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zero-drift, single-supply, rail-to-rail input/output operational amplifier ad8628/ad8629/AD8630 rev. e 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 chan ge without notice. no license is granted by implication or otherwise under any patent or patent ri ghts 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 ? 2005 analog devices, inc. all rights reserved. features lowest auto-zero amplifier noise low offset voltage: 1 v input offset drift: 0.002 v/c rail-to-rail input and output swing 5 v single-supply operation high gain, cmrr, and psrr: 120 db very low input bias current: 100 pa max low supply current: 1.0 ma overload recovery time: 10 s no external components required applications automotive sensors pressure and position sensors strain gage amplifiers medical instrumentation thermocouple amplifiers precision current sensing photodiode amplifier pin configurations out 1 v? 2 +in 3 v+ 5 ?in 4 ad8628 top view (not to scale) 02735-001 figure 1. 5-lead tsot (uj-5) and 5-lead sot-23 (rt-5) nc 1 ?in 2 +in 3 v? 4 nc 8 v+ 7 out 6 nc 5 nc = no connect ad8628 top view (not to scale) 02735-002 figure 2. 8-lead soic_n (r-8) out a 1 ?in a 2 +in a 3 v? 4 v+ 8 out b 7 ?in b 6 +in b 5 ad8629 top view (not to scale) 02735-063 figure 3. 8-lead soic_n (r-8) o ut a 1 ?in a 2 +in a 3 v? 4 v+ 8 out b 7 ?in b 6 +in b 5 ad8629 top view (not to scale) 02735-064 figure 4. 8-lead msop (rm-8) 02735-066 1 2 3 4 5 6 7 AD8630 ?in a +in a v+ out b ?in b +in b out a 14 13 12 11 10 9 8 ?in d +in d v? out c ?in c +in c out d top view (not to scale) figure 5. 14-lead soic_n (r-14) out a 1 ?in a 2 +in a 3 v+ 4 out d 14 ?in d 13 +in d 12 v? 11 +in b 5 +in c 10 ?in b 6 ?in c 9 out b 7 out c 8 AD8630 top view (not to scale) 02735-065 figure 6. 14-lead tssop (ru-14)
ad8628/ad8629/AD8630 rev. e | page 2 of 24 table of contents general description ......................................................................... 3 specifications ..................................................................................... 4 electrical characteristics v s = 5.0 v ............................................. 4 electrical characteristics v s = 2.7 v ............................................. 5 absolute maximum ratings ............................................................ 6 esd caution .................................................................................. 6 typical performance characteristics ............................................. 7 functional description .................................................................. 15 1/f noise ....................................................................................... 15 peak-to-peak noise .................................................................... 16 noise behavior with first-order low-pass filter .................. 16 total integrated input-referred noise for first-order filter .................................................................. 16 input overvoltage protection ................................................... 17 output phase reversal ............................................................... 17 overload recovery time .......................................................... 17 infrared sensors .......................................................................... 18 precision current shunt sensor ............................................... 19 output amplifier for high precision dacs ........................... 19 outline dimensions ....................................................................... 20 ordering guide .......................................................................... 22 revision history 5/05rev. d to rev. e changes to ordering guide .......................................................... 22 1/05rev. c to rev. d added AD8630 ...................................................................universal added figure 5 and figure 6........................................................... 1 changes to caption in figure 8 and figure 9 ............................... 7 changes to caption in figure 14 .................................................... 8 changes to figure 17........................................................................ 8 changes to figure 23 and figure 24............................................... 9 changes to figure 25 and figure 26............................................. 10 changes to figure 31...................................................................... 11 changes to figure 40, figure 41, figure 42................................. 12 changes to figure 43 and figure 44............................................. 13 changes to figure 51...................................................................... 15 updated outline dimensions ....................................................... 20 changes to ordering guide .......................................................... 22 10/04rev. b to rev. c updated formatting ...........................................................universal added ad8629 ...................................................................universal added soic and msop pin configurations ............................... 1 added figure 48.............................................................................. 13 changes to figure 62...................................................................... 17 added msop package ................................................................... 19 changes to ordering guide .......................................................... 22 10/03rev. a to rev. b changes to general description .....................................................1 changes to absolute maximum ratings........................................4 changes to ordering guide .............................................................4 added tsot-23 package .............................................................. 15 6/03rev. 0 to rev. a changes to specifications.................................................................3 changes to ordering guide .............................................................4 change to functional description............................................... 10 updated outline dimensions....................................................... 15 10/02revision 0: initial version
ad8628/ad8629/AD8630 rev. e | page 3 of 24 general description this amplifier has ultralow offset, drift, and bias current. the ad8628/ad8629/AD8630 are wide bandwidth auto-zero amplifiers featuring rail-to-rail input and output swings and low noise. operation is fully specified from 2.7 v to 5 v single supply (1.35 v to 2.5 v dual supply). the ad8628/ad8629/AD8630 provide benefits previously found only in expensive auto-zeroing or chopper-stabilized amplifiers. using analog devices topology, these zero-drift amplifiers combine low cost with high accuracy and low noise. no external capacitor is required. in addition, the ad8628/ ad8629/AD8630 greatly reduce the digital switching noise found in most chopper-stabilized amplifiers. with an offset voltage of only 1 v, drift of less than 0.005 v/c, and noise of only 0.5 v p-p (0 hz to 10 hz), the ad8628/ad8629/AD8630 are suited for applications in which error sources cannot be tolerated. position and pressure sensors, medical equipment, and strain gage amplifiers benefit greatly from nearly zero drift over their operating temperature range. many systems can take advantage of the rail-to-rail input and output swings provided by the ad8628/ad8629/AD8630 to reduce input biasing complexity and maximize snr. the ad8628/ad8629/AD8630 are specified for the extended industrial temperature range (?40c to +125c). the ad8628 is available in tiny tsot-23, sot-23, and the 8-lead narrow soic plastic packages. the ad8629 is available in the standard 8-lead narrow soic and msop plastic packages. the AD8630 quad amplifier is available in 14-lead narrow soic and tssop plastic packages.
