View AD8656ARMZ_8471811.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

low noise, precision cmos amplifier d ata sheet ad8655 / ad8656 rev. d 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 par ties 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 respec tive owners. one technology way, p.o. box 9106, norwood, ma 02062 - 9106, u.s.a. tel: 781.329.4700 ? 2005 C 2013 analog devices, inc. all rights reserved. technical support www.analog.com f eatures low n oise: 2.7 nv/ hz @ f = 1 0 khz low offset voltage: 2 50 v max over v cm offset voltage drif t : 0.4 v/c typ and 2.3 v/c max bandwidth: 28 mhz rail - to - r ail input/ output unity gain stable 2.7 v to 5 .5 v operation ?40c to +125c operation q uali fied for automotive applications (ad8656) a pplications adc and dac b uffer s audio industrial controls precision filters digital scales automotive collision avoidance pll f ilters p in c onfigurations nc 1 ? in 2 +in 3 v ? 4 nc 8 v+ 7 out 6 nc 5 ad8655 top view (not to scale) 05304-048 nc = no connect out a 1 ? in a 2 +in a 3 v ? 4 v+ 8 out b 7 ? in b 6 +in b 5 ad8656 top view (not to scale) 05304-059 figure 1 . ad8655 8- lead mso p (rm - 8) figure 2 . ad8656 8- lead msop (rm - 8) nc 1 ?in 2 +in 3 v? 4 nc 8 v+ 7 out 6 nc 5 nc = no connect ad8655 top view (not to scale) 05304-049 out a 1 ? in a 2 +in a 3 v ? 4 v+ 8 out b 7 ? in b 6 +in b 5 ad8656 top view (not to scale) 05304-060 figure 3 . ad8655 8- lead soic (r - 8) figure 4 . ad8656 8- lead soic (r - 8) g eneral d escription the ad8655 /ad8656 are the indus trys lowest noise, precision c mos amplif ier s . they leverage the analog devices digitri m? technology to achieve high dc accuracy. the ad8655/ad8656 provide low noise (2.7 nv/ hz @ 10 khz), low thd + n (0.0007%), and high precision performance (250 v max over v cm ) to low voltage applications. the ability to swing rail - to - rail at the input and output enables designers to buffer analog - to - digital converter s (adcs) and other wide dynamic range devices in single - supply systems. the high precision performance of the ad8655/ad8656 improves the resolution and dynamic range in low voltage applications. audio applications, such as microphone pre - amps and audio mixing co nsoles, benefit from the low noise, low distortion , and high output current capability of the ad 8655/ ad8656 to reduce system level noise performance and main tain audio fidelity. the high precision and rail - to - rail input and output of the ad8655/ad8656 benefit data acquisition, process controls , and pll filter applications. the ad8655/ad8656 are full y specified over the ? 40c to +125c temperature range. the ad8655 /ad8656 are available in pb - free , 8 - lead msop and soic packages .
ad8655 /ad8656 data sheet rev. d | page 2 of 20 table of contents specifications ..................................................................................... 3 absolute maximum ratings ............................................................ 5 esd caution .................................................................................. 5 typical performance characteristics ............................................. 6 theory of operation ...................................................................... 15 applications ..................................................................................... 16 input overvoltage protection ................................................... 16 input capacitance ....................................................................... 16 driving capacitive loads .......................................................... 16 layout, grounding, and bypassing consider ations .................. 18 power supply bypassing ............................................................ 18 grounding ................................................................................... 1 8 leakage current s ........................................................................ 18 outline dimensions ....................................................................... 19 ordering guide .......................................................................... 19 automotive products ................................................................. 19 revision history 6/13 rev. c to rev. d change to figure 57 ....................................................................... 16 5/13 rev. b to rev. c change to figure 57 ....................................................................... 16 9 /11 rev. a to rev. b changes to features section ............................................................ 1 updated outline dimensions ....................................................... 19 changes to ordering guide .......................................................... 19 added automotive products section ........................................... 19 6 /05 rev. 0 to rev. a added ad8656 ................................................................... universal added figure 2 and figure 4 ........................................................... 1 changes to s pecifications ................................................................ 3 changed caption of figure 12 and a dded figure 13 .................. 7 replaced figure 16 ........................................................................... 7 changed caption of figure 37 and added figu re 38 ................ 11 repla ced figure 47 ......................................................................... 13 added figure 55 .............................................................................. 14 changes to ordering guide .......................................................... 18 4 /05 revision 0: initial version
