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complete dual, 16-bit, high accuracy, serial input, bipolar voltage output dacs preliminary technical data ad5762r rev. pra 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 www.analog.com fax: 781.461.3113 ?2007 analog devices, inc. all rights reserved. features complete dual, 16-bit digital-to-analog converters (dacs) programmable output range: 10 v, 10.2564 v, or 10.5263 v 1 lsb max inl error, 1 lsb max dnl error low noise: 60 nv/hz settling time: 10 s max integrated reference buffers internal reference: 10 ppm/c on-chip die temperature sensor output control during power-up/brownout programmable short-circuit protection simultaneous updating via ldac asynchronous clr to zero code digital offset and gain adjust logic output control pins dsp-/microcontroller-compatible serial interface temperature range: ?40c to +85c i cmos? process technology 1 applications industrial automation open-/closed-loop servo control process control data acquisition systems automatic test equipment automotive test and measurement high accuracy instrumentation general description the ad5762r is a dual, 16-bit, serial input, bipolar voltage output digital-to-analog converter that operates from supply voltages of 11.4 v up to 16.5 v. nominal full-scale output range is 10 v. the ad5762r provides integrated output amplifiers, reference buffers and proprietary power-up/power- down control circuitry. the parts also feature a digital i/o port, which is programmed via the serial interface and an analog temperature sensor. the part incorporates digital offset and gain adjust registers per channel. the ad5762r is a high performance converter that offers guaranteed monotonicity, integral nonlinearity (inl) of 1 lsb, low noise, and 10 s settling time. the ad5762r includes an on-chip 5 v reference with a reference tempco of 10 ppm/c maximum. during power-up (when the supply voltages are changing), vout is clamped to 0 v via a low impedance path. the ad5762r uses a serial interface that operates at clock rates of up to 30 mhz and is compatible with dsp and microcontroller interface standards. double buffering allows the simultaneous updating of all dacs. the input coding is programmable to either twos complement or offset binary formats. the asynchronous clear function clears all dac registers to either bipolar zero or zero scale depending on the coding used. the ad5762r is ideal for both closed-loop servo control and open-loop control applications. the ad5762r is available in a 32-lead tqfp, and offers guaranteed specifications over the ?40c to +85c industrial temperature range. see figure 1, the functional block diagram. 1 for analog systems designers within industrial/instrumentation equipment oems who need high performance ics at higher voltage levels, i cmos is a technology platform that enables the development of analog ics capable of 30 v and operating at 15 v supplies wh ile allowing dramatic reductions in power consumption and package size, and increased ac and dc performance.
ad5762r preliminary technical data rev. pra | page 2 of 33 table of contents features .............................................................................................. 1 applications....................................................................................... 1 general description ......................................................................... 1 revision history ............................................................................... 2 functional block diagram .............................................................. 3 specifications..................................................................................... 4 ac performance characteristic...................................................... 6 timing characteristics..................................................................... 7 absolute maximum ratings.......................................................... 10 esd caution................................................................................ 10 pin configuration and function descriptions........................... 11 terminology .................................................................................... 13 typical performance characteristics ........................................... 15 theory of operation ...................................................................... 21 dac architecture....................................................................... 21 reference buffers........................................................................ 21 serial interface ............................................................................ 21 simultaneous updating via ldac ........................................... 22 transfer function ....................................................................... 23 asynchronous clear ( clr )....................................................... 23 function register ....................................................................... 24 data register............................................................................... 25 coarse gain register ................................................................. 25 fine gain register...................................................................... 25 offset register ............................................................................ 25 offset and gain adjustment worked example...................... 27 ad5762r features.......................................................................... 28 analog output control ............................................................. 28 digital offset and gain control............................................... 28 programmable short-circuit protection ................................ 28 digital i/o port........................................................................... 28 die temperature sensor............................................................. 28 local ground offset adjust...................................................... 28 applications information .............................................................. 29 typical operating circuit ......................................................... 29 layout guidelines........................................................................... 30 galvanically isolated interface ................................................. 30 microprocessor interfacing....................................................... 30 evaluation board ........................................................................ 32 outline dimensions ....................................................................... 33 ordering guide .......................................................................... 33 revision history preliminary revision pra december 10, 2007
preliminary technical data ad5762r rev. pra | page 3 of 33 functional block diagram input reg b gain reg b offset reg b dac reg b 16 dac b input reg a gain reg a offset reg a dac reg a 16 16 dac a ldac temp rstin rstout ref a refgnd agndb voutb agnda vouta iscc temp sensor reference buffers a v ss sdin sclk sync sdo d0 d1 bin/2scomp clr a v dd a v ss a v dd pgnd dv cc dgnd +5v reference voltage monitor and control input shift register and control logic g1 g2 g1 g2 refout ad5762r reference buffers refb figure 1. functional block diagram
ad5762r preliminary technical data rev. pra | page 4 of 33 specifications av dd = 11.4 v to 16.5 v, av ss = ?11.4 v to ?16.5 v, agnd = dgnd = refgnd = pgnd = 0 v; refa, refb = 5 v external; dv cc = 2.7 v to 5.25 v, r load = 10 k?, c l = 200 pf. all specifications t min to t max , unless otherwise noted. table 1. parameter c grade 2 unit test conditions/comments accuracy outputs unloaded resolution 16 bits relative accuracy (inl) 1 lsb max differential nonlinearity 1 lsb max guaranteed monotonic bipolar zero error 2 mv max at 25c; error at other temperatures obtained using bipolar zero tc bipolar zero tc 3 2 ppm fsr/c max zero-scale error 2 mv max at 25c; error at other temperatures obtained using zero scale tc zero-scale tc 3 2 ppm fsr/c max gain error 0.02 % fsr max at 25c; error at other temperatures obtained using gain tc gain tc 3 2 ppm fsr/c max dc crosstalk 3 0.5 lsb max reference input/output reference input 3 reference input voltage 5 v nominal 1% for specified performance dc input impedance 1 m? min typically 100 m? input current 10 a max typically 30 na reference range 1/7 v min/v max reference output output voltage 4.997/5.003 v min/v max at 25c reference tc 10 ppm/c max load 3 1 m ? min output noise 3 (0.1 hz to 10 hz) 18 v p-p typ noise spectral density 3 75 nv/hz typ at 10 khz output voltage drift vs. time 40 ppm/500hr typ output voltage drift vs. time 50 ppm/1000hr typ line regulation tbd ppm/v typ load regulation tbd ppm/ma typ thermal hysteresis tbd ppm typ output characteristics 3 output voltage range 4 10.5263 v min/v max av dd /av ss = 11.4 v, refa, refb = 5v 14 v min/v max av dd /av ss = 16.5 v, refa, refb = 7v output voltage drift vs. time 13 ppm fsr/500 hours typ 15 ppm fsr/1000 hours typ short circuit current 10 ma typ ri scc = 6 k?, see figure 31 load current 1 ma max for specified performance capacitive load stability r l = 200 pf max r l = 10 k? 1000 pf max dc output impedance 0.3 ? max
preliminary technical data ad5762r rev. pra | page 5 of 33 parameter c grade 2 unit test conditions/comments digital inputs 3 dv cc = 2.7 v to 5.25 v, jedec compliant v ih , input high voltage 2 v min v il , input low voltage 0.8 v max input current 1 a max per pin pin capacitance 10 pf max per pin digital outputs (d0, d1, sdo) 3 output low voltage 0.4 v max dv cc = 5 v 5%, sinking 200 a output high voltage dv cc ? 1 v min dv cc = 5 v 5%, sourcing 200 a output low voltage 0.4 v max dv cc = 2.7 v to 3.6 v, sinking 200 a output high voltage dv cc ? 0.5 v min dv cc = 2.7 v to 3.6 v, sourcing 200 a high impedance leakage current 1 a max sdo only high impedance output capacitance 5 pf typ sdo only die temperature sensor 3 output voltage at 25c 1.4 v typ die temperature output voltage scale factor 5 mv/c typ output voltage range 1.175/1.9 v min/v max ?40c to 105c output load current 200 a max current source only power-on time 80 ms typ power requirements av dd /av ss 11.4/16.5 v min/v max dv cc 2.7/5.25 v min/v max power supply sensitivity 3 ?v out /?v dd ?85 db typ ai dd 3.5 ma/channel max outputs unloaded ai ss 2.75 ma/channel max outputs unloaded di cc 1.2 ma max v ih = dv cc , v il = dgnd, 750 a typ power dissipation 140 mw typ 12 v operation output unloaded 2 temperature range : -40c to + 85c; typical at 25c. device functionality is guaranteed to +105c with degra ded performance. 3 guaranteed by design and characterization; not production tested. 4 output amplifier headroom requirement is 1.4 v minimum.
