the dac channe l and output range. set the dc_dc bit and other contro l bits as required. set the int_enable bit but do not select the outen bi t. step 5: write t o dac contro l register. reload sequence as in ste p 3 above. this time select the outen bit t o enable the outpu t. figure 75 . programming sequence for enabling the output correctly changing and reprogr amming the range when changing between ranges , the same sequence as described in the programming sequence to write/enable the output correctly section should be used. it is recommended to set the rang e to its zero point (can be mid scale or zero scale) prior to disabling the output. because the dc - to - dc switching frequency, max imum voltage , and phase have already been selected, t here is no need to reprogram the s e. a flow chart of this sequence is shown in figure 76 . 09226-074 channe l ?s output is enabled. step 3: write v alue t o the dac d at a register. step 1: write t o channe l ?s dac d at a register. set the output t o 0v (zero or midscale). step 2: write t o dac contro l register. disable the output (outen = 0), and set the new output range. kee p the dc_dc bit and the int_enable bit se t. step 4: write t o dac contro l register. reload sequence as in ste p 2 above. this time select the outen bit to enable the outpu t. figure 76 . steps for changing the output range
data sheet AD5755-1 rev. e | page 33 of 52 data registers the input register is 24 bits wide. when pec is enabled , the input register is 32 bits wide, with the last eight bi ts correspond - ing to the pec code ( see the packet error checking section for more information on pec ). when writing to a data register , the format in table 8 must be used. dac data register when writing to the ad5755 - 1 dac data registers, d15 to d0 are used for dac data bits. table 10 shows the register format and table 9 describes the function of bit d23 to bit d16. table 8 . wr iting to a data register msb lsb d23 d22 d21 d20 d19 d18 d17 d16 d15 to d0 r/ w dut_ad1 dut_ad0 dreg2 dreg1 dreg0 dac_ad1 dac_ad0 data table 9 . input register decode bit description r/ w indicates a read from or a write to the addressed register. dut_ad1, dut_ad0 used in association with the e xternal p ins , ad1 and ad0 , to determine which ad5755 -1 device is being addressed by the system controller. it is not recommended to tie bo th ad1 and ad0 low when using pec, see the packet error checking section. dut_ad1 dut_ad0 function 0 0 addresses part with pin ad1 = 0, pin ad0 = 0 0 1 addresses part with pin ad1 = 0, pin ad0 = 1 1 0 addresses part with p in ad1 = 1, pin ad0 = 0 1 1 addresses part with pin ad1 = 1, pin ad0 = 1 dreg2, dreg1, dreg0 selects whether a data register or a control register is written to. if a control register is selected, a further decode of creg bits (see table 17) is required to select the particular control register, as follows . dreg2 dreg1 dreg0 function 0 0 0 write to dac data register (individual channel write) 0 1 0 write to gain register 0 1 1 write to gain register (all dacs) 1 0 0 wr ite to offset register 1 0 1 write to offset register (all dacs) 1 1 0 write to clear code register 1 1 1 write to a control register dac_ad1, dac_ad0 these bits are used to decode the dac channel . dac_ad1 dac_ad0 dac channel/ register address 0 0 dac a 0 1 dac b 1 0 dac c 1 1 dac d x x these are dont cares if they are not relevant to the operation being performed. table 10 . programming the dac data registers msb lsb d23 d22 d21 d20 d19 d18 d17 d16 d15 to d0 r/ w dut_ad1 dut_ad0 dreg2 dreg1 dreg0 dac_ad1 dac_ad0 dac data
AD5755-1 data sheet rev. e | page 34 of 52 gain register the 16- bi t g ain register, as shown in table 11, allows the user to adjust the gain of each channel in steps of 1 lsb . this is done by setting the dreg[2:0] bits to 010. it is possible to write the same gain code to all four dac channels at the same time by setting the dreg [2:0] bits to 011. the g ain r egister coding is straight binary as shown in table 12. the default code in the g ain r egister is 0x ffff . in theory , the gain can be tuned across the full range of the output. in practice, the maximum recom mended gain trim is about 50% of programmed range to maintain accuracy. see the digital offset and gain control section for more information. offset register the 16 - bit offset register , as shown in table 13 , allows the user to adjust the offset of each channel by ?32,768 lsbs to +32,767 lsbs in steps of 1 lsb . this is done by setting the dreg[2:0] bits to 100. it is possible to write the same offset code to all four dac channels at the same time by setting the dreg [2:0] bits to 101 . the o ffset r egister coding is straight binary as shown in table 14 . the default code in the o ffset r egister is 0x8000 , which result s in zero offset programmed to the output. see the digital offset and gain control section for more information. clear code register the 16 - bit cle ar code register allows the user to set the clear value of each channel as shown in table 15. it is po ssible, via software, to enable or disable on a per channel basis which channels are cleared when the clear pin is activated. th e default clear code is 0x0000. see the asynchronous clear section for more information. table 11 . programming the gain register r/ w dut_ad1 dut_ad0 dreg2 dreg1 dreg0 dac_ad1 dac_ad 0 d15 to d0 0 device address 0 1 0 dac channel address gain a djustment table 12 . gain register gain adjustment g15 g14 g13 g12 to g4 g3 g2 g1 g0 +65 , 535 lsbs 1 1 1 1 1 1 1 1 +65 , 534 lsbs 1 1 1 1 1 1 0 0 1 lsb 0 0 0 0 0 0 0 1 0 lsbs 0 0 0 0 0 0 0 0 table 13 . programming the offset register r/ w dut_ad1 dut_ad0 dreg2 dreg1 dreg0 dac_ad1 dac_ad0 d15 to d0 0 device address 1 0 0 dac channel address offset a djustmen t table 14 . offset register options offset adjustment of15 of14 of13 of12 to of4 of3 of2 of1 of0 +32 , 76 7 lsbs 1 1 1 1 1 1 1 1 +32 , 766 lsbs 1 1 1 1 1 1 0 0 no adjustment ( default ) 1 0 0 0 0 0 0 0 ?32 , 767 lsbs 0 0 0 0 0 0 0 0 ?32 , 768 lsbs 0 0 0 0 0 0 0 0 table 15 . programming the clear code register r/ w dut_ad1 dut_ad0 dreg2 dreg1 dreg0 dac_ad1 dac_ad0 d15 to d0 0 device address 1 1 0 dac channel a d dress c lear c ode
data sheet AD5755-1 rev. e | page 35 of 52 control registers when writing to a control register , the format shown in table 16 must be us ed. see table 9 for information on the configuration of bit d23 to bit d16. the contro l registers are addressed by setting the dreg [2:0] bits to 111 and then setting the creg [2:0] bits to the appropriate decode address for that register, according to table 17 . these creg bits select among the various control regist ers. main control register the main control register options are shown in table 18 and table 19 . see the device features section for more information on the features controlled b y the main c ontrol register. table 16 . writing to a control register msb lsb d23 d22 d21 d20 d19 d18 d17 d16 d15 d14 d13 d12 to d0 r/ w dut_ad1 dut_ad0 1 1 1 dac_ad1 dac_ad0 creg2 creg1 creg0 da ta table 17 . register access decode creg2 (d15) creg1 (d14) creg0 (d13) function 0 0 0 slew r ate c ontrol r egister (one per channel) 0 0 1 main c ontrol r egister 0 1 0 dac c ontrol r egister (one per channel) 0 1 1 dc -to - dc c ontrol r egister 1 0 0 software register table 18 . programming the main control register msb lsb d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 to d0 0 0 1 poc statread ewd wd1 wd0 x 1 shtcctlim outen _all dc dc _ all x 1 1 x = don t care. table 19 . main control register functions bit description poc the poc bit determines the state of the voltage output channel s during normal operation. its default value is 0. poc = 0. the output go es to the value set by the poc hardware pin when the voltage output is not enabled (default) . poc = 1. the output go es to the opposite value of the poc hardware pin if the voltage output is not enabled . statread enable status readback during a write. see the device features section. statread = 1, e nable . statread = 0, d isable (default) . ewd enable w atchdog t imer. see the device features section for more information. ewd = 1, e nable w atchdog . ewd = 0, d isable w atchdog (default) . wd1, wd0 timeout s elect b its. used to select the timeout period for the watchdog timer. wd1 wd0 timeout period (ms) 0 0 5 0 1 10 1 0 100 1 1 200 shtcctlim programmable short - circuit limit on the v out_x pin in the event of a short - circuit condit ion. 0 = 16 ma (default) . 1 = 8 ma . outen _all enables the output on all four dac s simultaneously. do not use the outen _ all bit when using the outen bit in the dac c ontrol register . dcdc _ all when set, p owers up the dc - to - dc converter on all four channels s imultaneously. to p ower down the dc -to - dc converters , all channel outputs must first be disabled. do not use the dc d c_ all bit when using the dc_dc bit in the dac control register .