data sheet ad8655 /ad8656 rev. d | page 3 of 20 specifications v s = 5.0 v, v cm = v s /2, t a = 25c, unless otherwise specified. table 1 . pa rameter symbol conditions min typ max unit input characteristics offset voltage v os v cm = 0 v to 5 v 50 2 50 v ? 40c t a +125c 550 v offset voltage drift ? v os / ? t ? 40c t a +125c 0. 4 2.3 v/c input bias current i b 1 10 pa ? 40c t a +125c 5 00 pa inp ut offset current i os 10 pa ? 40c t a +125c 5 00 pa input voltage range 0 5 v common - mode rejection ratio cmrr v cm = 0 v to 5 v 85 100 db large signal voltage gain a vo v o = 0.2 v to 4.8 v, r l = 10 k?, v cm = 0 v 100 110 db ? 40c t a +125c 95 db output characteristics output voltage high v oh i l = 1 ma ; ?40c t a +125c 4.97 4.991 v output voltage low v ol i l = 1 ma ; ? 40c t a +125c 8 3 0 mv output current i out v out = 0.5 v 220 ma power supply power supp ly rejection ratio psrr v s = 2.7 v to 5.0 v 88 105 db supply current/amplifier i sy v o = 0 v 3 .7 4 .5 ma ?40c t a +125c 5.3 ma input capacitance c in differential 9. 3 pf common - mode 16.7 pf noise performance input voltage noise density e n f = 1 khz 4 nv/ hz f = 10 khz 2.7 nv/ hz total harmonic distortion + noise thd + n g = 1, r l = 1 k?, f = 1 khz, v in = 2 v p -p 0.000 7 % frequency response gain bandwidth product gbp 28 mhz slew rate sr r l = 10 k ? 1 1 v/s settling time ts to 0. 1% , v in = 0 v to 2 v step , g = +1 370 n s phase margin c l = 0 pf 69 degrees
ad8655 /ad8656 data sheet rev. d | page 4 of 20 v s = 2.7 v, v cm = v s /2, t a = 25c, unless otherwise specified. table 2 . parameter symbol conditions min typ max unit input characteristics offset voltage v os v cm = 0 v to 2.7 v 44 2 50 v ?40c t a +125c 550 v offset voltage drift ? v os / ? t ?40c t a +125c 0. 4 2.0 v/c input bias current i b 1 10 pa ?40c t a +125c 5 00 pa input offset current i os 10 pa ?40c t a +125c 5 00 pa input voltage range 0 2.7 v common - mode rejection ratio cmrr v cm = 0 v to 2.7 v 80 98 db large signal voltage gain a vo v o = 0.2 v to 2.5 v, r l = 10 k?, v cm = 0 v 98 db ? 40c t a +125c 90 db output characteristics output voltage high v oh i l = 1 ma ; ?40c t a +125c 2.6 7 2.688 v output voltage low v ol i l = 1 ma ; ?40c t a +125c 10 3 0 mv output current i out v out = 0.5 v 75 ma power supply power supply rejection ratio psrr v s = 2.7 v to 5.0 v 88 105 db supply current/amplifier i sy v o = 0 v 3.7 4.5 ma ?40c t a +125c 5.3 ma input capacitance c in differential 9. 3 pf common - mode 16.7 pf noise performance input voltage noise density e n f = 1 khz 4.0 nv/ hz f = 10 khz 2.7 nv/ hz total harmonic distortio n + noise thd + n g = 1, r l = 1 k?, f = 1 khz, v in = 2 v p -p 0.000 7 % frequency response gain bandwidth product gbp 27 mhz slew rate sr r l = 10 k? 8.5 v/s settling time ts to 0.1%, v in = 0 to 1 v step , g = +1 370 ns phase margin c l = 0 pf 54 degrees
data sheet ad8655 /ad8656 rev. d | page 5 of 20 absolute maximum rat ings table 3 . parameter rating supply voltage 6 v input voltage vss ? 0.3 v to vdd + 0.3 v differential input voltage 6 v output short - circuit duration to gnd indefinite electros tatic discharge (hbm) 3.0 kv storage temperature range r, rm packages ?65c to +150c junction temperature range r, rm packages ?65c to +150c lead temperature (soldering, 10 s ec ) 260 c stresses above those listed under absolute maximum ratings may cause permanent damage to the device. t his is a stress rating only; functional operation of the device at these or any other condition s above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rat ing conditions for extended periods may affect device reliability. table 4 . package type ja 1 jc unit 8 - lead msop (rm) 210 45 c/w 8 - lead soic (r) 158 43 c/w 1 ja is specified for worst - case conditions; that is, ja is specified for a device soldered in the circuit board for surface - mount packages. esd caution esd (electrostatic discharge) sensitive device. elect rostatic charges as high as 4000 v readily a ccumulate on the human body and test equipment and can discharge without detection. although this product features proprietary esd protection circuitry, permanent damage may occu r on devices subjected to high energy electrostatic discharges. therefore, proper esd precautions are recommended to avoid performance degradation or loss of functionality.