ad8628/ad8629/AD8630 rev. e | page 4 of 24 specifications electrical characteristics v s = 5.0 v v s = 5.0 v, v cm = 2.5 v, t a = 25c, unless otherwise noted. table 1. parameter symbol conditions min typ max unit input characteristics offset voltage v os 1 5 v ?40c t a +125c 10 v input bias current i b 30 100 pa (AD8630) 100 300 pa ?40c t a +125c 1.5 na input offset current i os 50 200 pa ?40c t a +125c 250 pa input voltage range 0 5 v common-mode rejection ratio cmrr v cm = 0 v to 5 v 120 140 db ?40c t a +125c 115 130 db large signal voltage gain 1 a vo r l = 10 k, v o = 0.3 v to 4.7 v 125 145 db ?40c t a +125c 120 135 db offset voltage drift ?v os /?t ?40c t a +125c 0.002 0.02 v/c output characteristics output voltage high v oh r l = 100 k to ground 4.99 4.996 v ?40c t a +125c 4.99 4.995 v r l = 10 k to ground 4.95 4.98 v ?40c t a +125c 4.95 4.97 v output voltage low v ol r l = 100 k to v+ 1 5 mv ?40c t a +125c 2 5 mv r l = 10 k to v+ 10 20 mv ?40c t a +125c 15 20 mv short-circuit limit i sc 25 50 ma ?40c t a +125c 40 ma output current i o 30 ma ?40c t a +125c 15 ma power supply power supply rejection ratio psrr v s = 2.7 v to 5.5 v ?40c t a +125c 115 130 db supply current/amplifier i sy v o = 0 v 0.85 1.1 ma ?40c t a +125c 1.0 1.2 ma input capacitance differential c in 1.5 pf common-mode 8.0 pf dynamic performance slew rate sr r l = 10 k 1.0 v/s overload recovery time 0.05 ms gain bandwidth product gbp 2.5 mhz noise performance voltage noise e n p-p 0.1 hz to 10 hz 0.5 v p-p e n p-p 0.1 hz to 1.0 hz 0.16 v p-p voltage noise density e n f = 1 khz 22 nv/hz current noise density i n f = 10 hz 5 fa/hz 1 gain testing is highly dependent on test bandwidth.
ad8628/ad8629/AD8630 rev. e | page 5 of 24 electrical characteristics v s = 2.7 v v s = 2.7 v, v cm = 1.35 v, v o = 1.4 v, t a = 25c, unless otherwise noted. table 2. parameter symbol conditions min typ max unit input characteristics offset voltage v os 1 5 v ?40c t a +125c 10 v input bias current i b 30 100 pa (AD8630) 100 300 pa ?40c t a +125c 1.0 1.5 na input offset current i os 50 200 pa ?40c t a +125c 250 pa input voltage range 0 2.7 v common-mode rejection ratio cmrr v cm = 0 v to 2.7 v 115 130 db ?40c t a +125c 110 120 db large signal voltage gain 1 a vo r l = 10 k, v o = 0.3 v to 2.4 v 110 140 db ?40c t a +125c 105 130 db offset voltage drift ?v os /?t ?40c t a +125c 0.002 0.02 v/c output characteristics output voltage high v oh r l = 100 k to ground 2.68 2.695 v ?40c t a +125c 2.68 2.695 v r l = 10 k to ground 2.67 2.68 v ?40c t a +125c 2.67 2.675 v output voltage low v ol r l = 100 k to v+ 1 5 mv ?40c t a +125c 2 5 mv r l = 10 k to v+ 10 20 mv ?40c t a +125c 15 20 mv short-circuit limit i sc 10 15 ma ?40c t a +125c 10 ma output current i o 10 ma ?40c t a +125c 5 ma power supply power supply rejection ratio psrr v s = 2.7 v to 5.5 v ?40c t a +125c 115 130 db supply current/amplifier i sy v o = 0 v 0.75 1.0 ma ?40c t a +125c 0.9 1.2 ma input capacitance differential c in 1.5 pf common-mode 8.0 pf dynamic performance slew rate sr r l = 10 k 1 v/s overload recovery time 0.05 ms gain bandwidth product gbp 2 mhz noise performance voltage noise e n p-p 0.1 hz to 10 hz 0.5 v p-p voltage noise density e n f = 1 khz 22 nv/hz current noise density i n f = 10 hz 5 fa/hz 1 gain testing is highly dependent on test bandwidth.