ad5762r preliminary technical data rev. pra | page 6 of 33 ac performance characteristic av dd = 11.4 v to 16.5 v, av ss = ?11.4 v to ?16.5 v, agnd = dgnd = refgnd = pgnd = 0 v; refa, refb= 5 v external; dv cc = 2.7 v to 5.25 v, r load = 10 k?, c l = 200 pf. all specifications t min to t max , unless otherwise noted. guaranteed by design and characterization, not production tested. table 2. parameter c grade unit test conditions/comments dynamic performance 1 output voltage settling time 8 s typ full-scale step to 1 lsb 10 s max 2 s typ 512 lsb step settling slew rate 5 v/s typ digital-to-analog glitch energy 8 nv-s typ glitch impulse peak amplitude 25 mv max channel-to-channel isolation 80 db typ dac-to-dac crosstalk 8 nv-s typ digital crosstalk 2 nv-s typ digital feedthrough 2 nv-s typ effect of input bus activity on dac outputs output noise (0.1 hz to 10 hz) 0.1 lsb p-p typ output noise (0.1 hz to 100 khz) 45 v rms max 1/f corner frequency 1 khz typ output noise spectral density 60 nv/hz typ measured at 10 khz complete system output noise spectral density 2 80 nv/hz typ measured at 10 khz 1 guaranteed by design and characterization; not production tested. 2 includes noise contributions from integrated reference buffers,16-bit dac and output amplifier.
preliminary technical data ad5762r rev. pra | page 7 of 33 timing characteristics av dd = 11.4 v to 16.5 v, av ss = ?11.4 v to ?16.5 v, agnd = dgnd = refgnd = pgnd = 0 v; refa, refb= 5 v external; dv cc = 2.7 v to 5.25 v, r load = 10 k?, c l = 200 pf. 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 4 13 ns min 24 th sclk falling edge to sync rising edge t 6 40 ns min minimum sync high time t 7 2 ns min data setup time t 8 5 ns min data hold time t 9 1.4 s min sync rising edge to ldac falling edge (all dacs updated) 400 ns 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 output response time t 12 10 s max dac output settling time t 13 10 ns min clr pulse width low t 14 2 s max clr pulse activation time t 15 5, 6 25 ns max sclk rising edge to sdo valid t 16 13 ns min sync rising edge to sclk falling edge t 17 2 s min sync rising edge to dac output response time (ldac = 0) t 18 170 ns min ldac falling edge to sync rising edge 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 cc ) and timed from a voltage level of 1.2 v. 3 see figure 2, figure 3, and figure 4. 4 standalone mode only. 5 measured with the load circuit of figure 5. 6 daisy-chain mode only.
ad5762r preliminary technical data rev. pra | page 8 of 33 06064-002 db23 sclk sync sdin ldac ldac = 0 clr 12 24 db0 t 1 vout vout vout 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 17 t 18 t 13 t 14 figure 2. serial interface timing diagram ldac sdo sdin sync sclk 24 48 db23 db0 db23 db0 db23 input word for dac n undefined input word for dac n?1 input word for dac n db0 t 1 t 2 t 3 t 4 t 6 t 7 t 8 t 15 t 16 t 5 t 10 t 9 figure 3. daisy chain timing diagram
preliminary technical data ad5762r rev. pra | page 9 of 33 sdo sdin s yn c sclk 24 48 db23 db0 db23 db0 db23 undefined nop condition db0 input word specifies register to be read selected register data clocked out 06064-004 figure 4. readback timing diagram 200a i ol 200a i oh v oh (min) or v ol (max) to output pin c l 50pf 06064-005 figure 5. load circuit for sdo timing diagram
ad5762r preliminary technical data rev. pra | page 10 of 33 absolute maximum ratings 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 to agnd, dgnd ?0.3 v to +17 v av ss to agnd, dgnd +0.3 v to ?17 v dv cc to dgnd ?0.3 v to +7 v digital inputs to dgnd ?0.3 v to dv cc + 0.3 v or 7 v (whichever is less) digital outputs to dgnd ?0.3 v to dv cc + 0.3 v refa, refb to agnd, pgnd ?0.3 v to av dd + 0.3v refout to agnd av ss to av dd temp av ss to av dd vouta, voutb to agnd av ss to av dd agnd to dgnd ?0.3 v to +0.3 v operating temperature range industrial ?40c to +85c storage temperature range ?65c to +150c junction temperature (t j max) 150c 32-lead tqfp ja thermal impedance 65c/w jc thermal impedance 12c/w lead temperature jedec industry standard soldering j-std-020 stresses above those listed under absolute maximum 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 listed in the operational sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. esd caution esd (electrostatic discharge) sensitive device. electrosta tic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge with out detection. although this product features proprietary esd protection circuitry, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd precautions are recommended to avoid performance degradation or loss of functionality.