ad8655 /ad8656 data sheet rev. d | page 6 of 20 typical performance characteristics 60 50 40 30 20 10 0 ? 150 ? 100 ? 50 0 50 100 150 v os ( v) number of amplifiers 05304-001 v s = 2.5v figure 5 . input offset voltage distribution 150.0 100.0 50.0 0.0 ? 50.0 ? 100.0 ? 150.0 ? 50 0 50 temperature ( c) 100 150 v os ( v) 05304-002 v s = 2.5v figure 6 . input offset voltage vs. temperature 60 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 1.0 1.2 |tcv os | (v/c) 1.4 1.6 number of amplifiers 05304-003 v s = 2.5v figure 7 . |tcv os | distribution 20 10 0 ?10 ?20 ?30 0 1 2 3 4 common-mode voltage (v) 5 6 v os (v) 05304-004 v s = 2.5v figure 8 . input offset voltage vs. common - mode vo ltage 250 200 150 100 50 0 0 20 40 60 80 100 120 140 temperature ( c) ib (pa) v s = 2.5v 05304-005 figure 9 . input bias current vs. temperature 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 1 2 3 4 supply voltage (v) 5 6 supply current (ma) 05304-006 v s = 2.5v figure 10 . supply current vs. supply voltage
data sheet ad8655 /ad8656 rev. d | page 7 of 20 4.5 4.0 3.5 3.0 2.5 2.0 ? 50 0 50 temperature ( c) 100 150 supply current (ma) v s = 2.5v 05304-007 figure 11 . supply current vs. temperature v oh v ol 2500 2000 1500 1000 500 0 0 50 100 150 200 current load (ma) 250 delta swing from supply (mv) 05304-008 v s = 2.5v figure 12 . ad8655 output voltage to supply rail vs. current load 100 10 1 0.1 1 10 current load (ma) 100 1000 delta swing from supply (mv) 10000 1000 v s = 2.5v v ol v oh 05304-056 figure 13 . ad8656 output swing vs. current load 4.996 4.990 4.988 4.986 4.984 4.982 ? 50 0 50 temperature ( c) 100 150 v oh (v) 05304-009 4.992 4.994 v s = 2.5v load current = 1ma figure 14 . output voltage swing high vs. temperature 12 10 8 6 4 2 ? 50 0 50 temperature ( c) 100 150 v ol (mv) 05304-010 load current = 1ma v s = 2.5v figure 15 . output voltage swing low vs. temperature 80 60 0 100 1k 10k frequency (hz) 100k 10m cmrr (db) 120 100 v s = 2.5v v in = 28mv r l = 1m ? c l = 47pf 40 20 1m 05304-011 figure 16 . cmrr vs. frequency
ad8655 /ad8656 data sheet rev. d | page 8 of 20 110.00 107.00 104.00 101.00 98.00 95.00 92.00 ? 50 0 50 temperature ( c) 100 150 cmrr (db) 05304-012 v s = 2.5v v cm = 0v figure 17 . large signal cmrr vs. temperature 100 80 60 40 20 0 100 1k 10k 100k 1m frequency (hz) 10m 100m psrr (db) v s = 2.5v v in = 50mv r l = 1m ? c l = 47pf 05304-013 +psrr ? psrr figure 18 . small signal pssr vs. f requency 110.00 108.00 106.00 104.00 102.00 100.00 ? 50 0 50 temperature ( c) 100 150 psrr (db) 05304-014 v s = 2.5v figure 19 . large signal pssr vs. temperature 100 10 1 1 10 100 1k frequency (hz) 10k 100k voltage noise density (nv/ hz 1/2) 05304-019 v s = 2.5v figure 20 . voltage noise density vs. frequency 1 v s = 2.5v vn (p-p) = 1.23 v 05304-020 500nv/div 1s/div figure 21 . low frequency noise (0.1 hz to 10 hz). t 2 v s = 2.5v c l = 50pf gain = +1 05304-021 1v/div 20s/div v in v out figure 22 . no phase reversal
data sheet ad8655 /ad8656 rev. d | page 9 of 20 120 100 80 60 40 20 0 ? 20 ? 40 10k 100k 1m frequency (hz) 10m 100m gain (db) 05304-015 ? 90 ? 135 ? 180 ? 225 phase shift (degrees) ? 45 v s = 2.5v c load = 11.5pf phase margin = 69 figure 23 . open - loop gain and phase vs. frequency 140.00 130.00 120.00 110.00 90.00 ? 50 0 50 temperature ( c) 100 150 a vo (db) 05304-016 v s = 2.5v r l = 10k ? 100.00 figure 24 . large signal open - loop gain vs. temperature 40 50 30 20 1k 10k 100k 1m frequency (hz) 10m 100m closed-loop gain (db) 05304-017 v s = 2.5v r l = 1m? c l = 47pf 10 0 ?10 ?20 figure 25 . clos ed - loop gain vs. frequency 6 5 4 3 2 1 0 10k 100k 1m frequency (hz) 10m output (v) 05304-018 v s = 2.5v v i n = 5v g = +1 figure 26 . maximum output swing vs. frequency t 2 v s = 2.5v c l = 100pf gain = +1 v in = 4v 05304-022 time (10s/div) v out (1v/div) figure 27 . large signal response 2 t v s = 2.5v c l = 100pf g = +1 05304-023 time (1 s/div) v out (100mv/div) figure 28 . small signal response