ad8628/ad8629/AD8630 rev. e | page 6 of 24 absolute maximum ratings table 3. parameters ratings 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 indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. supply voltage 6 v input voltage gnd ? 0.3 v to v + 0.3 v s? differential input voltage 5.0 v 1 output short-circuit durati on to gnd indefinite storage temperature range r, rm, ru, rt, uj pack ages ?65c to +150c operating temperature range ?40c to +125c table 4. thermal characteristics junction temperature range r, rm, ru, rt, uj pack ages ?65c to +150c package type unit 1 ja jc lead temperature range (soldering, 60 sec) 300c 5-lead tsot-23 (uj-5) 207 61 c/w 1 differential input voltage is limited to 5 v or the supply voltage, whichever is less. 5-lead sot-23 (rt-5) 230 146 c/w 8-lead soic_n (r-8) 158 43 c/w 8-lead msop (rm-8) 190 44 c/w 14-lead soic_n (r-14) 105 43 c/w 14-lead tssop (ru-14) 148 23 c/w 1 ja is specified for worst-case conditions, that is, ja is specified for the device soldered in a circuit board for surf ace-mount packages. this was measured using a standard 2-layer board. esd caution esd (electrostatic discharge) sensitive device. electros tatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge wi thout 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.
ad8628/ad8629/AD8630 rev. e | page 7 of 24 typical performance characteristics input offset voltage ( v) number of amplifiers 180 160 140 120 100 80 60 40 20 0 ?2.5 ?1.5 ?0.5 0.5 1.5 2.5 02735-003 v s = 2.7v t a = 25 c input offset voltage ( v) number of amplifiers 100 80 90 60 70 40 50 10 20 30 0 ?2.5 ?1.5 ?0.5 0.5 1.5 2.5 02735-006 v s = 5v v cm = 2.5v t a = 25 c figure 7. input offset voltage distribution figure 10. input offset voltage distribution v s = 5v t a = ?40 c to +125 c tcvos (nv/ c) number of amplifiers 7 6 5 4 3 2 1 0 0 2 4 68 10 02735-007 +85c +25 c ?40 c v s = 5v input common-mode voltage (v) input bias current (pa) 60 40 50 30 10 20 0 012345 02735-004 6 figure 11. input offset voltage drift figure 8. ad8628 input bias current vs. input common-mode v s = 5v t a = 25 c source sink load current (ma) output voltage (mv) 1k 100 10 1 0.1 0.01 0.0001 0.001 0.1 0.01 1 10 02735-008 150c 125c input common-mode voltage (v) input bias current (pa) 1500 500 1000 0 ?1000 ?500 ?1500 012345 02735-005 6 v s = 5v figure 12. output voltage to supply rail vs. load current figure 9. ad8628 input bias current vs. input common-mode voltage at 5 v
ad8628/ad8629/AD8630 rev. e | page 8 of 24 v s = 2.7v source sink load current (ma) output voltage (mv) 1k 100 10 1 0.1 0.01 0.0001 0.001 0.1 0.01 1 10 02735-009 t a = 25 c supply voltage (v) supply current ( a) 1000 800 600 400 200 0 012 45 36 02735-012 figure 13. output voltage to supply rail vs. load current figure 16. supply current vs. supply voltage v s = 5v v cm = 2.5v t a = ?40 c to +150 c temperature ( c) input bias current (pa) 1500 1150 900 450 100 0 ?50 0 25 ?25 50 75 100 125 150 175 02735-010 frequency (hz) open-loop gain (db) 60 40 20 0 10k 100k 1m 10m 02735-013 45 90 135 180 225 0 phase shift (degrees) v s = 2.7v c l = 20pf r l = m = 45 figure 14. ad8628 input bias current vs. temperature figure 17. open-loop gain and phase vs. frequency t a = 25 c 5v 2.7v temperature ( c ) supply current ( a) 1250 1000 750 500 250 0 ?50 0 50 150 100 200 02735-011 v s = 5v c l = 20pf r l = m = 52.1 frequency (hz) open-loop gain (db) 70 60 50 40 30 20 0 ?10 ?20 10 ?30 10k 100k 1m 10m 02735-014 45 90 135 180 225 0 phase shift (degrees) figure 18. open-loop gain and phase vs. frequency figure 15. supply current vs. temperature
ad8628/ad8629/AD8630 rev. e | page 9 of 24 frequency (hz) closed-loop gain (db) 70 60 50 40 30 20 0 ?10 ?20 10 ?30 1k 10k 100k 1m 10m 02735-015 v s = 2.7v c l = 20pf r l = 2k a v = 100 a v = 10 a v = 1 frequency (hz) output impedance ( ) 300 270 240 210 180 150 90 60 30 120 0 100 1k 10k 100k 1m 10m 100m 02735-018 v s = 5v a v = 100 a v = 10 a v = 1 figure 19. closed-loop gain vs. frequency figure 22. output impedance vs. frequency frequency (hz) closed-loop gain (db) 70 60 50 40 30 20 0 ?10 ?20 10 ?30 1k 10k 100k 1m 10m 02735-016 v s = 5v c l = 20pf r l = 2k a v = 100 a v = 10 a v = 1 v s = 1.35v c l = 300pf r l = a v = 1 time (4 s/div) voltage (500mv/div) 02735-019 0v figure 23. large signal transient response figure 20. closed-loop gain vs. frequency frequency (hz) output impedance ( ) 300 270 240 210 180 150 90 60 30 120 0 100 1k 10k 100k 1m 10m 100m 02735-017 v s = 2.7v a v = 100 a v = 10 a v = 1 v s = 2.5v c l = 300pf r l = a v = 1 time (5 s/div) voltage (1v/div) 0v 02735-020 figure 24. large signal transient response figure 21. output impedance vs. frequency