AD5755-1 data sheet rev. e | page 36 of 52 dac control register the dac c ontrol r egister is used to configure each dac c hannel. the dac c ontrol register options are shown in table 20 and table 21. table 20 . programming dac control register d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 0 1 0 x 1 x 1 x 1 x 1 int_enable clr_en outen rset dc_ dc ovrng r2 r1 r0 1 x = dont care. table 21 . dac control register functions bit description int_enable powers up the dc - to - dc converter , dac , and internal amplifiers for the sel ected channel. does not enable the output. can only be done on a per channel basis. it is recommended to set this bit and allow a > 200 s delay before enabling the output because this result s in a reduced output enable glitch. see figure 30 and figure 48 for plots of this glitch. clr_en per channel c lear e nable bit. selects if this channel clear s when the clear pin is activated. clr_en = 1, channel clear s when the part is cleared. clr_en = 0, channel doe s not clear when the part is cleared (default) . outen enables/ d isables the selected output channel . outen = 1, e nables the channel . outen = 0, d isable s the channel (default) . rset selects an internal or external current sense resistor for the selected da c channel . rset = 0 , s elects the external r esistor (default) . rset = 1 , selects the i nternal r esistor . dc_dc powers the dc - to - dc converter on the selected channel. dc_dc = 1, p ower up the dc -to - dc converter . dc_dc = 0, p ower down the dc -to - dc converter (default) . this allows per channel dc - to - dc converter power - up/ power -d own. to power down the dc -to - dc converter , the outen and int_enable bits must also be set to 0. all dc -to - dc converters can also be powered up simultaneously using the dcdc_ all bit in t he m ain c ontrol r egister. ovrng enables 20% overrange on voltage output c hannel only. no current output overrange available. ovrng = 1, e nabled . ovrng = 0, d isabled (default) . r2, r1, r0 selects the output range to be enabled. r2 r1 r0 output range se lected 0 0 0 0 v to 5 v v oltage r ange (default) . 0 0 1 0 v to 10 v v oltage r ange . 0 1 0 5 v v oltage r ange . 0 1 1 10 v v oltage r ange . 1 0 0 4 ma to 20 ma c urrent r ange . 1 0 1 0 ma to 20 ma c urrent r ange . 1 1 0 0 ma to 24 ma c urrent r ange .
data sheet AD5755-1 rev. e | page 37 of 52 software register the s oftware r egister has three functions. it allows the user to perform a software reset to the part. it can be used to set the user toggle bit, d11 , in the s tatus register. it is also used as part of the watchdog feature when it is ena bled. this feature is useful to ensure that communication has not been lost between the mcu and the ad5755 -1 and that the datapath l ines are working properly (that is, sdi n, sclk , and sync ). when the watchdog feature is enabled , th e user must write 0x195 to the s oftware r egister within the timeout period. if this command is not received within the timeout period, the alert pin signal s a fault condition. this is only required when the w atchdog t imer function is enabled. dc - to - dc cont rol register the dc - to - dc control register allows the user control over the dc - to - dc switching frequency and phase, as well as the maximum allowable dc - to - dc output voltage. the dc - to - dc control register options are shown in table 24 and table 25. table 22 . programming the software register msb lsb d15 d14 d13 d12 d11 to d0 1 0 0 user p rogram reset code /spi code table 23 . software register functions bit description user program this bit is mapped to bit d11 of the s tatus r egister. when this bit is set to 1 , bit d11 of the s tatus r egister is set to 1. likewise , when d12 is set to 0 , bit d11 of the s tatus r egister is also set to zero. this feature can be used to ensure that the spi pins are working correctly by writing a known bit value to this register and reading back the corresponding bit from the s tatus r egister. reset code /spi code option description reset code writing 0x555 to d [11: 0] performs a reset of the ad5755 -1. spi code if the w atchdog t imer feature is enabled, 0x195 must be written to the s oftware register (d11 to d0) within the programmed timeout period . table 24 . programming the dc -to - dc control register msb lsb d15 d14 d13 d12 to d7 d6 d5 to d4 d3 to d2 d1 to d0 0 1 1 x 1 dc - dc comp dc - dc phase dc - dc freq dc - dc maxv 1 x = dont care. table 25 . dc -to - dc control register options bit description dc - dc comp selects between an internal and external compensation resistor for the dc - to - dc converter . see the dc - to - dc converter compensation capacitors and ai cc supply requirements slewing sections in the device features section for more information. 0 = s elects the internal 150 k ? compensation resistor (d efault) . 1 = b ypasses the internal compensation resistor for the dc -to - dc converter. in this mode , an external dc -to - dc compensation resistor must be used ; this is placed at the comp dcdc _x pin in series with the 10 nf dc -to - dc com pensation capacitor to ground. typically , a ~50 k? resistor is recommended . dc - dc phase user p rogrammable dc -to - dc converter p hase ( between c hannels) . 00 = a ll dc -to - dc converters clock on the same edge (default) . 01 = chan nel a and chan nel b clock on the same edge, chan nel c and chan nel d clock on opposite edge s. 10 = chan nel a and chan nel c clock on the same edge, chan nel b and chan nel d clock on opposite edge s. 11 = chan nel a, chan nel b, chan nel c, and chan nel d clock 90 out of phase from each other . dc - dc freq dc -to - dc s witching f requency ; these are divided down from the internal 13 mhz oscillator ( see figure 69 and figure 70 ). 00 = 250 10% kh z. 01 = 410 10% kh z (default) . 10 = 650 10% kh z. dc -dc maxv maximum allowed v boost _x voltage supplied by the dc - to - dc converter . 00 = 23 v + 1 v/ ?1 .5 v (default) . 01 = 24.5 v 1 v. 10 = 27 v 1 v. 11 = 29.5 v 1v .