preliminary technical data ad5762r rev. pra | page 11 of 33 pin configuration and fu nction descriptions ad5762r top view (not to scale) sync sclk sdin sdo clr ldac d1 d0 agnd a vouta voutb agndb nc nc nc nc rstout rstin dgnd dv cc av dd pgnd iscc av ss bin/2scom p av dd av ss temp refgnd refout refb refa 1 32 25 916 8 24 17 pin 1 indicator figure 6. pin configuration table 5. pin function descriptions pin no. mnemonic description 1 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. 2 sclk serial clock input. data is cl ocked into the shift register on the falling edge of sclk. this operates at clock speeds up to 30 mhz. 3 sdin serial data input. data must be valid on the falling edge of sclk. 4 sdo serial data output. used to clock data from the serial register in daisy-chain or readback mode. 5 1 clr 1 negative edge triggered input. asserting th is pin sets the dac registers to 0x0000. 6 ldac load dac. logic input. this is used to update the dac registers and consequently the analog outputs. when tied permanentl y low, the addressed dac register 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 output update is held off until the falling edge of ldac . in this mode, all analog outputs ca n be updated simultaneously on the falling edge of ldac . the ldac pin must not be left unconnected. 7, 8 d0, d1 d0 and d1 form a digital i/o port. the user can set up these pins as inputs or outputs that are configurable and readable over the serial interface. when configured as inputs, these pins have we ak internal pull-ups to dv cc . when programmed as outputs, d0 and d1 are referenced by dv cc and dgnd. 9 rstout reset logic output. this is the output from the on-chip voltage monitor used in the reset circuit. if desired, it can be used to control other system components. 10 rstin reset logic input. this input allows exte rnal access to the internal reset logic. applying a logic 0 to this input clamps the dac outputs to 0 v. in normal operation, rstin should be tied to logic 1. register values remain unchanged. 11 dgnd digital ground pin. 12 dv cc digital supply pin. voltage ranges from 2.7 v to 5.25 v. 13, 31 av dd positive analog supply pins. voltage ranges from 11.4 v to 16.5 v. 14 pgnd ground reference point for analog circuitry. 15, 30 av ss negative analog supply pins. voltage ranges from C11.4 v to C16.5 v. 16 iscc this pin is used in association with an optional external resistor to agnd to program the short-circuit current of the output ampl ifiers. refer to the features section for further details. 17 nc no internal connection 18 nc no internal connection
ad5762r preliminary technical data rev. pra | page 12 of 33 pin no. mnemonic description 19 voutb analog output voltage of dac b. buffered output with a nominal full-scale output range of 10 v. the output amplifier is capable of directly driving a 10 k?, 200 pf load. 20 agndb ground reference pin for dac b output amplifier. 21 agnda ground reference pin for dac a output amplifier. 22 vouta analog output voltage of dac a. buffered output with a nominal full-scale output range of 10 v. the output amplifier is capable of directly driving a 10 k?, 200 pf load. 23 nc do not connect to this pin 24 nc do not connect to this pin 25 refa external reference voltage. reference input range is 1 v to 7 v; programs the full- scale output voltage. refa = 5 v for specified performance. 26 refb external reference voltage. reference input range is 1 v to 7 v; programs the full- scale output voltage. refb = 5 v for specified performance. 27 refout reference output. this is the reference o utput from the internal voltage reference. the internal reference is 5 v 3 mv at 25c, with a reference tempco of 10 ppm/c. 28 refgnd reference ground return for the reference generator and buffers. 29 temp this pin provides an output voltage proporti onal to temperature. the output voltage is 1.4 v typical at 25c die temperature; variation with temperature is 5 mv/c. 32 bin/2scomp determines the dac coding. this pin should be hardwired to either dv cc or dgnd. when hardwired to dv cc , input coding is offset binary. when hardwired to dgnd, input coding is twos complement (see table 6). 1 internal pull-up device on this logic input. therefore, it can be left floating and defaults to a logic high condition.
preliminary technical data ad5762r rev. pra | page 13 of 33 terminology relative accuracy or integral nonlinearity (inl) for the dac, relative accuracy or integral nonlinearity (inl) is a measure of the maximum deviation, in lsbs, from a straight line passing through the endpoints of the dac transfer function. a typical inl vs. code plot can be seen in figure 7. differential nonlinearity (dnl) differential nonlinearity is the difference between the measured change and the ideal 1 lsb change between any two adjacent codes. a specified differential nonlinearity of 1 lsb maximum ensures monotonicity. this dac is guaranteed monotonic. a typical dnl vs. code plot can be seen in figure 9. monotonicity a dac is monotonic if the output either increases or remains constant for increasing digital input code. the ad5762r is monotonic over its full operating temperature range. 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 (offset binary coding) or 0x0000 (twos complement coding). a plot of bipolar zero error vs. temperature can be seen in figure 22. bipolar zero tc bipolar zero tc is the measure of the change in the bipolar zero error with a change in temperature. it is expressed in ppm fsr/c. full-scale error full-scale error is a measure of the output error when full-scale code is loaded to the dac register. ideally the output voltage should be 2 v ref ? 1 lsb. full-scale error is expressed in percentage of full-scale range. negative full-scale error/zero scale error negative full-scale error is the error in the dac output voltage when 0x0000 (offset binary coding) or 0x8000 (twos complement coding) is loaded to the dac register. ideally, the output voltage should be ?2 v ref . a plot of zero-scale error vs. temperature can be seen in figure 21. output voltage settling time output voltage settling time is the amount of time it takes for the output to settle to a specified level for a full-scale input change. 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 d/a 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 signal and is given in v/s. gain error gain error is a measure of the span error of the dac. it is the deviation in slope of the dac transfer characteristic from the ideal, expressed as a percentage of the full-scale range. a plot of gain error vs. temperature can be seen in figure 23. tot a l un a dju s te d e r ror total unadjusted error (tue) is a measure of the output error considering all the various errors. a plot of total unadjusted error vs. reference can be seen in figure 19. zero-scale error tc zero-scale error tc 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. gain error tc gain error tc is a measure of the change in gain error with changes in temperature. gain error tc is expressed in (ppm of fsr)/c. digital-to-analog glitch energy digital-to-analog glitch impulse is the impulse injected into the analog output when the input code in the dac register changes state. it is normally specified as the area of the glitch in nv-s and is measured when the digital input code is changed by 1 lsb at the major carry transition (0x7fff to 0x8000) (see figure 28). 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 dac output is not updated. it is specified in nv-s and measured with a full-scale code change on the data bus, that is, from all 0s to all 1s and vice versa. power supply sensitivity power supply sensitivity indicates how the output of the dac is affected by changes in the power supply voltage. dc crosstalk dc crosstalk is the dc change in the output level 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, and is expressed in lsbs. 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 subsequent 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 another dac. the energy of the glitch is expressed in nv-s.
ad5762r preliminary technical data rev. pra | page 14 of 33 channel-to-channel isolation channel-to-channel isolation is the ratio of the amplitude of the signal at the output of one dac to a sine wave on the reference input of another dac. it is measured in db. reference tc reference tc is a measure of the change in the reference output voltage with a change in temperature. it is expressed in ppm/c. digital crosstalk digital crosstalk is a measure of the impulse injected into the analog output of one dac from the digital inputs of another dac but is measured when the dac output is not updated. it is specified in nv-s and measured with a full-scale code change on the data bus, that is, from all 0s to all 1s and vice versa.