ad8655 /ad8656 data sheet rev. d | page 10 of 20 30 25 20 15 10 5 0 0 50 100 150 200 250 300 350 capacitance (pf) overshoot % v s = 2.5v v in = 200mv ? os +os 05304-024 figure 29 . small signal overshoot vs. load capacitance t 2 1 v s = 2.5v v in = 300mv gain = ? 10 recovery time = 240ns 05304-025 300mv 0v 0v ? 2.5v v in v out 400ns/div figure 30 . negative overload recovery time 1 2 05304-026 400ns/div v s = 2.5v v in = 300mv gain = ?10 recovery time = 240ns t v in v out 0v 0v ?300mv 2.5v figure 31 . positive overload recovery time 100 10 1 0.1 frequency (hz) 100 1k 10k 100k 1m 10m 100m output impedance (?) 05304-027 v s = 2.5v g = +100 g = +10 g = +1 figure 32 . output im pedance vs. frequency 80 70 60 50 40 30 20 10 0 ? 150 ? 125 ? 100 ? 75 ? 50 ? 25 0 v os ( v) 25 50 75 100 125 150 number of amplifiers 05304-028 v s = 1.35v figure 33 . input offset voltage distribution 60 40 20 0 ? 20 ? 40 ? 50 0 50 100 150 temperature ( c) v os ( v) 05304-029 v s = 1.35v figure 34 . input offset voltage vs. temperature
data sheet ad8655 /ad8656 rev. d | page 11 of 20 80 70 60 50 40 30 20 10 0 0 0.2 0.4 0.6 0.8 |tcv os | ( v/ c) 1.0 1.2 1.4 1.6 number of amplifiers 05304-030 v s = 1.35v figure 35 . |tcv os | distribution 4.5 4.0 3.5 3.0 2.5 2.0 ? 50 0 50 100 150 temperature ( c) supply current (ma) 05304-031 v s = 1.35v figure 36 . supply current vs. temperature 1400 1200 1000 800 600 400 200 0 0 20 40 60 80 load current (ma) 100 120 (v sy -v out ) (mv) v s = 1.35v v oh v ol 05304-050 figure 37 . ad8655 output voltage to supply rail vs. load current 100 10 1 0.1 1 10 current load (ma) 100 delta output from supply (mv) 10000 1000 v ol v oh v s = 1.35v 05304-057 figure 38 . ad8656 output swing vs. current load 2.698 2.694 2.690 2.686 2.682 2.678 2.674 ? 50 0 50 100 150 temperature ( c) v oh (v) 05304-032 v s = 1.35v load current = 1ma figure 39 . output voltage swing high vs. temperature 14 12 10 8 6 4 2 ? 50 0 50 100 150 temperature ( c) v ol (mv) 05304-033 v s = 1.35v load current = 1ma figure 40 . output voltage swing low vs. temperature
ad8655 /ad8656 data sheet rev. d | page 12 of 20 t 2 v s = 1.35v g = +1 c l = 50pf 05304-047 1v/div v in v out 20s/div figure 41 . no phase reversal t 2 v s = 1.35v c l = 50pf gain = +1 05304-042 time (10 s/div) v out (500mv/div) figure 42 . large signal respons e 2 t v s = 1.35v c l = 100pf gain = +1 05304-043 time (1s/div) v out (100mv/div) figure 43 . small signal response 35 30 25 20 15 10 5 0 0 50 100 150 200 250 300 350 capacitance (pf) overshoot % v s = 1.35v v in = 200mv ? os +os 05304-044 figure 44 . small signal overshoot vs. load capacitance 400ns/div t 1 2 v s = 1.35v v in = 200mv gain = ?10 recovery time = 180ns 05304-045 200mv 0v 0v ?1.35v v in v out figure 45 . negative overload recovery time t 1 2 v s = 1.35v v in = 200mv gain = ?10 recovery time = 200ns 05304-046 0v ?200mv 1.35v 0v 400ns/div v in v out figure 46 . positive overload recovery time