AD5755-1 data sheet rev. e | page 38 of 52 slew rate control register this register is used to program the slew rate control for t he selected dac channel. this feature is available on both the current and voltage outputs. the slew rate control is enabled/ disabled and programmed on a per channel basis. see table 26 and the digital sl ew rate control section for more information. readback operation readback mode is invoked by setting the r/ w bit = 1 in the serial input register write. see table 27 for the bits associated with a readback operation. the dut_ad1 and dut_ad0 bits, in association with bits rd[4:0], select the register to be read. the remaining data bits in the write sequence are dont care s. during the next spi transfer (see figure 4 ), the data appea ring on the sdo output contains the data from the previously addressed register. this second spi transfer should either be a request to read yet another register on a third data transfer or a no operation command. the no operation command for dut address 00 is 0x1ce000, for other dut addresses , bits d22 and d21 are set accordingly. readback example to read back the gain register of device 1, channel a on the ad5755 -1, implement the following sequence: 1. write 0xa80000 to the ad5755 - 1 input register. this con figures the ad5755 - 1 device address 1 for read mode with the gain register of channel a selected. all the data bits, d15 to d0, are dont care s. 2. follow with another read command or a no operation command ( 0x3ce000 ). during this command, the data from the channel a gain register is clocked out on the sdo line. table 26 . programming the slew rate control register d15 d14 d13 d12 d11 to d7 d6 to d3 d2 to d0 0 0 0 sren x 1 sr_clock sr_step 1 x = dont care. table 27 . input shift register contents for a read operation d23 d22 d21 d20 d19 d18 d17 d16 d15 to d0 r/ w dut_ad1 dut_ad0 rd4 rd3 rd2 rd1 rd0 x 1 1 x = dont care. table 28 . read address decoding rd4 rd3 rd2 rd 1 rd0 function 0 0 0 0 0 read dac a d ata r egister 0 0 0 0 1 read dac b d ata r egister 0 0 0 1 0 read dac c d ata r egister 0 0 0 1 1 read dac d d ata r egister 0 0 1 0 0 read dac a control register 0 0 1 0 1 read dac b control register 0 0 1 1 0 re ad dac c control register 0 0 1 1 1 read dac d control register 0 1 0 0 0 read dac a gain register 0 1 0 0 1 read dac b gain register 0 1 0 1 0 read dac c gain register 0 1 0 1 1 read dac d gain register 0 1 1 0 0 read daca offset register 0 1 1 0 1 read dac b offset register 0 1 1 1 0 read dac c offset register 0 1 1 1 1 read dac d offset register 1 0 0 0 0 clear dac a code register 1 0 0 0 1 clear dac b code register 1 0 0 1 0 clear dac c code register 1 0 0 1 1 clear dac d code regi ster 1 0 1 0 0 dac a slew rate control register 1 0 1 0 1 dac b slew rate control register 1 0 1 1 0 dac c slew rate control register 1 0 1 1 1 dac d slew rate control register 1 1 0 0 0 read s tatus r egister 1 1 0 0 1 read m ain control r egister 1 1 0 1 0 read dc - to - dc control r egister
data sheet AD5755-1 rev. e | page 39 of 52 status register the s tatus r egister is a read only register. this register contains any fault information as a well as a ramp active bit and a u ser toggle b it. when the statread bit in the m ain c ontrol register is set , the s tatus r egister contents can be read back on the sdo pin during every write sequence. alternat iv ely, if the statread bit is not set , the s tatus register can be read using the normal readback operation. table 29 . decoding the status register msb lsb d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 dc - dcd dc - dcc dc - dcb dc - dca user toggle pec error ramp active over temp v out_d f ault v out_c f ault v out_b f ault v out_a f ault i out_d f ault i out_c f ault i out_b f ault i o ut_a f ault table 30 . status register options bit description dc - dcd in current output mode , this bit is set on channel d if the dc -to - dc convert er cannot maintain compliance (i t may be reaching its v max voltage). in this case , the i out_d f ault bit is also set. see the dc -to - dc converter v max functionality section for more information on this bit s operation under this condition. in v oltage output mode , this bit is set if , on channel d, the dc -to - dc convert er is unable to regulate to 15 v as expected. when this bit is set, it does not result in the fau lt pin going high. dc - dcc in current output mode, this bit is set on channel c if the dc - to - dc converter cannot maintain compliance (it may be reaching its v max voltage). in this case, the i out_ c fault bit is also set. see the dc -to - dc converter v max functionality section for more information on this bits operation under this condition. in voltage output mode , this bit is set if, on channel c, the dc -to - dc converter is unable to regulate to 15 v as expected. when this bit is set, it does not result in the fau lt pin going high. dc - dcb in current output mode, this bit is set on channel b if the dc -to - dc converter cannot maintain compliance (it may be reaching its v max voltage). in this case, the i out_ b fault bit is also set. see the dc - to - dc converter v max functionality section for more information on this bits operation unde r this condition. in voltage output mode, this bit is set if, on channel b , the dc -to - dc converter is unable to regulate to 15 v as expected. when this bit is set, it does not result in the fau lt pin going high. dc -dc a in current output mode, this bit is set on channel a if the dc -to - dc converter cannot maintain compliance (it may be reaching its v max voltage). in this case, the i out_ a fault bit is also set. see the dc -to - dc converter v max functionality section f or more information on this bits operation under this condition. in voltage output mode, this bit is set if, on channel a, the dc -to - dc converter is unable to regulate to 15 v as expected. when this bit is set, it does not result in the fau lt pin going high. user toggle user t oggle bit . this bit is set or cleared via the software register. this can be used to verify data communications if needed. pec error denot es a pec error on the last data - word received over the spi interface. ram p active this bit is set while any one of the output channels is slewing (slew rate control is enabled on at least one channel) . over temp this bit is set if the ad5755 -1 core temperature exceeds approx imately 150 c. v out_d fault this bit is set if a fau lt is detected on the v out _d pin. v out_c fault this bit is set if a fault is detected on the v out _c pin. v out_b fault this bit is set if a fault is detected on the v out _b pin. v out_a fault this bit is set if a fault is detected on the v out _a pin. i out_ d fault this bit is set if a fault is detected on the i out _d pin. i out_c fault this bit is set if a fault is detected on the i out _c pin. i out_b fault this bit is set if a fault is detected on the i out _ b pin. i out_a fault this bit is set if a fault is de tected on the i out _a pin.