preliminary technical data ad5762r rev. pra | page 15 of 33 typical performance characteristics 1.0 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 0 10000 20000 30000 40000 50000 60000 inl error (lsb) dac code t a = 25c v dd /v ss = 15v refin = 5v 06064-007 figure 7. integral nonlinearity error vs. code, v dd /v ss = 15 v 1.0 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 0 10000 20000 30000 40000 50000 60000 inl error (lsb) dac code t a = 25c v dd /v ss = 12v refin = 5v 06064-008 figure 8. integral nonlinearity error vs. code, v dd /v ss = 12 v 1.0 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 0 10000 20000 30000 40000 50000 60000 dnl error (lsb) dac code t a = 25c v dd /v ss = 15v refin = 5v 06064-011 figure 9. differential nonlinearity error vs. code, v dd /v ss = 15 v 1.0 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 0.8 0 10000 20000 30000 40000 50000 60000 dnl error (lsb) dac code t a = 25c v dd /v ss = 12v refin = 5v 06064-012 figure 10. differential nonlinearity error vs. code, v dd /v ss = 12 v 0.5 0.4 0.3 0.2 0.1 ?0.2 ?0.1 0 ?40 100 ?20 0 20 40 60 80 inl error (lsb) temperature (c) t a = 25c v dd /v ss = 15v refin = 5v 06064-015 figure 11. integral nonlinearity error vs. temperature, v dd /v ss = 15 v 0.5 0.4 0.3 0.2 0.1 ?0.1 0 ?40 100 ?20 0 20 40 60 80 inl error (lsb) temperature (c) t a = 25c v dd /v ss = 12v refin = 5v 06064-016 figure 12. integral nonlinearity error vs. temperature, v dd /v ss = 12 v
ad5762r preliminary technical data rev. pra | page 16 of 33 0.15 0.10 0.05 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 ?40 100 ?20 0 20 40 60 80 dnl error (lsb) temperature (c) t a = 25c v dd /v ss = 15v refin = 5v 06064-019 figure 13. differential nonlinearity error vs. temperature, v dd /v ss = 15 v 0.15 0.10 0.05 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 ?40 100 ?20 0 20 40 60 80 dnl error (lsb) temperature (c) t a = 25c v dd /v ss = 12v refin = 5v 06064-020 figure 14. differential nonlinearity error vs. temperature, v dd /v ss = 12 v 0.5 0.4 0.3 0.2 0.1 0 ?0.2 ?0.1 11.4 16.4 15.4 14.4 13.4 12.4 inl error (lsb) supply voltage (v) t a = 25c refin = 5v 06064-023 figure 15. integral nonlinearity error vs. supply voltage 0.15 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 11.4 16.4 15.4 14.4 13.4 12.4 dnl error (lsb) supply voltage (v) t a = 25c refin = 5v 06064-025 figure 16. differential nonlinearity error vs. supply voltage 0.8 ?1.0 ?0.8 ?0.6 ?0.4 ?0.2 0 0.2 0.4 0.6 17 56 4 3 2 inl error (lsb) reference voltage (v) t a = 25c 06064-027 figure 17. integral nonlinearity error vs. reference voltage, v dd /v ss = 16.5 v 0.4 0.3 0.2 0.1 ?0.4 ?0.3 ?0.2 ?0.1 0 17 56 4 3 2 dnl error (lsb) reference voltage (v) t a = 25c 06064-031 figure 18. differential nonlinearity error vs. reference voltage, v dd /v ss = 16.5 v
preliminary technical data ad5762r rev. pra | page 17 of 33 0.8 0.6 0.4 ?0.4 ?0.2 0 0.2 ?40 100 80 60 40 20 0 ?20 bipolar zero error (mv) temperature (c) refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06064-039 figure 19. total unadjusted error vs. reference voltage, v dd /v ss = 16.5 v 14 13 12 11 10 9 8 11.4 16.4 15.4 14.4 13.4 12.4 current (ma) v dd /v ss (v) t a = 25c refin = 5v |i ss | |i dd | 06064-037 figure 20. i dd /i ss vs. v dd /v ss 0.25 ?0.25 ?0.20 ?0.15 ?0.10 ?0.05 0 0.05 0.10 0.15 0.20 ?40 100 80 60 40 20 0 ?20 zero-scale error (mv) temperature (c) refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06064-038 figure 21. zero-scale error vs. temperature 0.8 0.6 0.4 ?0.4 ?0.2 0 0.2 ?40 100 80 60 40 20 0 ?20 bipolar zero error (mv) temperature (c) refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06064-039 figure 22. bipolar zero error vs. temperature 1.4 0.6 0.8 1.0 1.2 0.4 ?0.2 0 0.2 ?40 100 80 60 40 20 0 ?20 gain error (mv) temperature (c) refin = 5v v dd /v ss = 15v v dd /v ss = 12v 06064-040 figure 23. gain error vs. temperature 0.0014 0.0013 0.0012 0.0011 0.0010 0.0009 0.0008 0.0007 0.0006 05.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 di cc (ma) v logic t a = 25c 5v 3v 06064-041 figure 24. di cc vs. logic input voltage
ad5762r preliminary technical data rev. pra | page 18 of 33 7000 3000 4000 5000 6000 2000 ?1000 0 1000 ?10 10 5 0 ?5 output voltage delta (v) source/sink current (ma) 05303-042 v dd /v ss = 15v v dd /v ss = 12v t a = 25c refin = 5v ri scc = 6k ? figure 25. source and sink capability of output amplifier with positive full scale loaded 10000 7000 8000 9000 3000 4000 5000 6000 2000 ?1000 0 1000 ?12 8 3 ?2 ?7 output voltage delta (v) source/sink current (ma) 05303-043 15v supplies 12v supplies t a = 25c refin = 5v ri scc = 6k ? figure 26. source and sink capability of output amplifier with negative full scale loaded ch1 3.00v m1.00s ch1 ?120mv 1 v dd /v ss = 15v t a = 25c refin = 5v 1s/div 06064-044 figure 27. full-scale settling time ? 4 ?6 ?8 ?10 ?12 ?14 ?16 ?18 ?20 ?22 ?24 ?26 ?2.0?1.5?1.0?0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 v out (mv) time (s) v dd /v ss = 12v, refin = 5v, t a = 25c, 0x8000 to 0x7fff, 500ns/div 06064-047 figure 28. major code transition glitch energy, v dd /v ss = 12 v ch4 50.0v m1.00s ch4 26v 4 v dd /v ss = 15v midscale loaded refin = 0v 50v/div 06064-048 figure 29. peak-to-peak no ise (100 khz bandwidth) ch1 10.0v b w ch3 10.0mv b w t 29.60% ch2 10.0v m100s a ch1 7.80mv 1 2 3 v dd /v ss = 12v, refin = 5v, t a = 25c, ramp time = 100s, load = 200pf||10k ? t 06064-055 figure 30. vout vs. v dd /v ss on power-up
preliminary technical data ad5762r rev. pra | page 19 of 33 10 9 8 7 6 5 4 3 2 1 0 0 120 100 80 60 40 20 short-circuit current (ma) ri scc (k ? ) v dd /v ss = 15v t a = 25c refin = 5v 06064-050 figure 31. short-circuit current vs. ri scc ch1 10.0v b w ch3 5.00v b w t 29.60% ch2 10.0v m400s a ch1 7.80mv 1 2 3 v dd /v ss = 12v t a = 25c t 06064-054 figure 32. refout turn-on transient ch1 50.0v m1.00s a ch1 15v 1 v dd /v ss = 12v t a = 25c, 10f capacitor on ref out 50v/div 06064-052 figure 33. refout output noise 100 khz bandwidth m1.00s a ch1 18mv 1 v dd /v ss = 12v t a = 25c 5v/div 06064-053 figure 34. refout output noise 0.1 hz to 10 hz figure 35. refout load regulation figure 36. refout histogra m of thermal hysteresis
ad5762r preliminary technical data rev. pra | page 20 of 33 figure 37. temp voltage vs. temperature
preliminary technical data ad5762r rev. pra | page 21 of 33 theory of operation the ad5762r is a dual, 16-bit, serial input, bipolar voltage output dac and operates from supply voltages of 11.4 v to 16.5 v and has a buffered output voltage of up to 10.5263 v. data is written to the ad5762r in a 24-bit word format, via a 3-wire serial interface. the ad5762r also offers an sdo pin, which is available for daisy chaining or readback. the ad5762r incorporates a power-on reset circuit, which ensures that the dac registers power up loaded with 0x0000. the ad5762r features a digital i/o port that can be programmed via the serial interface, an analog die temperature sensor, on-chip 10 ppm/c voltage reference, on-chip reference buffers and per channel digital gain and offset registers. dac architecture the dac architecture of the ad5762r consists of a 16-bit current mode segmented r-2r dac. the simplified circuit diagram for the dac section is shown in figure 38. 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 the 15 matched resistors to either agnd or iout. the remaining 12 bits of the data word drive switches s0 to s11 of the 12-bit r- 2r ladder network. 2r e15 v ref 2r e14 e1 2r s11 rr r 2r s10 2r 12-bit, r-2r ladder 4 msbs decoded into 15 equal segments v out 2r s0 2r agnd r/8 i out 06064-060 figure 38. dac ladder structure reference buffers the ad5762r can operate with either an external or an internal reference. the reference input has an input range up to 7 v. this input voltage is then used to provide a buffered positive and negative reference for the dac cores. the positive reference is given by + v ref = 2 v refin while the negative reference to the dac cores is given by ?v ref = ?2 v refin these positive and negative reference voltages (along with the gain register values) define the output ranges of the dacs. serial interface the ad5762r 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. 