data sheet ad8655 /ad8656 rev. d | page 13 of 20 40 20 0 100 1k 10k frequency (hz) 100k 1m cmrr (db) 120 80 100 60 v s = 1.35v v in = 28mv r l = 1m ? c l = 47pf 05304-034 figure 47 . cmrr vs. frequency 102.00 98.00 94.00 90.00 86.00 ? 50 0 50 temperature ( c) 100 150 cmrr (db) 05304-035 v s = 1.35v figure 48 . large signal cmrr vs. temperature 100 80 60 40 20 0 100 1k 10k 100k frequency (hz) 1m 100m 10m psrr (db) v s = 1.35v v in = 50mv r l = 1m ? c l = 47pf 05304-040 +psrr ? psrr figure 49 . small signal pssr vs. frequency 120 100 80 60 40 20 ?20 ?40 10k 100k 1m frequency (hz) 10m 100m gain (db) 05304-036 ?90 ?135 ?180 ?225 phase shift (degrees) ?45 v s = 1.35v c load = 11.5pf phase margin = 54 0 fi gure 50 . open - loop gain and phase vs. frequency 130.00 120.00 110.00 100.00 90.00 80.00 ? 50 0 50 temperature ( c) 100 150 a vo (db) 05304-037 v s = 1.35v r l = 10k ? figure 51 . large signal open - loop gain vs. temperature 50 40 30 20 10 0 ?10 ?20 1k 10k 100k 1m frequency (hz) 10m 100m closed-loop gain (db) v s = 1.35v r l = 1m? c l = 47pf 05304-038 figure 52 . closed - loop gain vs. frequency
ad8655 /ad8656 data sheet rev. d | page 14 of 20 3.0 2.5 2.0 1.5 1.0 0.5 0 10k 100k 1m frequency (hz) 10m output (v) 05304-039 v s = 1.35v v in = 2.7v g = +1 no load figure 53 . maximum output swing vs. frequency 1000 100 10 1 0.1 frequency (hz) 100 1k 10k 100k 1m 100m 10m output impedance (?) 05304-041 v s = 1.35v g = +1 g = +100 g = +10 figure 54 . output impedance vs. frequency ? 40 ? 60 ? 140 10 100 1k frequency (hz) 10k channel seperation (db) 0 ? 20 100k 1m 10m 100m ? 80 ? 100 ? 120 v s = 2.5v v in = 50mv v+ v ? +2.5v ? 2.5v + ? v in 50mv p-p a r2 100 ? r1 10k ? v ? v+ v out b 05304-058 figure 55 . channel separation vs. frequency
data sheet ad8655 /ad8656 rev. d | page 15 of 20 theory of operation the ad8655/ad8656 amplifier s are voltage feedback, rail - to - rail input and outp ut precision cmos amplifier s , which operate from 2.7 v to 5.0 v of power sup ply voltage. these amplifiers use the analog devices digitrim technology to achieve a higher degree of precision than is available fro m most cmos amplifiers. digitrim technology, used in a number of adi amplifiers, is a method of trimming the offset voltage of the amplifier after it is packag ed. the advantage of post - package trimming is that it corrects any offset voltages caused by the mechanical stresses of assembly. th e ad8655/ad8656 are available in standard op amp pinout s, making digitrim completely transparent to the user. the input stage of the amplifier s is a true rail - to - rail architecture, allowing the input common - mode voltage range of the amplifier s to extend to both positive and negative supply rails. the open - loop gain of the ad8655 /ad8656 with a load of 10 k? is typically 110 db. the ad8655/ad8656 can be used in any precision op amp application. the amplifier does not exhi bit phase reversal for common - mode voltages within the power supply. the ad8655/ad8656 are great choice s for high resolution data acquisition systems w i th voltage noise of 2.7 nv/hz and thd + noise of C 103 db for a 2 v p - p signal at 10 khz . their low noi se, sub - pa input bias current, precision offset, and high speed make them su perb preamp s for fast filter applications. the speed and output drive capability of the ad8655/ad8656 also make them useful in video applications.