AD5755-1 data sheet rev. e | page 40 of 52 device features output fault the ad5755 -1 is equipped with a fault pin, an active low open - drain output allowing several ad5755 -1 devices to be connected together to one pull - up resistor for global fault dete ction. the fault pin is forced active by any one o f the following fault scenarios: ? the v oltage at i out _x attempts to rise above the compliance range due to an open - loop circuit or insufficient power supply voltage. the internal circuitry that develops the fault output avoids using a comparator with window ed limits because this require s an actual output error before the fault output becomes active. instead, the signal is generated when the internal amplifier in the output stage has less than approximately 1 v of remaining drive capability. thus , the fault output activates slightly before the compliance limit is reached. ? a short is detected on a voltage output pin. the s hort - circuit current is limited to 16 ma or 8 ma, which is programmable by the user. if using the ad5755 - 1 in unipolar supply mode, a short - circuit fault may be generated if the output voltage is below 50 m v. ? an interface error is detected due to a pec failure. see the packet error checking section. ? if the core temperature of the ad5755 -1 exceeds approximately 150c. the v out_ x f ault , i out_ x f ault , pec error , and over temp bits of the s tatus r egister are used in conjunction with the fault output to inform the user which one of the fault conditions caused the fault output to be activated. voltage output short - circuit protection under normal operation , the voltage output sink s /source s up to 1 2 ma and maintain s specified operation. t he maximum output current or short - circuit current is programmable by the user and can be set to 1 6 ma or 8 ma. if a short circ uit is detected , the fault go es low and the relevant v out_x fault bit in the s tatus register is set. digital offset and gain cont rol each dac channel has a gain (m) and offset (c) register, which allow trimming out of the gain and offset errors of the entire signal chain. data from the dac d ata r egister is operated on by a digital multiplier and adder controlled by the contents of the m and c registers. the calibrated dac data is then stored in the dac input register. 09226-075 dac input register dac dac d at a register m register c register figure 77 . digital offset and gain control although figure 77 indicates a multiplier and adde r for each channel, there is only one multiplier and one adder in the device, and they are shared among all four channels. this has implications for the update speed when several channels are updated at once ( see table 3 ). each t ime data is written to the m or c register , the output is not automatically updated. instead , the next write to the dac channel use s these m and c values to perform a new calibration and automatically update s the channel. the output data from the calibra tion is routed to the dac input register. this is then loaded to the dac as described in the theory of operation section. both the gain r egister and the o ffset r egister have 16 bits of resolution. the correct method to calibrate t he gain/offset is to first calibrate out the gain and then calibrate the offset. the value (in decimal) that is written to the dac input register can be calculated by 15 16 2 2 )1( ?+ + = c m d code r dacregiste (1) where: d is the code loaded to the dac channel s input registe r. m is the code in the g ain register ( default code = 2 16 C 1 ). c is the code in the o ffset register ( default code = 2 15 ). status readback duri ng a write the ad5755 -1 has the ability to read back the s tatus register contents during every write sequence. this feature is enabled via the statread bit in the m ain c ontrol r egister. this allows the user to continuously monitor the s tatus r egister and act quickly in the case of a fault. when s tatus r eadback d uring a w rite is enabled , the contents of the 16 - bit s ta tus register ( s ee table 30) are output on the sdo pin , as shown in figure 5 . the ad5755 -1 power s up with this feature disabled. when this is enabled , the normal readback feature is not available, except for the status register. to read back any other register , clear the statread bit first before following the readback sequence. statread can be set high again after the register read.
data sheet AD5755-1 rev. e | page 41 of 52 asynchronous clear clear is an active high , edge - sensitive input that a llows th e output to be cleared to a pre pro grammed 16 - bit code. this code is user programmable via a per channel 16 - bit c lear c ode register. f or a channel to clear, that channel must be enabled to be cleared via the clr_en bit in the channel s dac c ontrol r egister. if the channel is not enabled to be cleared , then the output remain s in its current state independent of the clear pin level. when the clear signal is returned low, the relevant outputs remain cleared until a new value is programmed. packet erro r checking to verify that data has been received correctly in noisy environ - ments, the ad5755 -1 offers the option of packet error checking based on an 8 - bit cyclic redundancy check (crc - 8) . the device controlling the ad5755 -1 should generate an 8- bit fram e check sequence using the polynomial c ( x ) = x 8 + x 2 + x 1 + 1 this is added to the end of the data - word, and 32 bits are sent to the ad5755 -1 before taking sync high. if the ad5755 -1 sees a 32- bit frame, it perform s the error check w hen sync goes high. if the check is valid, the data is written to the selected register. if the error check fails, the fault pin go es low and the pec error bit in the s tatus register is set. after reading the s tatu s register, fault return s high (assuming there are no other faults), and the pec error bit is cleared automatically. it is not recommended to tie both ad1 and ad0 low as a short low on sdin could possibly lead to a zero - scale update for d ac a. sdin sync sclk update on sync high msb d23 lsb d0 24-bit data 24-bit data transfer?no error checking sdin fault sync sclk update on sync high only if error check passed fault pin goes low if error check fails msb d31 lsb d8 d7 d0 24-bit data 8-bit crc 32-bit data transfer with error checking 09226-180 figure 78 . pec timing the pec can be used for both transmit and receive of data packets. if s tatus r eadback d uring a w rite is enabled, the pec values returned during the s tatus r eadback d uring a w rite operation should be ig nored. if s tatus r eadback d uring a w rite is disabled, th e user can still use the normal readback operation to monitor s tatus r egister activity with pec . watchdog t imer when enabled, an on - chip watchdog timer generate s an alert signal if 0x195 has not been written to the s oftware register within the programmed timeout period. this feature is useful to ensure that communication has not been lost between the mcu and the ad5755 -1 and that these datapath lines are working properly ( that is, sdi n, sclk , and sync ). if 0x195 is not received by the s oftware r egister within the timeout period, the alert pin signal s a fault condition. the alert signal is active high and can be connected directly to the clear pin to enable a clear in the event tha t communication from the mcu is lost . the watchdog timer is enabled , and the timeout period (5 ms , 10 ms , 10 0 ms, or 200 ms) is set in the main control register ( s ee table 18 and table 19). output alert the ad5755 -1 is equipped with a n alert pin . this is a n active high cmos output. the ad5755 -1 also has an internal watchdog timer. when enabled, it monitor s spi communica - tions. if 0x195 is not received by the s oftware r egister within the timeout period, th e alert pin go es active. internal reference the ad5755 -1 contains an integrated +5 v voltage reference with initial accuracy of 5 mv max imum and a temperature drift coefficient of 10 ppm max imum . the reference voltage is buffered and externally available for use elsewhere within the system. refout must be connected to refin to use the internal reference. external c urrent s etting r esistor referring to figure 73, r set is an internal sense resistor as part of th e voltage - to - curre nt conversion circuitry. the stability of the output current value over temperature is dependent on the stability of the value of r set . as a method of improving the stability of the output current over temperature , an external 15 k? low drift resistor can be connected to the r set _x pin of the ad5755 -1 to be used instead of the internal resistor , r1. the external resistor is selected via the dac c ontrol register (s ee table 20 ). table 1 outlines the performa nce specifications of the ad5 755 -1 with both the internal r set resistor and an external, 15 k? r set resistor. using an external r set resistor allows for improved performance over the internal r set resistor option . the external r set resistor specification assumes an ideal resistor; the actual performance depends on the absolute value and temperat ure coefficient of the resistor used. this directly affect s the gain error of the output, and thus the total unadjusted error. to arrive at the gain /tue error of the output with a particular external r set resistor, add the percentage absolute error of the r set resistor