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. the input register consists of a read/write bit, three register select bits, three dac address bits and 16 data bits as shown in table 7. the timing diagram for this operation is shown in figure 2. upon power-up, the dac registers are loaded with zero code (0x0000) and the outputs are clamped to 0 v via a low impedance path. the outputs can be updated with the zero code value by asserting either ldac or clr . the corresponding output voltage depends on the state of the bin/ 2scomp pin. if the bin/ 2scomp pin is tied to dgnd, then the data coding is twos complement and the outputs update to 0 v. if the bin/ 2scomp pin is tied to dv cc , then the data coding is offset binary and the outputs update to negative full scale. to have the outputs power-up with zero code loaded to the outputs, the clr pin should be held low during power-up. standalone operation the serial interface works with both a continuous and noncon- tinuous serial clock. a continuous sclk source can only be used if sync is held low for the correct number of clock cycles. in gated clock mode, a burst clock containing the exact number of clock cycles must be used and sync must be taken high after the final clock to latch the data. the first falling edge of sync starts the write cycle. exactly 24 falling clock edges must be applied to sclk before sync is brought back high again. if sync is brought high before the 24 th falling sclk edge, then the data written is invalid. if more than 24 falling sclk edges are applied before sync is brought high, then the input data is also invalid. the input register addressed is updated on the rising edge of sync . in order for another serial transfer to take place, sync must be brought low again. after the end of the serial data transfer, data is automatically transferred from the input shift register to the addressed register. when the data has been transferred into the chosen register of the addressed dac, all dac registers and outputs can be updated by taking ldac low.
ad5762r preliminary technical data rev. pra | page 22 of 33 68hc11* miso sync sdin sclk mosi sck pc7 pc6 ldac sdo sync sclk ldac sdo sync sclk ldac sdo sdin sdin *additional pins omitted for clarity ad5762r* ad5762r* ad5762r* figure 39. daisy chaining the ad5762r daisy-chain operation for systems that contain several devices, the sdo pin can be used to daisy chain several devices together. this daisy-chain mode can be useful in system diagnostics and in reducing the number of serial interface lines. the first falling edge of sync starts the write cycle. the sclk is continuously applied to the input shift register when sync is low. if more than 24 clock pulses are applied, the data ripples out of the shift register and appears on the sdo line. this data is clocked out on the rising edge of sclk and is valid on the falling edge. by connecting the sdo of the first device to the sdin input of the next device in the chain, a multidevice interface is constructed. each device in the system requires 24 clock pulses. therefore, the total number of clock cycles must equal 24n, where n is the total number of ad5762r devices in the chain. when the serial transfer to all devices is complete, sync is taken high. this latches the input data in each device in the daisy chain and prevents any further data from being clocked into the input shift register. the serial clock can be a continuous or a gated clock. a continuous sclk source can only be used if sync is held low for the correct number of clock cycles. in gated clock mode, a burst clock containing the exact number of clock cycles must be used and sync must be taken high after the final clock to latch the data. readback operation before a readback operation is initiated, the sdo pin must be enabled by writing to the function register and clearing the sdo disable bit; this bit is cleared by default. readback mode is invoked by setting the r/ w bit = 1 in the serial input register write. with r/ w = 1, bit a2 to bit a0, in association with bit reg2, bit reg1, and bit reg0, select the register to be read. the remaining data bits in the write sequence are dont care. during the next spi write, the data appearing on the sdo output contain the data from the previously addressed register. for a read of a single register, the nop command can be used in clocking out the data from the selected register on sdo. the readback diagram in figure 4 shows the readback sequence. for example, to read back the fine gain register of channel a on the ad5762r, the following sequence should be implemented: 1. write 0xa0xxxx to the ad5762r input register. this configures the ad5762r for read mode with the fine gain register of channel a selected. note that all the data bits, db15 to db0, are dont care. 2. follow this with a second write, a nop condition, 0x00xxxx. during this write, the data from the fine gain register is clocked out on the sdo line, that is, data clocked out contains the data from the fine gain register in bit db5 to bit db0. simultaneous updating via ldac depending on the status of both sync and ldac , and after data has been transferred into the input register of the dacs, there are two ways in which the dac registers and dac outputs can be updated. individual dac updating in this mode, ldac is held low while data is being clocked into the input shift register. the addressed dac output is updated on the rising edge of sync . simultaneous updating of all dacs in this mode, ldac is held high while data is being clocked into the input shift register. all dac outputs are updated by taking ldac low any time after sync has been taken high. the update now occurs on the falling edge of ldac .
preliminary technical data ad5762r rev. pra | page 23 of 33 v out dac register interface logic output i/v amplifier ldac sdo sdin 16-bit dac v refin sync input register sclk 06064-062 figure 40. simplified serial interface of input loading circuitry for one dac channel transfer function table 6 shows the ideal input code to output voltage relationship for the ad5762r for both offset binary and twos complement data coding. table 6. ideal output voltage to input code relationship for the ad5762r digital input analog output offset binary data coding msb lsb v out 1111 1111 1111 1111 +2 v refin (32767/32768) 1000 0000 0000 0001 +2 v refin (1/32768) 1000 0000 0000 0000 0 v 0111 1111 1111 1111 ? 2 v refin (1/32768) 0000 0000 0000 0000 ? 2 v refin (32767/32768) twos complement data coding msb lsb v out 0111 1111 1111 1111 +2 v refin (32767/32768) 0000 0000 0000 0001 +2 v refin (1/32768) 0000 0000 0000 0000 0 v 1111 1111 1111 1111 ? 2 v refin (1/32768) 1000 0000 0000 0000 ? 2 v refin (32767/32768) the output voltage expression for the ad5762r is given by ? ? ? ? ? ? + ? = d v v v refin refin out where: d is the decimal equivalent of the code loaded to the dac. v refin is the reference voltage applied at the refa, refb pins. asynchronous clear ( clr ) clr is a negative edge triggered clear that allows the outputs to be cleared to either 0 v (twos complement coding) or negative full scale (offset binary coding). it is necessary to maintain clr low for a minimum amount of time (see figure 2) for the operation to complete. when the clr signal is returned high, the output remains at the cleared value until a new value is programmed. if at power-on clr is at 0 v, then all dac outputs are updated with the clear value. a clear can also be initiated through software by writing the command 0x04xxxx to the ad5762r.