ad8628/ad8629/AD8630 rev. e | page 10 of 24 capacitive load (pf) overshoot (%) 80 70 60 50 30 20 10 40 0 1 10 100 1k 02735-024 v s = 2.5v r l = 2k t a = 25 c os? os+ v s = 1.35v c l = 50pf r l = a v = 1 time (4 s/div) voltage (50mv/div) 0v 02735-021 figure 25. small signal transient response figure 28. small signal overshoot vs. load capacitance v s = 2.5v c l = 50pf r l = a v = 1 time (4 s/div) voltage (50mv/div) 0v 02735-022 time (2 s/div) voltage (v) v out 0v 0v v in 02735-025 v s = 2.5v a v = ?50 r l = 10k c l = 0 ch1 = 50mv/div ch2 = 1v/div figure 26. small signal transient response figure 29. positive overvoltage recovery time (10 s/div) voltage (v) v out 0v 0v v in 02735-026 v s = 2.5v a v = ?50 r l = 10k c l = 0 ch1 = 50mv/div ch2 = 1v/div capacitive load (pf) overshoot (%) 100 90 80 70 60 50 30 20 10 40 0 1 10 100 1k 02735-023 v s = 1.35v r l = 2k t a = 25 c os? os+ figure 27. small signal overshoot vs. load capacitance figure 30. negative overvoltage recovery
ad8628/ad8629/AD8630 rev. e | page 11 of 24 frequency (hz) psrr (db) 140 120 100 80 60 40 0 ?20 ?40 20 ?60 100 1k 10k 100k 1m 10m 02735-030 v s = 1.35v +psrr ?psrr time (200 s/div) voltage (1v/div) 0v 02735-027 v s = 2.5v v in = 1khz @ 3v p-p c l = 0pf r l = 10k a v = 1 figure 34. psrr vs. frequency figure 31. no phase reversal frequency (hz) psrr (db) 140 120 100 80 60 40 0 ?20 ?40 20 ?60 100 1k 10k 100k 1m 10m 02735-031 v s = 2.5v +psrr ?psrr frequency (hz) cmrr (db) 140 120 100 80 60 40 0 ?20 ?40 20 ?60 100 1k 10k 100k 1m 10m 02735-028 v s = 2.7v figure 35. psrr vs. frequency figure 32. cmrr vs. frequency frequency (hz) cmrr (db) 140 120 100 80 60 40 0 ?20 ?40 20 ?60 100 1k 10k 100k 1m 10m 02735-029 v s = 5v frequency (hz) output swing (v p-p) 3.0 2.5 2.0 1.5 1.0 0.5 0 100 1k 10k 100k 1m 02735-032 v s = 2.7v r l = 10k t a = 25 c a v = 1 figure 36. maximum output swing vs. frequency figure 33. cmrr vs. frequency
ad8628/ad8629/AD8630 rev. e | page 12 of 24 frequency (hz) output swing (v p-p) 5.5 2.5 3.0 3.5 4.0 4.5 5.0 2.0 1.5 1.0 0.5 0 100 1k 10k 100k 1m 02735-033 v s = 5v r l = 10k t a = 25c a v = 1 frequency (khz) voltage noise density (nv/ hz) 120 105 90 75 45 30 15 60 0 0 0.5 1.0 1.5 2.0 2.5 02735-036 v s = 2.7v noise at 1khz = 21.3nv figure 37. maximum output swing vs. frequency figure 40. voltage noise density at 2.7 v from 0 hz to 2.5 khz time ( s) voltage ( v) 0.60 0.45 0.30 0.15 ?0.15 ?0.30 ?0.45 0 ?0.60 01 23 45678910 02735-034 v s = 2.7v frequency (khz) voltage noise density (nv/ hz) 120 105 90 75 45 30 15 60 0 0 5 10 15 20 25 02735-037 v s = 2.7v noise at 10khz = 42.4nv figure 41. voltage noise density at 2.7 v from 0 hz to 25 khz figure 38. 0.1 hz to 10 hz noise time ( s) voltage ( v) 0.60 0.45 0.30 0.15 ?0.15 ?0.30 ?0.45 0 ?0.60 01 23 45678910 02735-035 v s = 5v frequency (khz) voltage noise density (nv/ hz) 120 105 90 75 45 30 15 60 0 0 0.5 1.0 1.5 2.0 2.5 02735-038 v s = 5v noise at 1khz = 22.1nv figure 39. 0.1 hz to 10 hz noise figure 42. voltage noise density at 5 v from 0 hz to 2.5 khz
ad8628/ad8629/AD8630 rev. e | page 13 of 24 frequency (khz) voltage noise density (nv/ hz) 120 105 90 75 45 30 15 60 0 0 5 10 15 20 25 02735-039 v s = 5v noise at 10khz = 36.4nv temperature ( c) output short-circuit current (ma) 150 100 50 0 ?50 ?100 ?50 25 50 75 0?25 100 125 150 175 02735-042 v s = 2.7v t a = ?40 c to +150 c i sc ? i sc + figure 43. voltage noise density at 5 v from 0 hz to 25 khz figure 46. output short-circuit current vs. temperature frequency (khz) voltage noise density (nv/ hz) 120 105 90 75 45 30 15 60 0 05 02735-040 1 0 v s = 5v temperature ( c) output short-circuit current (ma) 150 100 50 0 ?50 ?100 ?50 25 50 75 0?25 100 125 150 175 02735-043 v s = 5v t a = ?40 c to +150 c i sc ? i sc + figure 44. voltage noise figure 47. output short-circuit current vs. temperature temperature ( c) output-to-rail voltage (mv) 1k 100 10 1 0.10 ?50 25 50 75 0?25 100 125 150 175 02735-044 v s = 5v v cc ? v oh @ 1k v cc ? v oh @ 10k v cc ? v oh @ 100k v ol ? v ee @ 1k v ol ? v ee @ 10k v ol ? v ee @ 100k v s = 2.7v to 5v t a = ?40 c to +125 c temperature ( c) power supply rejection (db) 150 130 120 140 110 100 90 60 70 80 50 ?50 0 25 ?25 50 75 100 125 02735-041 figure 48. output-to-rail voltage vs. temperature figure 45. power supply rejection vs. temperature