AD5755-1 data sheet rev. e | page 42 of 52 directly to the gain /tue error of the ad5755 - 1 with the exter - nal r set resistor, shown in table 1 (expressed in % fsr) . hart the ad5755 -1 has four chart pins, one corresponding to each output channels. a hart signal can be coupled into these pins. the hart signal appear s on the corresponding current output, if the output is enable d . table 31 shows the recommended input voltages for the hart signal at the chart pin. if these voltages are used , the current output should meet the hart amplitude specifications. figure 79 shows the recommended circuit for attenuating and coupling in the hart signal. table 31 . chart input voltage to hart output curr ent r set chart input voltage current output (hart) internal r set 150 mv p-p 1 ma p-p external r set 170 mv p-p 1 ma p-p 09226-076 hart modem output c1 c2 chartx figure 79 . coupling hart signal a minimum capacitance of c1 + c2 is required to ensure that the 1.2 khz and 2.2 khz hart frequencie s are not significantly attenuated at the output. the recommended values are c1 = 22 n f, c 2 = 47 n f. digitally controlling the slew rate of the output is necessary to meet the analog rate of change requirements for hart. dig ital sle w r ate control the s lew r ate c ontrol feature of the ad5755 -1 allows the user to control the rate at which the output value changes. this feature is available on both the current and voltage outputs. with the slew rate control feature disabled , the output value change s at a rate limited by the output drive circuitry and the attached load. to reduce the slew rate , this can be achieved by enabling the slew rate control feature. with the feature enabled via the sren bit of the s lew r ate c ontrol register (s ee table 26 ), the output, instead of slewing directly between two values, step s digitally at a rate defined by two parameters accessible via the s lew r ate c ontrol register, as shown in table 26 . the parameter s are sr_clock and sr_step. sr_clock defines the rate at which the digital slew is updated, for example, if the selected update rate is 8 k hz , the output update s every 125 s . in conjunc tion with this , sr_step defines by how much the output value change s at each update. together , both parameters define the rate of change of the output value. table 32 and table 33 outline the range of values for both the sr_clock and sr_step parameters. table 32 . slew rate update clock options sr_clock update clock fr equency (hz) 1 0000 64 k 0001 32 k 0010 16 k 0011 8 k 0100 4 k 0101 2 k 0110 1 k 0111 500 1000 250 1001 125 1010 64 1011 32 1100 16 1101 8 1110 4 1111 0.5 1 these cl ock frequencies are divided down from the 13 mhz internal oscillator. see table 1 , figure 69 , and figure 70 . table 33 . slew rate step size options sr_step step size (lsbs) 000 1 001 2 010 4 011 16 100 32 101 64 110 128 111 256 the following equation describes the slew rate as a function of the step size, the update clock frequency , and the lsb size: size lsb frequency clock update size step change output time slew = w here: slew time is expres sed in seconds . output change is expressed in a mps for i out _x or v olts for v o ut _x . when the slew rate control feature is enabled, all output changes occur at the programmed slew rate (see the dc - to - dc converter settling time secti on for additional information ) . for example , if the clear pin is asserted , the output slew s to the clear value at the programmed slew rate (assuming that the c lear channel is enabled to be cleared). if a number of channels are enabled for slew, care must b e taken when asserting the clear pin . if one of the channels is slewing when clear is asserted , other chan - nels may change directly to their clear value s not under slew rate control . the update clock frequency for any given value is the same for all output ranges . the step size , however , var ies across output ranges for a given value of step size because the lsb size is different for each output range.
data sheet AD5755-1 rev. e | page 43 of 52 power dissipation co ntrol the ad5755 -1 contains integrated dynamic power control using a dc - to - dc boost con verter circuit , allowing reductions in power consumption from standard designs when using the part in current output mode. in standard current input module designs , the load resistor values can range from typically 50 ? to 750 ? . output module systems mus t source enough voltage to meet the compliance voltage requirement across the full range of load resistor values. for example, in a 4 ma to 20 ma loop when driving 20 m a, a compliance voltage of >15 v is required. when driving 20 ma into a 50 ? load , only 1 v compliance is required. the ad5755 -1 circuitry senses the output voltage and regulates this voltage to meet compliance requirements plus a small headroom voltage. the ad5755 -1 is capable of driving up to 24 ma through a 1 k? load. dc- to - dc converters the ad5755 -1 contains four independent dc - to - dc converters. these are used to provide dynamic control of the v boost supply voltage for each channel ( s ee figure 73 ). figure 80 shows the discret e component s needed for the dc - to - dc circuitry , and the following sections describe component selection and operation of this circuitry. av cc l dcdc d dcdc c dcdc 4.7f c filter 0.1f r filter c in swx v boost_x 10f 10? 10h 09226-077 figure 80 . dc -to- dc circuit table 34 . recommended dc -to - dc components symbol co mponent value manufacturer l dcdc xal4040 - 103 10 h coil c raft ? c dcdc grm32er71h475ka88l 4.7 f murata d dcdc pmeg3010bea 0.38 v f nxp it is recommended to place a 10 ?, 100 nf low - pass rc filter after c dcdc . this consume s a small amount of power but reduc es the amount of ripple on the v boost _x supply. dc - to - dc converter operation the on - board dc - to - dc converters use a constant frequency, peak curr ent mode control scheme to step up an av cc input of 4.5 v to 5.5 v to drive the ad5755 -1 output channel. these are designed to operate in discontinuous conduction mode (dcm) with a duty cycle of < 90 % typical . discontinuous cond uction mode refers to a mode of operation where the inductor current goes to zero for an appreciable percentage of the switching cycle. the dc - to - dc converters are nonsynchronous ; that is, they requ ire an external schottky diode. dc - to - dc converter output voltage when a channel current output is enabled , the converter regu lates the v boost _x su pply to 7.4 v (5%) or (i out r load + headroom) , w hichever is greater (see figure 53 for a plot of headroom supplied vs . output current ). in voltage output mode with the output disabled, the converter regulates the v boost _x supply to +15 v ( 5%). in current output mode with the o utput disabled, the converter regulates the v boost_x supply to 7.4 v (5%). within a channel , the v out _x and i out _x stages share a common v boost _x supply s o that the outputs of the i out _x and v out _x stages can be tied together. dc - to - dc converter settling time when in current output mode, the settling time for a step greater than ~1 v (i out r load ) is dominated by the settling time of the dc - to - dc converter. the exception to this is when the required voltage at the i out_ x pin plus the compliance voltage is below 7.4 v (5%). a typical plot of the output settling time can be found in figure 49 . this plot is for a 1 k? load. the settling time for smaller loads is faster. the settling time for current steps less than 24 ma is also fas ter. dc - to - dc converter v max functionality the maximum v boost _x voltage is set in the dc - to - dc c ontrol r egister ( 23 v, 2 4.5 v, 27 v, or 29.5 v; s ee table 25 ). on reaching this maximum voltage , the dc - to - dc converter is disabled, a nd the v boost _x voltage is allowed to decay by ~0.4 v. after the v boost _x voltage has decayed by ~0.4 v , the dc - to - dc converter is re enabled , and the voltage ramp s up again to v max , if still required. this operation is shown in fi g ure 81 . 28.6 28.7 28.8 28.9 29.0 29.1 29.2 29.3 29.4 29.5 29.6 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 v boost vo lt age (v) time (ms) v max 0ma to 24ma range, 24ma output output unloaded dc-dcmaxv = 11 (29.5v) dc_dc bit 09226-183 dcdcx bit = 0 dcdcx bit = 1 f sw = 410khz t a = 25c figure 81 . operation on reaching v max as can be seen in figure 81 , the dc - dcx bit in the status register asserts when the ad5755 - 1 is ramping to the v max value but deasserts when the voltage i s decaying to v max ? ~0.4 v . dc - to - dc converter on - board switch the ad5755 -1 contains a 0.4 25 ? internal switch . the switch current is monit ored on a pulse by pulse basis and is limited to 0.8 a peak current. dc - to - dc converter switching frequency and phase the ad5755 -1 dc -to- dc converter switching frequency can be selected from the dc - to - dc c ontro l register. the phasing of the channels can also be adjusted so that the dc - to - dc converter can clock on different edges ( s ee table 25 ). for typical applic ations , a 410 kh z frequency is recommended. at light loads (low output