ad5762r preliminary technical data rev. pra | page 24 of 33 table 7. ad5762r input register format msb lsb db23 db22 db21 db20 db19 db18 db17 db16 db15 db14 db13 db12 db11 db10 db9 db8 db7 db6 db5 db4 db3 db2 db1 db0 r/ w 0 reg2 reg1 reg0 a2 a1 a0 data table 8. input register bit functions register function r/w indicates a read from or a write to the addressed register. reg2, reg1, reg0 used in association with the address bits to determine if a read or write operation is to the data register, offset register, gain register, or function register. reg2 reg1 reg0 function 0 0 0 function register 0 1 0 data register 0 1 1 coarse gain register 1 0 0 fine gain register 1 0 1 offset register a2, a1, a0 these bits are used to decode the dac channels. a2 a1 a0 channel address 0 0 0 dac a 0 0 1 dac b 1 0 0 both dacs d15:d0 data bits. function register the function register is addressed by setting the three reg bits to 000. the values written to the address bits and the data bi ts determine the function addressed. the functions available via the function register are outlined in table 9 and table 10. table 9. function register options reg2 reg1 reg0 a2 a1 a0 db15:db6 db5 db4 db3 db2 db1 db0 0 0 0 0 0 0 nop, data = dont care 0 0 0 0 0 1 dont care local- ground- offset adjust d1 direction d1 value d0 direction d0 value sdo disable 0 0 0 1 0 0 clr, data = dont care 0 0 0 1 0 1 load, data = dont care table 10. explanation of function register options option description nop no operation instruction used in readback operations. local-ground- offset adjust set by the user to enable local-ground-offset adjust function . cleared by the user to disable local-ground-offset adjust function (default). refer to features section for further details. d0/d1 direction set by the user to enable d0/d1 as outputs . cleared by the user to enable d0/d1 as inputs (default). refer to the features section for further details. d0/d1 value i/o port status bits. logic values written to these location s determine the logic outputs on the d0 and d1 pins when configured as outputs. these bits indicate the status of the d0 and d1 pins when th e i/o port is active as an input. when enabled as inputs, these bits are do nt cares during a write operation. sdo disable set by the user to disabl e the sdo output. cleared by the user to enable the sdo output (default). clr addressing this function resets the da c outputs to 0 v in twos complement mode and negative full scale in binary mode. load addressing this function updates the dac registers and consequently the analog outputs.
preliminary technical data ad5762r rev. pra | page 25 of 33 data register the data register is addressed by setting the three reg bits to 010. the dac address bits select with which dac channel the dat a transfer is to take place (see table 8). the data bits are in po sitions db15 to db0 for the ad5762r as shown in table 11. table 11. programming the ad5762r data register reg2 reg1 reg0 a2 a1 a0 db15 db14 db13 db12 db11 db10 db9 db8 db7 db6 db5 db4 db3 db2 db1 db0 0 1 0 dac address 16-bit dac data coarse gain register the coarse gain register is addressed by setting the three reg bits to 011. the dac address bits select with which dac channel the data transfer is to take place (see table 8). the coarse gain register is a 2-bit register and allows the user to select the output range of each dac as shown in table 13. table 12. programming the ad5762r coarse gain register reg2 reg1 reg0 a2 a1 a0 db15 . db2 db1 db0 0 1 1 dac address dont care cg1 cg0 table 13. output range selection output range cg1 cg0 10 v (default) 0 0 10.2564 v 0 1 10.5263 v 1 0 fine gain register the fine gain register is addressed by setting the three reg bits to 100. the dac address bits select with which dac channel th e data transfer is to take place (see table 8). the ad5762r fine gain register is a 6-bit register and allows the user to adjust the g ain of each dac channel by ?32 lsbs to +31 lsbs in 1 lsb steps as shown in table 14 and table 15. the adjustment is made to both the positive f ull-scale points and the negative full-scale points simultaneously, each point being adjusted by ? of one step. the fine gain register co ding is twos complement. table 14. programming ad5762r fine gain register reg2 reg1 reg0 a2 a1 a0 db15:db6 db5 db4 db3 db2 db1 db0 1 0 0 dac address dont care fg5 fg4 fg3 fg2 fg1 fg0 table 15. ad5762r fine gain register options gain adjustment fg5 fg4 fg3 fg2 fg1 fg0 +31 lsbs 0 1 1 1 1 1 +30 lsbs 0 1 1 1 1 0 - - - - - - no adjustment (default) 0 0 0 0 0 0 - - - - - - ?31 lsbs 1 0 0 0 0 1 ?32 lsbs 1 0 0 0 0 0 offset register the offset register is addressed by setting the three reg bits to 101. the dac address bits select with which dac channel the d ata transfer is to take place (see table 8). the ad5762r offset register is an 8-bit register and allows the user to adjust the off set of each channel by ?16 lsbs to +15.875 lsbs in steps of ? lsb as shown in table 16 and table 17. the offset register coding is twos com plement. table 16. programming the ad5762r offset register reg2 reg1 reg0 a2 a1 a0 db15:db8 db7 db6 db5 db4 db3 db2 db1 db0 1 0 1 dac address dont care of7 of6 of5 of4 of3 of2 of1 of0
ad5762r preliminary technical data rev. pra | page 26 of 33 table 17. ad5762r offset register options offset adjustment of7 of6 of5 of4 of3 of2 of1 of0 +15.875 lsbs 0 1 1 1 1 1 1 1 +15.75 lsbs 0 1 1 1 1 1 1 0 - - - - - - - - no adjustment (default) 0 0 0 0 0 0 0 0 - - - - - - - - ?15.875 lsbs 1 0 0 0 0 0 0 1 ?16 lsbs 1 0 0 0 0 0 0 0
preliminary technical data ad5762r rev. pra | page 27 of 33 offset and gain adjustment worked example using the information provided in the previous section, the following worked example demonstrates how the ad5762r functions can be used to eliminate both offset and gain errors. as the ad5762r is factory calibrated, offset and gain errors should be negligible. however, errors can be introduced by the system that the ad5762r is operating within, for example, a voltage reference value that is not equal to +5 v introduces a gain error. an output range of 10 v and twos complement data coding is assumed. removing offset error the ad5762r can eliminate an offset error in the range of ?4.88 mv to +4.84 mv with a step size of ? of a 16-bit lsb. calculate the step size of the offset adjustment, v size step adjust offset 14 . 38 8 2 20 16 = = measure the offset error by programming 0x0000 to the data register and measuring the resulting output voltage, for this example the measured value is +614 v. how many offset adjustment steps does this value represent? steps v v size step offset value offset measured steps of number 16 14 . 38 614 = = = the offset error measured is positive, therefore, a negative adjustment of 16 steps is required. the offset register is 8 bits wide and the coding is twos complement. the required offset register value can be calculated as follows: convert adjustment value to binary; 00010000. convert this to a negative twos complement number by inverting all bits and adding 1; 11110000. 11110000 is the value that should be programmed to the offset register. note: this twos complement conversion is not necessary in the case of a positive offset adjustment. the value to be programmed to the offset register is simply the binary representation of the adjustment value. removing gain error the ad5762r can eliminate a gain error at negative full-scale output in the range of ?9.77 mv to +9.46 mv with a step size of ? of a 16-bit lsb. calculate the step size of the gain adjustment v size step adjust gain 59 . 152 2 2 20 16 = = measure the gain error by programming 0x8000 to the data register and measuring the resulting output voltage. the gain error is the difference between this value and ?10 v, for this example, the gain error is ?1.2 mv. how many gain adjustment steps does this value represent? steps v mv size step gain value gain measured steps of number 8 59 . 152 2 . 1 = = = the gain error measured is negative (in terms of magnitude); therefore, a positive adjustment of eight steps is required. the gain register is 6 bits wide and the coding is twos complement, the required gain register value can be determined as follows: convert adjustment value to binary; 001000. the value to be programmed to the gain register is simply this binary number.