ad8628/ad8629/AD8630 rev. e | page 14 of 24 frequency (hz) channel separation (db) 140 120 100 80 60 40 20 0 1k 10k 100k 1m 10m 02735-062 v out v in 28mv p-p ?2.5v +2.5v r1 10k v? v+ ? + v+ v? ab r2 100 v sy = 2.5v temperature ( c) output-to-rail voltage (mv) 1k 100 10 1 0.10 ?50 25 50 75 0?25 100 125 150 175 02735-045 v s = 2.7v v cc ? v oh @ 1k v cc ? v oh @ 10k v cc ? v oh @ 100k v ol ? v ee @ 1k v ol ? v ee @ 10k v ol ? v ee @ 100k figure 50. ad8629/AD8630 channel separation figure 49. output-to-rail voltage vs. temperature
ad8628/ad8629/AD8630 rev. e | page 15 of 24 functional description 1/f noise the ad8628/ad8629/AD8630 are single-supply, ultrahigh precision rail-to-rail input and output operational amplifiers. the typical offset voltage of less than 1 v allows these amplifi- ers to be easily configured for high gains without risk of excessive output voltage errors. the extremely small tempera- ture drift of 2 nv/c ensures a minimum of offset voltage error over their entire temperature range of ?40c to +125c, making these amplifiers ideal for a variety of sensitive measurement applications in harsh operating environments. 1/f noise, also known as pink noise, is a major contributor to errors in dc-coupled measurements. this 1/f noise error term can be in the range of several v or more, and, when amplified with the closed-loop gain of the circuit, can show up as a large output offset. for example, when an amplifier with a 5 v p-p 1/f noise is configured for a gain of 1,000, its output has 5 mv of error due to the 1/f noise. but the ad8628/ad8629/AD8630 eliminate 1/f noise internally, and thereby greatly reduce output errors. the ad8628/ad8629/AD8630 achieve a high degree of preci- sion through a patented combination of auto-zeroing and chopping. this unique topology allows the ad8628/ad8629/ AD8630 to maintain their low offset voltage over a wide temperature range and over their operating lifetime. the ad8628/ad8629/AD8630 also optimize the noise and band- width over previous generations of auto-zero amplifiers, offering the lowest voltage noise of any auto-zero amplifier by more than 50%. the internal elimination of 1/f noise is accomplished as follows. 1/f noise appears as a slowly varying offset to ad8628/ad8629/ AD8630 inputs. auto-zeroing corrects any dc or low frequency offset. therefore, the 1/f noise component is essentially removed, leaving the ad8628/ad8629/AD8630 free of 1/f noise. one of the biggest advantages that the ad8628/ad8629/ AD8630 bring to systems applications over competitive auto- zero amplifiers is their very low noise. the comparison shown in previous designs used either auto-zeroing or chopping to add precision to the specifications of an amplifier. auto-zeroing results in low noise energy at the auto-zeroing frequency, at the expense of higher low frequency noise due to aliasing of wide- band noise into the auto-zeroed frequency band. chopping results in lower low frequency noise at the expense of larger noise energy at the chopping frequency. the ad8628/ad8629/ AD8630 family uses both auto-zeroing and chopping in a patented ping-pong arrangement to obtain lower low frequency noise together with lower energy at the chopping and auto- zeroing frequencies, maximizing the signal-to-noise ratio (snr) for the majority of applications without the need for additional filtering. the relatively high clock frequency of 15 khz simplifies filter requirements for a wide, useful, noise-free bandwidth. figure 51 indicates an input-referred noise density of 19.4 nv/hz at 1 khz for the ad8628, which is much better than the ltc2050 and lmc2001. the noise is flat from dc to 1.5 khz, slowly increasing up to 20 khz. the lower noise at low frequency is desirable where auto-zero amplifiers are widely used. mk at 1khz for all 3 graphs frequency (khz) voltage noise density (nv/ hz) 120 105 90 75 60 45 30 15 0 04 28 61 02735-046 0 1 2 ltc2050 (89.7nv/ hz) lmc2001 (31.1nv/ hz) ad8628 (19.4nv/ hz) the ad8628 is among the few auto-zero amplifiers offered in the 5-lead tsot-23 package. this provides a significant improvement over the ac parameters of the previous auto-zero amplifiers. the ad8628/ad8629/AD8630 have low noise over a relatively wide bandwidth (0 hz to 10 khz) and can be used where the highest dc precision is required. in systems with signal bandwidths of from 5 khz to 10 khz, the ad8628/ ad8629/AD8630 provide true 16-bit accuracy, making them the best choice for very high resolution systems. figure 51. noise spectral density of ad8628 vs. competition