AD5755-1 data sheet rev. e | page 44 of 52 current and small load resistor) , the dc - to - dc converter enters a pulse - skipping mode to minimize switching power dissipation. dc - to - dc converter inductor selection for typical 4 ma to 20 ma applications , a 10 h inductor (such as the xal4040 - 103 from coilcraft) , combined with a switch - ing frequency of 410 kh z, allow s up to 24 ma to be driven into a load resistance of up to 1 k? with an av cc supply of 4.5 v to 5.5 v. it is important to e nsure that the inductor is able to handle the peak current without saturating , especially at the maximum ambient temperature. if the inductor enter s into saturation mode , it res ult s in a decrease in efficiency. the inductance value also drop s during satura tion and may result in the dc - to - dc converter circuit not being able to supply the required output power. dc - to - dc converter external schottky selection the ad5755 -1 requires an external schottky for correct operation. ensure that the schottky is rated to handle the maximum reverse breakdown expected in operation and that the rectifier maximum junction temperature is not exceeded. the diode average current is approximately equal to the i load current. diodes with larger forward voltage drops result in a decr ease in efficiency. dc - to - dc converter compensation capacitors as the dc - to - dc converter operates in dcm , the uncompensated transfer f unction is essentially a single - pole transfer function. the pole frequency of the transfer function is determined by the d c- to - dc converter s output capacitance, input and output voltage , and output load. the ad5755 -1 uses an external capacitor in conjunction with an internal 150 k? resistor to compensate the regulator loop. alternatively , an external compensation resistor ca n be used in series with the compensation capacitor, by setting the dc - dc comp bit in the dc - to - dc c ontrol r egister. in this case , a ~50 k? resistor is recommended . a description of the advantages of this can be found in the ai cc s upply requirements slewing section. for typical applications , a 10 nf dc - to - dc compensation capacitor is recommended. dc - to - dc converter input and output capacitor selection the output capacitor a ffects ripple voltage of the dc - to - dc converter and indirec tly limits the maximum slew rate at which the channel output current can rise. the ripple voltage is caused by a com bination of the capacitance and equivalent series resistance ( esr ) of the capacitor. for the ad5755 -1, a ceramic capacitor of 4.7 f is reco mmended for typical applications. larger capacitors or paral lel ed capacitors improve the ripple at t he expense of reduced slew rate . larger capacitors also impact the av cc supplies current requirements while slewing (see the ai cc s upply requirements slewing section). this capaci t ance at the output of the dc - to - dc converter should be > 3 f under all operating conditions. the input capacitor provide s much of the dynamic current required for the dc - to - dc converter and should be a low esr component. for the ad5755 -1, a low esr tantalum or ceramic capacitor of 10 f is recommended for typical applications. ceramic capacitors must be chosen carefully because they can exhibit a large sensitivity to dc bias voltages and temperature. x5r or x7r dielectrics are preferred because these capacitors remain stable over wider operating voltage and temperature ranges. care must be taken if selecting a tantalum capacitor to ensure a low esr value. ai cc supply requirements static the dc - to - dc converte r is designed to supply a v boost _x voltage of v boost = i out r load + headroom (2) see figure 53 for a plot of headroom supplied vs . output voltage . this means that, for a fixed load and output voltage , the dc - to - dc converter ou tput current can be calculated by the following formula: cc v boost out cc cc av vi av efficiency out power ai boost = = (3) w here: i out is the output current from i out_ x in amps. v boost is the efficiency at v boost _x as a fraction (see figure 55 and figure 56 ). ai cc supply requirements s lewing the ai cc current requirement while slewing is greater than in static operation because t he output power increases to charge the output capacitance of the dc - to - dc converter. this transient current can be quite large (see figure 82 ), al though the methods described in the reducing ai cc current requirements section can reduce the requirements on the av cc supply. if not enough ai cc current can be provided, the av cc voltage dr op s . due to this av cc dr op , the ai cc current required to slew increase s further. this means that the voltage at av cc drop s further (see equation 3) and the v boost _x voltage , and thus the output voltage , may never reach its intended value. because this av cc voltage is common to all channels, this may also affect other channels. 0 5 10 15 20 25 30 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 0. 5 1.0 1.5 2.0 2.5 i out_x current (ma )/ v boost_x vo lt age (v) ai cc current (a) time (ms) ai cc i out v boost 0ma to 24ma range n?/2$' f sw = 410khz inductor = 10h (xal4040-103) t a = 25c 09226-184 figure 82 . ai cc current vs. time for 24 ma step through 1 k load with internal compensation resistor
data sheet AD5755-1 rev. e | page 45 of 52 reducing ai cc current requirements there are two main methods that can be used to reduce the ai cc current requirements. one method is to add an external compensation resistor , and the other is to use slew rate control. both of these methods can be used in conjunction. a compensation resistor can be placed at the comp dcdc_ x pin in series with the 10 nf compensation capacitor. a 51 k? exter - nal compensation resistor is recommended. this compensation incr ease s the slew time of the current output but ease s the ai cc transient current requirements. figure 83 shows a plot of ai cc current for a 24 ma step through a 1 k? load when using a 51 k? compensation resistor. this method ease s t he current requirements through smaller loads even further, as shown in figure 84. 0 4 12 8 16 24 20 28 32 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 ai cc current (a) 0ma to 24ma range 1k? load f sw = 410khz inductor = 10h (xal4040-103) t a = 25c 09226-185 0 0.5 1.0 1.5 2.0 2.5 i out_x current (ma )/ v boost_x vo lt age (v) time (ms) ai cc i out v boost figure 83 . ai cc current vs. time for 24 ma step through 1 k? load with external 51 k? compensation resistor 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 ai cc current (a) 0ma to 24ma range 500? load f sw = 410khz inductor = 10h (xal4040-103) t a = 25c 09226-186 0 4 12 8 16 24 20 28 32 0 0.5 1.0 1.5 2.0 2.5 i out_x current (ma )/ v boost_x vo lt age (v) time (ms) ai cc i out v boost figure 84 . ai cc current vs. time for 24 ma step through 500 ? load with external 51 k? compensation resistor using slew rate control can greatly reduce the av cc supplies current requirements, as shown in figure 85 . when using slew rate control , attention should be paid to the fact that the output cannot slew faster than the dc - to - dc converter. the dc - to - dc converter slew s slowest at higher currents through large ( for example, 1 k?) loads. this slew rate is also dep endent on the configuration of the dc - to - dc converter . two examples of the dc - to - dc converter output slew are shown in figure 83 and figure 84 (v boost corresponds to the dc - to - dc converter s output voltag e). 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 ai cc current (a) 0ma to 24ma range 1k? load f sw = 410khz inductor = 10h (xal4040-103) t a = 25c 0 4 12 8 16 24 20 28 32 09226-187 0 1 2 3 4 5 6 i out_x current (ma )/ v boost_x vo lt age (v) time (ms) ai cc i out v boost figure 85 . ai cc current vs. time for 24 ma step through 1 k? load with slew rate control