ad5762r preliminary technical data rev. pra | page 28 of 33 ad5762r features analog output control in many industrial process control applications, it is vital that the output voltage be controlled during power-up and during brownout conditions. when the supply voltages are changing, the vout pins are clamped to 0 v via a low impedance path. to prevent the output amp being shorted to 0 v during this time, transmission gate g1 is also opened (see figure 41). these conditions are maintained until the power supplies stabilize and a valid word is written to the dac register. at this time, g2 opens and g1 closes. both transmission gates are also externally controllable via the reset in ( rstin ) control input. for instance, if rstin is driven from a battery supervisor chip, the rstin input is driven low to open g1 and close g2 on power- off or during a brownout. conversely, the on-chip voltage detector output ( rstout ) is also available to the user to control other parts of the system. the basic transmission gate functionality is shown in figure 41. g1 g2 rstout rstin vouta agnda voltage monitor and control 06064-063 figure 41. analog output control circuitry digital offset and gain control the ad5762r incorporates a digital offset adjust function with a 16 lsb adjust range and 0.125 lsb resolution. the gain register allows the user to adjust the ad5762rs full-scale output range. the full-scale output can be programmed to achieve full-scale ranges of 10 v, 10.25 v, and 10.5 v. a fine gain trim is also available. programmable short-circuit protection the short-circuit current of the output amplifiers can be pro- grammed by inserting an external resistor between the iscc pin and pgnd. the programmable range for the current is 500 a to 10 ma, corresponding to a resistor range of 120 k ? to 6 k? . the resistor value is calculated as follows: isc r 60 = if the iscc pin is left unconnected, the short circuit current limit defaults to 5 ma. it should be noted that limiting the short circuit current to a small value can affect the slew rate of the output when driving into a capacitive load, therefore, the value of short-circuit current programmed should take into account the size of the capacitive load being driven. digital i/o port the ad5762r contain a 2-bit digital i/o port (d1 and d0), these bits can be configured as inputs or outputs independently, and can be driven or have their values read back via the serial interface. the i/o port signals are referenced to dv cc and dgnd. when configured as outputs, they can be used as control signals to multiplexers or can be used to control calibration circuitry elsewhere in the system. when configured as inputs, the logic signals from limit switches, for example can be applied to d0 and d1 and can be read back via the digital interface. die temperature sensor the on-chip die temperature sensor provides a voltage output that is linearly proportional to the centigrade temperature scale. its nominal output voltage is 1.4 v at +25c die temperature, varying at 5 mv/c, giving a typical output range of 1.175 v to 1.9 v over the full temperature range. its low output impedance, and linear output simplify interfacing to temperature control circuitry and a/d converters. the temperature sensor is provided as more of a convenience rather than a precise feature; it is intended for indicating a die temperature change for recalibration purposes. local ground offset adjust the ad5762r incorporates a local-ground-offset adjust feature which when enabled in the function register adjusts the dac outputs for voltage differences between the individual dac ground pins and the refgnd pin ensuring that the dac output voltages are always with respect to the local dac ground pin. for instance, if pin agnda is at +5 mv with respect to the refgnd pin and vouta is measured with respect to agnda then a ?5mv error results, enabling the local-ground- offset adjust feature adjusts vouta by +5 mv, eliminating the error.
preliminary technical data ad5762r rev. pra | page 29 of 33 applications information typical operating circuit figure 42 shows the typical operating circuit for the ad5762r. the only external components needed for this precision 16-bit dac are decoupling capacitors on the supply pins and reference inputs, and an optional short-circuit current setting resistor. because the ad5762r incorporates a voltage reference and reference buffers, it eliminates the need for an external bipolar reference and associated buffers. this leads to an overall savings in both cost and board space. in figure 42, v dd and v ss are both connected to 15 v, but v dd and v ss can operate with supplies from 11.4 v to 16.5 v. in figure 42, agnda and agndb are connected to refgnd. 1 2 3 4 5 6 7 8 23 22 21 18 19 20 24 17 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 ad5762r sync sclk sdin sdo d0 ldac clr d1 nc vouta agnda nc voutb agndb nc nc rstout rstin dgnd dv cc av dd pgnd av ss iscc bin/2scomp avdd avss temp refgnd refout refb refa sync sclk sdin sdo ldac d0 d1 rstout rstin bin/2scomp +5v +5v +15v ?15v +15 v ? 15 v voutb vouta 100nf 100nf 100nf 10f 100nf 100nf 10f 10f 10f temp 10f 10f figure 42. typical operating circuit precision voltage reference selection to achieve the optimum performance from the ad5762r over its full operating temperature range, an external voltage reference must be used. thought should be given to the selection of a precision voltage reference. the voltage applied to the reference input is used to provide a buffered positive and negative 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 could 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 ad- justment can also be used at 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 drift 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 should be chosen to reduce the dependence of the dac output voltage on ambient conditions. in high accuracy applications, which have a relatively low noise budget, reference output voltage noise needs to be considered. choosing a reference with as low an output 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 the circuit bandwidth increases, filtering the output of the reference may be required to minimize the output noise. table 18. some precision references recommended for use with the ad5762r part no. initial accuracy(mv max) long-term drift (ppm typ) te mp drift (ppm/c max) 0.1 hz to 10 hz noise (v p-p typ) adr435 6 30 3 3.4 ADR425 6 50 3 3.4 adr02 5 50 3 15 adr395 6 50 25 5 ad586 2.5 15 10 4
ad5762r preliminary technical data rev. pra | page 30 of 33 layout guidelines in any circuit where accuracy is important, careful consider- ation of the power supply and ground return layout helps to ensure the rated performance. the printed circuit board on which the ad5762r is mounted shou ld be designed so that the analog and digital sections are separated and confined to certain areas of the board. if the ad5762r 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 ad5762r should have ample supply bypassing of 10 f in parallel with 0.1 f on each su pply 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 seri es resistance (esr) and low effective series inductance (esi) 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. the power supply lines of the ad5762r should use as large a trace as possible to provide low impedance paths and reduce the effects of glitches on the power supply line. fast switching signals, such as clocks, should be shielded with digital ground to avoid 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 lines helps reduce cross-talk between them (not required on a multilayer board, which has a separate ground plane, however, it is helpful to separate the lines). it is essential to minimize noise on the reference inputs, because it couples through to the dac output. avoid crossover of digital and analog signals. tr aces on opposite sides of the board should run at right angles to each other. this reduces the effects of feed through on the board. a microstrip technique is recommended, but not always possible with a double-sided board. in this technique, the component side of the board is dedicated to ground plane, while signal traces are placed on the solder side. galvanically isolated 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 might occur. isocouplers provide voltage isolation in excess of 2.5 kv. the serial loading structure of the ad5762r makes it ideal for isolated interfaces, because the number of interface lines is kept to a minimum. figure 43 shows a 4-channel isolated interface to the ad5762r using an adum1400. for more information, go to www.analog.com. 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 to sync v oc encode decode v id control out to ldac v od encode decode controller adum1400 1 1 additional pins omitted for clarity 06064-065 figure 43. isolated interface microprocessor interfacing microprocessor interfacing to the ad5762r is via a serial bus that uses standard 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 synchronization signal. the ad5762r requires a 24-bit data-word with data valid on the falling edge of sclk. for all the interfaces, the dac output update can be done automatically when all the data is clocked in, or it can be done under the control of ldac. the contents of the dac register can be read using the readback function. ad5762r to mc68hc11 interface figure 44 shows an example of a serial interface between the ad5762r and the mc68hc11 microcontroller. the serial peripheral interface (spi) on the mc68hc11 is configured for master mode (mstr = 1), clock polarity bit (cpol = 0), and the clock phase bit (cpha = 1). the spi is configured by writing to the spi control register (spcr) (see the 68hc11user manual) . sck of the mc68hc11 drives the sclk of the ad5762r, the mosi output drives the serial data line (din) of the ad5762r, and the miso input is driven from sdo. the sync is driven from one of the port lines, in this case pc7.