ad8628/ad8629/AD8630 rev. e | page 16 of 24 frequency (khz) noise (db) 50 45 40 35 30 25 15 10 5 20 0 0 30 60 100908070 5040 2010 02735-050 peak-to-peak noise because of the ping-pong action between auto-zeroing and chopping, the peak-to-peak noise of the ad8628/ad8629/AD8630 is much lower than the competition. figure 52 and figure 53 show this comparison. e n p-p = 0.5 v bw = 0.1hz to 10hz time (1s/div) voltage (0.5 v/div) 02735-047 figure 55. simulation transfer function of the test circuit frequency (khz) noise (db) 50 45 40 35 30 25 15 10 5 20 0 0 30 60 100908070 5040 2010 02735-051 figure 52. ad8628 peak-to-peak noise e n p-p = 2.3 v bw = 0.1hz to 10hz time (1s/div) voltage (0.5 v/div) 02735-048 figure 56. actual transfer function of the test circuit the measured noise spectrum of the test circuit charted in figure 56 shows that noise between 5 khz and 45 khz is successfully rolled off by the first-order filter. total integrated input-referred noise for first-order filter figure 53. ltc2050 peak-to-peak noise noise behavior with first-order low-pass filter for a first-order filter, the total integrated noise from the ad8628 is lower than the ltc2050. the ad8628 was simulated as a low-pass filter ( figure 55 ) and then configured as shown in 3db filter bandwidth (hz) rms noise ( v) 10 1 0.1 10 100 10k 1k 02735-052 ltc2050 ad8551 ad8628 figure 54 . the behavior of the ad8628 matches the simulated data. it was verified that noise is rolled off by first-order filtering. figure 55 and figure 56 show the difference between the simulated and actual transfer functions of the circuit shown in figure 54 . 470pf out 100k in 1k 02735-049 figure 54. test circuit: first-order low-pass filter, 101 gain and 3 khz corner frequency figure 57. 3 db filter bandwidth in hz
ad8628/ad8629/AD8630 rev. e | page 17 of 24 time (500 s/div) voltage (v) v out 0v 0v v in 02735-053 ch1 = 50mv/div ch2 = 1v/div a v = ?50 input overvoltage protection although the ad8628/ad8629/AD8630 are rail-to-rail input amplifiers, care should be taken to ensure that the potential difference between the inputs does not exceed the supply volt- age. under normal negative feedback operating conditions, the amplifier corrects its output to ensure that the two inputs are at the same voltage. however, if either input exceeds either supply rail by more than 0.3 v, large currents begin to flow through the esd protection diodes in the amplifier. these diodes are connected between the inputs and each supply rail to protect the input transistors against an electrostatic dis- charge event, and they are normally reverse-biased. however, if the input voltage exceeds the supply voltage, these esd diodes can become forward-biased. without current limiting, excessive amounts of current could flow through these diodes, causing permanent damage to the device. if inputs are subject to over- voltage, appropriate series resistors should be inserted to limit the diode current to less than 5 ma maximum. figure 58. positive input overload recovery for the ad8628 time (500 s/div) voltage (v) v out 0v 0v v in 02735-054 ch1 = 50mv/div ch2 = 1v/div a v = ?50 output phase reversal output phase reversal occurs in some amplifiers when the input common-mode voltage range is exceeded. as common-mode voltage is moved outside of the common-mode range, the outputs of these amplifiers can suddenly jump in the opposite direction to the supply rail. this is the result of the differential input pair shutting down, causing a radical shifting of internal voltages that results in the erratic output behavior. the ad8628/ad8629/AD8630 amplifiers have been carefully designed to prevent any output phase reversal, provided that both inputs are maintained within the supply voltages. if one or both inputs could exceed either supply voltage, a resistor should be placed in series with the input to limit the current to less than 5 ma. this ensures that the output does not reverse its phase. figure 59. positive input overload recovery for ltc2050 time (500 s/div) voltage (v) v out 0v 0v v in 02735-055 ch1 = 50mv/div ch2 = 1v/div a v = ?50 overload recovery time many auto-zero amplifiers are plagued by a long overload recovery time, often in ms, due to the complicated settling behavior of the internal nulling loops after saturation of the outputs. the ad8628/ad8629/AD8630 have been designed so that internal settling occurs within two clock cycles after output saturation happens. this results in a much shorter recovery time, less than 10 s, when compared to other auto-zero amplifiers. the wide bandwidth of the ad8628/ad8629/ AD8630 enhances performance when the parts are used to drive loads that inject transients into the outputs. this is a common situation when an amplifier is used to drive the input of switched capacitor adcs. figure 60. positive input overload recovery for lmc2001