ad8655 /ad8656 data sheet rev. d | page 16 of 20 applications input overvolta ge protection the internal protective cir cuitry of the ad8655/ad8656 allows voltages exceeding the sup ply to be applied at the input. it is recommended, however, not to apply voltages that exce ed the supplies by more than 0.3 v at either input of the ampl ifier. if a higher input voltage is applied, series resistors should be used to limit the current flowing into the inputs. the input current should be l imited to less than 5 ma. the extremely low input bias current allows the use of larger resistors, which allows the user to apply higher voltages at the inputs. the use of these resistors adds thermal noise, which contributes to the overall output voltage noise of the amplifier. for example, a 10 k ? resistor has less than 12.6 nv/hz of thermal noise and less than 10 nv of err or voltage at room temperature. input capacitance along with bypassing and ground, high speed amplifiers can be sensitive to parasitic capacitance between the inputs and groun d. for circuits with resistive feedback network, the total capacitance, whether it is the source capacitance, stray capacitance on the input pin , or the input capacitance of the amplifier , causes a breakpoint in the no i se gain of the circuit . a s a result, a capacitor must be added in parallel with the gain resistor to obtain stability. the noise gain is a function of frequency and pea ks at the higher frequencies, assuming the feedback capaci - tor is selected to make the second - order system critic ally damped. a few pico farads of capacitance at the input reduce the input impedance at high frequencies, which increase s the amplifiers gain, causing peaking in the frequency response or oscillations. with the ad8655/ad8656 , additional input damping is required for stability with capacitive loads greater than 2 00 pf with d irect input to output feedback. s ee the driving capacitive loads section. driving capacitive l oads although the ad8655/ad8656 can drive capacitive loads u p to 500 pf without oscillating, a large amount of ringing is present when operating the part with input frequencies above 100 khz. this is especially true when the amplifier s are configured in positive unity gain (worst case). when such large capacitive loa ds are required, the use of external compensation is highly recommended. this reduces the overshoot and minimizes ringing, which , in turn , improves the stability of the ad8655/ad8656 when driving large capacitive loads . one simple technique for compensat ion is a snubber that consists of a simple rc network. with this circuit in place, output swing is maintained, and the amplifier is stable at all gains. figure 57 shows the implementation of a snubber, which reduce s overshoot by more than 30% and eliminates ringi ng . using a snubber does not recover the loss of bandwidth incurred from a heavy capacitive load. time (2 s/div) v s = 2.5v a v = 1 c l = 500pf 05304-051 voltage (100mv/div) figure 56 . driving heavy capacitive loads without compensation +in 200? 500pf 500pf ?in v cc v ee 200mv + ? 05304-052 + ? figure 57 . snubber network v s = 2.5v a v = 1 r s = 200 ? c s = 500pf c l = 500pf time (10 s/div) 05304-053 voltage (100mv/div) figure 58 . driving heavy capacitive loads using a snubber network