preliminary technical data ad5762r rev. pra | page 31 of 33 when data is being transmitted to the ad5762r, the sync line (pc7) is taken low and data is transmitted msb first. data appearing on the mosi output is valid on the falling edge of sck. eight falling clock edges occur in the transmit cycle, so, in order to load the required 24-bit word, pc7 is not brought high until the third 8-bit word has been transferred to the dacs input shift register. mc68hc11 1 1 additional pins omitted for clarity ad5762r 1 sdo miso sdin mosi sclk sck sync pc7 06064-066 figure 44. ad5762r to mc68hc11 interface ldac is controlled by the pc6 port output. the dac can be updated after each 3-byte transfer by bringing ldac low. this example does not show other serial lines for the dac. for example, if clr were used, it could be controlled by port output pc5. ad5762r to 8xc51 interface the ad5762r requires a clock synchronized to the serial data. for this reason, the 8xc51 must be operated in mode 0. in this mode, serial data enters and exits through rxd, and a shift clock is output on txd. p3.3 and p3.4 are bit programmable pins on the serial port and are used to drive sync and ldac , respectively. the 8cx51 provides the lsb of its sbuf register as the first bit in the data stream. the user must ensure that the data in the sbuf register is arranged correctly, because the dac expects msb first. when data is to be transmitted to the dac, p3.3 is taken low. data on rxd is clocked out of the microcontroller on the rising edge of txd and is valid on the falling edge. as a result, no glue logic is required between this dac and the microcontroller interface. 8xc51 1 1 additional pins omitted for clarity ad5762r 1 sclk txd sdin rxd sync p3.3 ldac p3.4 06064-067 figure 45. ad5762r to 8xc51 interface the 8xc51 transmits data in 8-bit bytes with only eight falling clock edges occurring in the transmit cycle. because the dac expects a 24-bit word, sync (p3.3) must be left low after the first eight bits are transferred. after the third byte has been transferred, the p3.3 line is taken high. the dac can be updated using ldac via p3.4 of the 8xc51. ad5762r to adsp2101/adsp2103 interface an interface between the ad5762r and the adsp2101/ adsp2103 is shown in figure 46. the adsp2101/ adsp2103 should be set up to operate in the sport transmit alternate framing mode. the adsp2101/adsp2103 are programmed through the sport control register and should be configured as follows: internal clock operation, active low framing, and 24- bit word length. transmission is initiated by writing a word to the tx register after the sport has been enabled. as the data is clocked out of the dsp on the rising edge of sclk, no glue logic is required to interface the dsp to the dac. in the interface shown, the dac output is updated using the ldac pin via the dsp. alterna- tively, the ldac input could be tied permanently low, and then the update takes place automatically when tfs is taken high. sclk sdin sync dt sclk rfs adsp2101/ adsp2103 1 1 additional pins omitted for clarity sdo dr tfs ldac fo ad5762r 1 06064-068 figure 46. ad5762r to adsp2101/adsp2103 interface ad5762r to pic16c6x/7x interface the pic16c6x/7x synchronous serial port (ssp) is configured as an spi master with the clock polarity bit set to 0. this is done by writing to the synchronous serial port control register (sspcon). see the pic16/17 microcontroller user manual . in this example, i/o port ra1 is being used to pulse sync and enable the serial port of the ad5762r. this microcontroller transfers only eight bits of data during each serial transfer operation; therefore, three consecutive write operations are needed. figure 47 shows the connection diagram.
ad5762r preliminary technical data rev. pra | page 32 of 33 pic16c6x/7x 1 1 additional pins omitted for clarity ad5762r 1 sdo sdi/rc4 sdin sdo/rc5 sclk sclk/rc3 sync ra1 06064-069 figure 47. ad5762r to pic16c6x/7x interface evaluation board the ad5762r performance can be evaluated via the ad5764r evaluation board. the ad5764r comes with a full evaluation board to aid designers in evaluating the high performance of the part with a minimum of effort. all that is required with the evaluation board is a power supply and a pc. the ad5764r evaluation kit includes a populated, tested ad5764r printed circuit board. the evaluation board interfaces to the usb interface of the pc. software is available with the evaluation board, which allows the user to easily program the ad5764r. the software runs on any pc that has microsoft? windows? 2000/xp installed. an application note is available that gives full details on operating the evaluation board.
preliminary technical data ad5762r rev. pra | page 33 of 33 outline dimensions compliant to jedec standards ms-026aba 0.45 0.37 0.30 0.80 bsc lead pitch 7.00 bsc sq 9.00 bsc sq 124 25 32 8 9 17 16 1.20 max 0.75 0.60 0.45 1.05 1.00 0.95 0.20 0.09 0.08 max coplanarity seating plane 0 min 7 3.5 0 0.15 0.05 view a rotated 90 ccw view a pin 1 top view (pins down) figure 48. 32-lead thin plastic dual flat package [tqfp] (su-32-2) dimensions shown in millimeters ordering guide 1 model function inl temperature internal reference package description package option ad5762rcsuz dual 16-bit dac 1 lsb max ?40c to +85c +5v 32-lead tqfp su-32-2 ad5762rcsuz-reel7 dual 16-bit dac 1 lsb max ?40c to +85c +5v 32-lead tqfp su-32-2 ?200 7 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. pr07248-0-12/07(pra)

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