ad8628/ad8629/AD8630 rev. e | page 18 of 24 time (500 s/div) voltage (v) v out 0v 0v v in 02735-056 ch1 = 50mv/div ch2 = 1v/div a v = ?50 the results shown in figure 58 to figure 63 are summarized in table 5 . table 5. overload recovery time positive overload recovery (s) negative overload recovery (s) product ad8628 6 9 ltc2050 650 25,000 lmc2001 40,000 35,000 infrared sensors infrared (ir) sensors, particularly thermopiles, are increasingly being used in temperature measurement for applications as wide-ranging as automotive climate control, human ear thermometers, home insulation analysis, and automotive repair diagnostics. the relatively small output signal of the sensor demands high gain with very low offset voltage and drift to avoid dc errors. figure 61. negative input overload recovery for the ad8628 time (500 s/div) voltage (v) v out 0v 0v v in 02735-057 ch1 = 50mv/div ch2 = 1v/div a v = ?50 if interstage ac coupling is used, as in figure 64 , low offset and drift prevent the input amplifiers output from drifting close to saturation. the low input bias currents generate minimal errors from the sensors output impedance. as with pressure sensors, the very low amplifier drift with time and temperature elimi- nate additional errors once the temperature measurement is calibrated. the low 1/f noise improves snr for dc measure- ments taken over periods often exceeding one-fifth of a second. figure 64 shows a circuit that can amplify ac signals from 100 v to 300 v up to the 1 v to 3 v levels, with gain of 10,000 for accurate a/d conversion. figure 62. negative input overload recovery for ltc2050 5v 100k 10k 5v 100 v ? 300 v 100 to bias voltage 10k f c 1.6hz ir detector 100k 10 f 1/2 ad8629 1/2 ad8629 02735-059 time (500 s/div) voltage (v) v out 0v 0v v in 02735-058 ch1 = 50mv/div ch2 = 1v/div a v = ?50 figure 64. ad8629 used as preamplifier for thermopile figure 63. negative input overload recovery for lmc2001
ad8628/ad8629/AD8630 rev. e | page 19 of 24 precision current shunt sensor output amplifier for high precision dacs a precision current shunt sensor benefits from the unique attributes of auto-zero amplifiers when used in a differencing configuration, as shown in the ad8628/ad8629/ad8360 are used as output amplifiers for a 16-bit high precision dac in a unipolar configuration. in this case, the selected op amp needs to have very low offset voltage (the dac lsb is 38 v when operated with a 2.5 v reference) to eliminate the need for output offset trims. input bias current (typically a few tens of picoamperes) must also be very low, because it generates an additional zero code error when multiplied by the dac output impedance (approximately 6 k). figure 65 . current shunt sensors are used in precision current sources for feedback control systems. they are also used in a variety of other applications, including battery fuel gauging, laser diode power measurement and control, torque feedback controls in electric power steering, and precision power metering. r s 0.1 supply i r l 100 100k c 5v 100 100k c e = 1,000 r s i 100mv/ma ad8628 02735-060 rail-to-rail input and output provide full-scale output with very little error. output impedance of the dac is constant and code- independent, but the high input impedance of the ad8628/ ad8629/AD8630 minimizes gain errors. the amplifiers wide bandwidth also serves well in this case. the amplifiers, with settling time of 1 s, add another time constant to the system, increasing the settling time of the output. the settling time of the ad5541 is 1 s. the combined settling time is approxi- mately 1.4 s, as can be derived from the following equation: () ( ) () 2 2 8628 adtdact totalt s s s + = figure 65. low-side current sensing in such applications, it is desirable to use a shunt with very low resistance to minimize the series voltage drop; this minimizes wasted power and allows the measurement of high currents while saving power. a typical shunt might be 0.1 . at measured current values of 1 a, the shunts output signal is hundreds of mv, or even v, and amplifier error sources are not critical. however, at low measured current values in the 1 ma range, the 100 v output voltage of the shunt demands a very low offset voltage and drift to maintain absolute accuracy. low input bias currents are also needed, so that injected bias current does not become a significant percentage of the measured current. high open-loop gain, cmrr, and psrr help to maintain the overall circuit accuracy. as long as the rate of change of the current is not too fast, an auto-zero amplifier can be used with excellent results. 03023-061 ad5541/ad5542 ad8628 dgnd *ad5542 only v dd ref(ref*) refs* out sclk din cs agnd 5v 2.5v unipolar output ldac* 0.1 f 10 f 0.1 f serial interface figure 66. ad8628 used as an output amplifier