AD5755-1 data sheet rev. e | page 46 of 52 applications informa tion voltage and current o utput ranges on the same terminal when using a channel of the ad5755 - 1, the current and voltage output pins can be connected to two s eparate terminals or tied together and connected to a single terminal. there is no conflict with tying the two output pins together because only the voltage output or the current output can be enabled at any one time. when the current output is enabled , th e voltage output is in tristate mode, and when the voltage output is enabled , the current output is in tristate mode. for this operation, the poc pin must be tied low and the poc bit in the main control register set to 0 , or, if the poc pin is tied high , t he poc bit in the main control register must be set to 1 before the current output is enabled. as shown in the absolute maximum ratings section, the output tolerances are the same for both the voltage and current output pins. the +v sense _x connections are buffered so that current leakage into these pins is negligible when in current output mode. current output mode w ith internal r set when using the internal r set resistor in current output mode , the output is significantly affected by how many other channels using the internal r set are enabled and by the dc crosstalk from these channels. the internal r set specifications in table 1 are for all channels enabled with the internal r set selected and outputting the same code. for every channel enabled with the internal r set , the offset error decreases. for example, with one current output enabled using the internal r set , the offset error is 0.075% fsr. this value decreases proportionally as more current channels are enabled; the offset error is 0.056% fsr on each of two channels, 0.029% on each of three channels, and 0.01% on each of four channels. similarly, the dc crosstalk when using the internal r set is propor - tional to the number of current output channels e nabled with the internal r set . for example, with the measured channel at 0x8000 and one channel going from zero to full scale, the dc crosstalk is ?0.011% fsr. with two channels going from zero to full scale, it is ?0.019% fsr, and with all three other channels going from zero to full scale, it is ?0.025% fsr. for the full - scale error measurement in table 1 , all channels are at 0xffff. this means that, as any channel goes to zero scale, the full - scale error increase s due to the dc crosstalk. for example , with the measured channel at 0xffff and three channels at zero scale, the full - scale error is 0.025%. similarly , if only one channel is enabled in current output mode with the internal r set , the full - scale error is 0.025% fsr + 0.075% fsr = 0.1% fsr. precision voltage reference se lection to achieve the optimum performance from the ad5755 -1 over its full operating temperature range, a precision voltage reference must be used. thought should be given to the selection of a precision voltage reference. the voltage applied to the reference inputs is used to provide a buffered reference for the dac cores. therefore, any error in the voltage reference is reflected in the outputs of the device. there are four possible sources of error to consider when choosing a voltage reference for high accuracy applications: initial accuracy, temperature coefficient of the output voltage, long term drift, and output voltage noise. initial accuracy error on the output voltage of an external refer - ence can lead to a full - scale error in the dac. therefore, to minimize these errors, a reference with low initial accuracy error specification is preferred. choosing a reference with an output trim adjustment, such as the adr425, allows a system designer to trim system errors out by setting the reference voltage to a voltage other than the nominal. the trim adjust - ment can be used at any temperature to trim out any error. long - term drift is a measure of how much the reference output voltage drifts over time. a reference with a tight long - term dr ift specification ensures that the overall solution remains relatively stable over its entire lifetime. the temperature coefficient of a references output voltage affects inl, dnl, and tue. a reference with a tight temperature coefficient specification sh ould be chosen to reduce the depend - e nce of the dac output voltage to ambient temperature . in high accuracy applications, which have a relatively low noise budget, reference output voltage noise must be considered. choosing a reference with as low an outpu t noise voltage as practical for the system resolution required is important. precision voltage references such as the adr435 (xfet design) produce low output noise in the 0.1 hz to 10 hz region. however, as th e circuit bandwidth increases, filtering the output of the reference may be required to minimize the output noise. table 35 . recommended precision references part no. initial accuracy (mv maximum) long - term drift (ppm typical) te mperature drift (ppm/c maximum) 0.1 hz to 10 hz noise (v p - p typical) adr445 2 50 3 2.25 adr02 3 50 3 10 adr435 2 40 3 8 adr395 5 50 9 8 ad586 2.5 15 10 4
data sheet AD5755-1 rev. e | page 47 of 52 driving inductive lo ads when driving inductive or poorly defined loads, a capacitor may be required between i out_ x and agnd to ensure stability. a 0.01 f capacitor between i out_x and agnd ensures stability of a load of 50 mh. the capacitive component of the load may cause slower settling, although this may be masked by the set - tling time of the ad5755 - 1. there is n o maximum capacitance limit for the current output of the ad5755 - 1. transient voltage pr otection the ad5755 -1 contains esd protection diodes that prevent dam age from normal handling. the industrial control environment can, however, subject i/o circuits to much higher transients. to protect the ad5755 -1 from excessively high voltage transients, external power diodes and a surge current limiting resistor (r p ) are required, as shown in figure 86 . a typical value for r p is 10 ?. the two protection diodes and the resistor (r p ) must have appro priate power ratings. r load r p d2 d1 av ss AD5755-1 v boost_x i out_x agnd 09226-079 r fi l ter c fi l ter 0.1f 10? (from dc- t o-dc converter) c dcdc 4.7f figure 86 . output transient voltage protection further protection can be provided using transient voltage suppressors (tvss), also referred to as transorbs. these compo - nents are available as unidirectional suppressors, which protect against positive high voltage transients, and as bidirectional suppressors, which protect against both positive and negative high voltage transients. transient voltage s uppressors are avail - able in a wide range of standoff and breakdown voltage ratings. the tvs should be sized with the lowest breakdown voltage possible while not conducting in the functional range of the current output. it is recommended that all field con nected nodes be protected. the voltage output node can be protected with a similar circuit, where d2 and the transorb are connected to av ss . for the volt - age output node, the +v sense_x pin should also be protected with a large value series resistance to th e transorb, such as 5 k?. in this way, the i out_x and v out_x pins can also be tied together and share the same protection circuitry. microprocessor inter facing microprocessor interfacing to the ad5755 -1 is via a serial bus that uses a protocol compatible with microcontrollers and dsp processors. the communications channel is a 3 - wire minimum interface consisting of a clock signal, a data signal, and a latch signal. the ad5755 -1 require s a 24 - bit data - word with data valid on the falling edge of sclk. the da c output update is initiated on either the rising edge of ldac or, if ldac is held low, on the rising edge of sync . the contents of the registers can be read using the readback function. ad5755 -1- to - adsp - bf527 interface the ad5755 -1 can be connected directly to the sport interface of the adsp - bf527, an analog devices, inc., blackfin? dsp. figure 87 shows how the sport interface can be connected to control the ad 5755 -1. 09226-080 AD5755-1 sync sclk sdin ldac sport_tfs sport_tsck sport_d to gpio0 adsp-bf527 figure 87 . ad5755 -1-to- adsp - bf527 sport interface layout guidelines grounding in any circuit where accuracy is important, careful consideration of the power supply and ground return layout helps to ensure the rated perfor mance. the printed circuit board on which the ad5755 -1 is mounted should be designed so that the analog and digital sections are separated and confined to certain areas of the board. if the ad5755 -1 is in a system where multiple devices require an agnd - to - dgnd connection, the connection should be made at one point only. the star ground point should be established as close as possible to the device. the gndsw x and ground connection for the av cc supply are referred to as pgnd. pgnd should be confined to certa in areas of the board, and the p gnd - to - agnd connection should be made at one point only. supply dec oupling the ad5755 -1 should have ample supply bypassing of 10 f in parallel with 0.1 f on each supply located as close to the package as possible, ideally right up against the device. the 10 f capacitors are the tantalum bead type. the 0.1 f capacitor should have low effective series resistance (esr) and low effective series inductance (esl ), such as the common ceramic types, which provide a low impedance path to ground at high frequencies to handle transient currents due to internal logic switching.