data sheet ad8655 /ad8656 rev. d | page 17 of 20 thd readings vs. common - mode voltage tota l h armonic distortion of the ad8655/ad8656 is well below 0.0007% with a load of 1 k ?. this distortion is a function of the circuit configuration, the voltage applied, and the layout, in addit ion to other factors. + ? v in r l v out +2.5v ? 2.5v ad8655 05304-054 figure 59 . thd + n test circuit 1.0 0.1 0.01 0.001 0.0001 % 20 100 1k 10k 80k 50 500 5k 50k 200 2k 20k hz 0.5 0.05 0.005 0.0005 0.2 0.02 0.002 0.0002 sweep 1: v in = 2v p-p r l = 10k? sweep 2: v in = 2v p-p r l = 1k? sweep 1 sweep 2 05304-055 figure 60 . thd + noise vs. f requency
ad8655 /ad8656 data sheet rev. d | page 18 of 20 layout, grounding, a nd bypassing conside rations power supply bypassi ng power supply pins can act as inputs for noise, so care must be taken to apply a noise - fr ee, stable dc voltage . the purpose of bypass capacitors is to create low impedances from the supply to ground at all frequencies, thereby shunting or filtering most of the noise. bypassing schemes are designed to minimize the supply impedance at all frequencies with a parallel combination of capacitors with values of 0.1 f and 4.7 f. chip capac itors of 0.1 f (x7r or npo) are critical and should be as close as possible to the amplifier package. the 4.7 f tantalum capacitor is less critical for high frequency bypassing, and, in most cases, only one is needed per board at the supply inputs. gro unding a ground plane layer is important for densely packed pc boards to minimize parasitic inductances. this minimize s voltage drops with changes in current . however, an under - standing of where the current flows in a circuit is critical to implementing e ffective high speed circuit design. the length of the current path is directly proportional to the magnitude of parasitic inductances , and, therefore, the high frequency i mpedance of the path. large changes in currents in an inductive ground return create unwanted voltage noise. the length of the high frequency bypa ss capacitor leads is c ritical, and, therefore, surface - mount capacitors are recom - mended. a parasitic inducta nce in the bypass ground trace work s against the low impedance created by the bypass ca pacitor. because load currents flow from the supplies, the ground for the load impedance should be at the same physical location as the bypass capacitor grounds. for larger value capacitors intended to be effective at lower frequencies, the current retu rn path distance is less critical. leakage currents poor pc board layout, contaminants, and the board insulator material can create leakage currents that are much larger than the input bias current of the ad8655/ad8656 . any voltage differential between the inputs and nearby t races creates leakage currents through the pc board insulator, for example, 1 v/100 g ? = 10 pa. similarly, any contaminants on the board can create significant leakage (skin oils are a common problem). to significantly reduce leakag e , put a guard ring (shield) around the inputs and input leads that are driven to the same voltage potential as the inputs. this ensures there is no voltage potential between the inputs an d the surrounding area to create any leakage currents. to be effecti ve, the guard ring must be driven by a relatively low impedance source and should completely surround the input leads on all sides, above and below, by using a multilayer board. the charge absorption of the insulator material itself can also cause leakage currents . minimizing the amount of material between the inp ut leads and the guard ring help s to reduce the absorption. also, using low absorption materials, such as teflon? or ceramic, may be necessary in some instances.