ad8628/ad8629/AD8630 rev. e | page 20 of 24 outline dimensions * compliant to jedec standards mo-193-ab with the exception of package height and thickness. pin 1 1.60 bsc 2.80 bsc 1.90 bsc 0.95 bsc 0.20 0.08 0.60 0.45 0.30 8 4 0 0.50 0.30 0.10 max seating plane * 1.00 max * 0.90 0.87 0.84 2.90 bsc 54 12 3 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 0.50 (0.0196) 0.25 (0.0099) 45 8 0 1.75 (0.0688) 1.35 (0.0532) seating plane 0.25 (0.0098) 0.10 (0.0040) 4 1 85 5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497) 1.27 (0.0500) bsc 6.20 (0.2440) 5.80 (0.2284) 0.51 (0.0201) 0.31 (0.0122) coplanarity 0.10 controlling dimensions are in millimeters; inch dimensions (in parentheses) are rounded-off millimeter equivalents for reference only and are not appropriate for use in design compliant to jedec standards ms-012aa figure 69. 8-lead standard small outline package [soic_n] narrow body (r-8) dimensions shown in millimeters and (inches) figure 67. 5-lead thin small outline transistor package [tsot] (uj-5) dimensions shown in millimeters 0.80 0.60 0.40 8 0 4 8 1 5 4.90 bsc pin 1 0.65 bsc 3.00 bsc seating plane 0.15 0.00 0.38 0.22 1.10 max 3.00 bsc coplanarity 0.10 0.23 0.08 compliant to jedec standards mo-187aa pin 1 1.60 bsc 2.80 bsc 1.90 bsc 0.95 bsc 1 3 4 5 2 0.22 0.08 10 5 0 0.50 0.30 0.15 max seating plane 1.45 max 1.30 1.15 0.90 2.90 bsc 0.60 0.45 0.30 compliant to jedec standards mo-178a a figure 70. 8-lead mini small outline package [msop] (rm-8) dimensions shown in millimeters figure 68. 5-lead small outline transistor package [sot-23] (rt-5) dimensions shown in millimeters
ad8628/ad8629/AD8630 rev. e | page 21 of 24 4.50 4.40 4.30 14 8 7 1 6.40 bsc pin 1 5.10 5.00 4.90 0.65 bsc seating plane 0.15 0.05 0.30 0.19 1.20 max 1.05 1.00 0.80 0.20 0.09 8 0 0.75 0.60 0.45 coplanarity 0.10 compliant to jedec standards mo-153ab-1 controlling dimensions are in millimeters; inch dimensions (in parentheses) are rounded-off millimeter equivalents for reference only and are not appropriate for use in design coplanarit y 0.10 14 8 7 1 6.20 (0.2441) 5.80 (0.2283) 4.00 (0.1575) 3.80 (0.1496) 8.75 (0.3445) 8.55 (0.3366) 1.27 (0.0500) bsc seating plane 0.25 (0.0098) 0.10 (0.0039) 0.51 (0.0201) 0.31 (0.0122) 1.75 (0.0689) 1.35 (0.0531) 8 0 0.50 (0.0197) 0.25 (0.0098) 1.27 (0.0500) 0.40 (0.0157) 0.25 (0.0098) 0.17 (0.0067) compliant to jedec standards ms-012ab 45 figure 71. 14-lead standard small outline package [soic_n] narrow body (r-14) dimensions shown in millimeters and (inches) figure 72. 14-lead thin shrink small outline package [tssop] (ru-14) dimensions shown in millimeters
ad8628/ad8629/AD8630 rev. e | page 22 of 24 ordering guide model temperature range package desc ription package option branding ad8628auj-r2 ?40c to +125c 5-lead tsot-23 uj-5 ayb ad8628auj-reel ?40c to +125c 5-lead tsot-23 uj-5 ayb ad8628auj-reel7 ?40c to +125 c 5-lead tsot-23 uj-5 ayb ad8628aujz-r2 1 ?40c to +125c 5-lead tsot-23 uj-5 a0l ad8628aujz-reel 1 ?40c to +125c 5-lead tsot-23 uj-5 a0l ad8628aujz-reel7 1 ?40c to +125c 5-lead tsot-23 uj-5 a0l ad8628ar ?40c to +125c 8-lead soic_n r-8 ad8628ar-reel ?40c to +125 c 8-lead soic_n r-8 ad8628ar-reel7 ?40c to +125 c 8-lead soic_n r-8 ad8628arz 1 ?40c to +125c 8-lead soic_n r-8 ad8628arz-reel 1 ?40c to +125c 8-lead soic_n r-8 ad8628arz-reel7 1 ?40c to +125c 8-lead soic_n r-8 ad8628art-r2 ?40c to +125c 5-lead sot-23 rt-5 aya ad8628art-reel7 ?40c to +125 c 5-lead sot-23 rt-5 aya ad8628artz-r2 1 ?40c to +125c 5-lead sot-23 rt-5 a0l ad8628artz-reel7 1 ?40c to +125c 5-lead sot-23 rt-5 a0l ad8629arz 1 ?40c to +125c 8-lead soic_n r-8 ad8629arz-reel 1 ?40c to +125c 8-lead soic_n r-8 ad8629arz-reel7 1 ?40c to +125c 8-lead soic_n r-8 ad8629armz-r2 1 ?40c to +125c 8-lead msop rm-8 a06 ad8629armz-reel 1 ?40c to +125c 8-lead msop rm-8 a06 AD8630aruz 1 ?40c to +125c 14-lead tssop ru-14 AD8630aruz-reel 1 ?40c to +125c 14-lead tssop ru-14 AD8630arz 1 ?40c to +125c 14-lead soic_n r-14 AD8630arz-reel 1 ?40c to +125c 14-lead soic_n r-14 AD8630arz-reel7 1 ?40c to +125c 14-lead soic_n r-14 1 z = pb-free part.
ad8628/ad8629/AD8630 rev. e | page 23 of 24 notes
ad8628/ad8629/AD8630 rev. e | page 24 of 24 notes ?2005 analog devices, inc. all ri ghts reserved. trademarks and registered trademarks are the prop erty of their respective owners. c02735C0C5/05(e)

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