AD5755-1 data sheet rev. e | page 48 of 52 traces the power supply lines of the ad5755 -1 should use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on t he power supply line. fast switching signals such as clocks should be shielded with digital ground to prevent radiating noise to other parts of the board and should never be run near the reference inputs. a ground line routed between the sdin and sclk lin es helps reduce crosstalk between them (not required on a multilayer board that has a separate ground plane, but separating the lines helps). it is essential to minimize noise on the refin line because it couples through to the dac output. avoid crossover of digital and analog signals. traces on oppo - site sides of the board should run at right angles to each other. this reduces the effects of feedthrough on the board. a microstrip technique is by far the best but not always possible with a double - sided boar d. in this technique, the component side of the board is dedicated to ground plane, whereas signal traces are placed on the solder side. dc - to - dc converters to achieve high efficiency, good regulation, and stability, a well - designed printed circuit board l ayout is required. follow these guidelines when designing printed circuit boards (s ee figure 80 ): ? keep the low esr input capacitor, c in , close to av cc and p gnd. ? keep the high current path from c in through the inductor, l dcdc , to sw x and pgnd as short as possible. ? keep the high current path from c in through l dcdc and the rectifier, d dcdc , to the output capacitor, c dcdc , as short as possible. ? keep high current traces as short and as wide as possible. the path from c in through the inductor, l dcdc , to sw x and pgnd should be able to handle a minimum of 1 a. ? place the compensation components as close as possible to comp dcdc _x . ? avoid routing high impedance traces near any node connected to sw x or near the inductor to prevent radiated noise injection. galvanically isolate d interface in many process control applications, it is necessary to provide an isolation barrier between the controller and the unit being controlled to protect and isolate the controlling circuitry from any hazardous common - mode voltages that may occ ur. the analog devices i coupler? products can provide voltage isolation in excess of 2.5 kv. the serial loading structure of the ad5755 - 1 makes it ideal for isolated interfaces because the number of interface lines is kept to a minimum. figure 88 shows a 4 - channel isolated interface to the ad5755 -1 using an adum1400 . for more information, visit www.analog.com . 09226-081 v ia serial clock out to sclk v oa encode decode v ib serial data out to sdin v ob encode decode v ic sync out v oc encode decode v id control out v od encode decode microcontroller adum1400* *additional pins omitted for clarity. to sync to ldac f igure 88 . isolated interface
data sheet AD5755-1 rev. e | page 49 of 52 industrial hart c apable analog output application s hared v out _x and i out _x p in many industrial control applications have requirements for accurately controlled current output signals, and the ad5755 - 1 is ideal for such applications. figure 89 shows the ad5755 - 1 in a circuit design for a hart - enabled output module, specifically for use in an industrial control application in which both the voltage output and current output are available one at a time on one pin, thus reducing the number of screw connections required. there is no conflict with tying the two output pins together because only the voltage output or the current output can be enabled at any one time. the design prov ides for a hart - enabled current output, with the hart capability provided by the ad5700/ad5700 - 1 hart m odem, the industrys lowest power and smallest footprint hart - compliant ic modem. for additional space - savings, the ad5700 -1 offers a 0.5% precision internal oscillator. the hart_out signal from the ad5700 is attenuated and ac - coupled into the chart x pin of the ad5755 - 1. such a configuration results in the ad5700 hart modem output modulating the 4 ma to 20 ma analog current without affecting the dc level o f the current. this circuit adheres to the hart physical layer specifications as defined by the hart communication foundation. for transient overvoltage protection, a 24 v transient voltage suppressor (tvs) is placed on the i out /v out connection. for added protection, clamping diodes are connected from the i out _x /v out _x pin to the av dd and av ss power supply pins. a 5 k current limiting resistor is also placed in series with the +v sense_ x input. this is to limit the current to an acceptable level during a transient event. the recommended external band - pass filter for the ad5700 hart modem includes a 150 k resistor, whi ch limits current to a sufficiently low level to adhere to intrinsic safety requirements. in this case, the input has higher transient voltage protection and should, therefore, not require additional protection circuitry, even in the most demanding of indu strial environments. hart_out gnd txd rxd rts cd vcc ad5700/ad5700-1 0.1f adc_ip ref gnd refin reset av dd sw (4) v boost (4) chart a AD5755-1 dv dd +15v +5v 10k? 0.1f 0.1f 0.1f 10f 10f 2.7v to 5.5v 1.2m? 1.2m? 150k? 300pf 150pf 1f mcu d1 d2 r l 500? r p vouta +vsense_a d3 av ss av ss uart interface av cc iout b, c, d iout a chart b, c, d vout b, c, d refout dgnd ldac sdo sdin sclk sync clear fault alert 47nf c2 22nf c1 5k? 4ma to 20ma current loop 09226-089 figure 89 . ad5755 - 1 in hart configuration
AD5755-1 data sheet rev. e | page 50 of 52 outline dimensions compliant to jedec standards mo-220-vmmd-4 0.25 min 1 64 16 17 49 48 32 33 0.50 0.40 0.30 0.50 bsc 0.20 ref 12 max 0.80 max 0.65 typ 1.00 0.85 0.80 7.50 ref 0.05 max 0.02 nom 0.60 max 0.60 max seating plane pin 1 indicator 7.25 7.10 sq 6.95 pin 1 indicator 0.30 0.23 0.18 for proper connection of the exposed pad, refer to the pin configuration and function descriptions section of this data sheet. top view exposed pad bottom view 9.10 9.00 sq 8.90 8.85 8.75 sq 8.65 06-13-2012-c figure 90. 64- lead lead frame chip scale package [lfcsp_vq] 9 mm 9 mm body, very thin quad (cp-64-3) dimensions shown in millimeters ordering guide model 1 resolution (bits) temperature range pa ckage description package option AD5755-1acpz 16 ?40c to +105c 64-lead lfcsp_vq cp-64-3 AD5755-1acpz-reel7 16 ?40c to +105c 64-lead lfcsp_vq cp-64-3 eval-AD5755-1sdz evaluation board 1 z = rohs compliant part.
data sheet AD5755-1 rev. e | page 51 of 52 notes
AD5755-1 data sheet rev. e | page 52 of 52 notes ? 2011 C 2012 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d09226 -0- 11/12(e)

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