data sheet ad8655 /ad8656 rev. d | page 19 of 20 outline dimensions c o n t r o l l i n g d i m e n s i o n s a r e i n m i l l i m e t e r s ; i n c h d i m e n s i o n s ( i n p a r e n t h e s e s ) a r e r o u n d e d - o f f m i l l i m e t e r e q u i v a l e n t s f o r r e f e r e n c e o n l y a n d a r e n o t a p p r o p r i a t e f o r u s e i n d e s i g n . c o m p l i a n t t o j e d e c s t a n d a r d s m s - 0 1 2 - a a 0 1 2 4 0 7 - a 0 . 2 5 ( 0 . 0 0 9 8 ) 0 . 1 7 ( 0 . 0 0 6 7 ) 1 . 2 7 ( 0 . 0 5 0 0 ) 0 . 4 0 ( 0 . 0 1 5 7 ) 0 . 5 0 ( 0 . 0 1 9 6 ) 0 . 2 5 ( 0 . 0 0 9 9 ) 4 5 8 0 1 . 7 5 ( 0 . 0 6 8 8 ) 1 . 3 5 ( 0 . 0 5 3 2 ) s e a t i n g p l a n e 0 . 2 5 ( 0 . 0 0 9 8 ) 0 . 1 0 ( 0 . 0 0 4 0 ) 4 1 8 5 5 . 0 0 ( 0 . 1 9 6 8 ) 4 . 8 0 ( 0 . 1 8 9 0 ) 4 . 0 0 ( 0 . 1 5 7 4 ) 3 . 8 0 ( 0 . 1 4 9 7 ) 1 . 2 7 ( 0 . 0 5 0 0 ) b s c 6 . 2 0 ( 0 . 2 4 4 1 ) 5 . 8 0 ( 0 . 2 2 8 4 ) 0 . 5 1 ( 0 . 0 2 0 1 ) 0 . 3 1 ( 0 . 0 1 2 2 ) c o p l a n a r i t y 0 . 1 0 compliant to jedec standards mo-187-aa 6 0 0.80 0.55 0.40 4 8 1 5 0.65 bsc 0.40 0.25 1.10 max 3.20 3.00 2.80 coplanarity 0.10 0.23 0.09 3.20 3.00 2.80 5.15 4.90 4.65 pin 1 identifier 15 max 0.95 0.85 0.75 0.15 0.05 10-07-2009-b figure 61 . 8 - lead standard small outline package [soic_n] narrow body (r - 8) dimensions shown in millimeters and (inches) figure 62 . 8 - lead mini small outline package [msop] (rm - 8) dimensions shown in millimeters ordering guide model 1 , 2 temperature range package description package option branding ad8655arz ?40c to +125c 8 - lead soic_n r -8 ad8655arz - reel ?40c to +125c 8 - lead soic_n r -8 ad8655arz - reel7 ?40c to +125c 8 - lead soic_n r -8 ad8655armz - reel ?4 0c to +125c 8 - lead msop rm -8 a 0 d ad8655armz ?40c to +125c 8 - lead msop rm -8 a0d ad8656arz ?40c to +125c 8 - lead soic_n r -8 ad8656arz - reel ?40c to +125c 8 - lead soic_n r -8 ad8656arz - reel7 ?40c to +125c 8 - lead soic_n r - 8 AD8656ARMZ ?40c to +1 25c 8 - lead msop rm -8 a0s AD8656ARMZ - reel ?40c to +125c 8 - lead msop rm -8 a0s ad8656warmz - reel ?40c to +125c 8 - lead msop rm -8 a0s 1 z = rohs compliant part. 2 w = qualified for automotive applications. automotive products the ad8656w model is available with controlled manufacturing to support the quality and reliability requirements of automotive applications. note that these automotive models may have specifications that differ from the commercial models; therefore, de signers should review the specifications section of this data sheet carefully . only the automotive grade product shown is available for use in automotive applications. co ntact your local analog devices account representative for specific product ordering information and to obtain the specific automotive reliability reports for th i s model . .
ad8655 /ad8656 data sheet rev. d | page 20 of 20 notes ? 2005 C 2013 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d0 5304 - 0 - 6/13(d)

▲Up To Search▲

Price & Availability of AD8656ARMZ

	To Download AD8656ARMZ Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .