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max4249?ax4257 ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps evaluation kit available for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com. general description the max4249?ax4257 low-noise, low-distortion oper- ational amplifiers offer rail-to-rail outputs and s ingle- supply operation down to 2.4v. they draw 400a of quiescent supply current per amplifier while featur ing ultra-low distortion (0.0002% thd), as well as low input voltage-noise density (7.9nv/ ! hz ) and low input current-noise density (0.5fa/ ! hz ). these features make the devices an ideal choice for portable/battery-po wered applications that require low distortion and/or low noise. for additional power conservation, the max4249/ max4251/max4253/max4256 offer a low-power shut- down mode that reduces supply current to 0.5? and puts the amplifiers outputs into a high-impedance state. the max4249-max4257s outputs swing rail-to- rail and their input common-mode voltage range includes ground. the max4250max4254 are unity- gain stable with a gain-bandwidth product of 3mhz. the max4249/max4255/max4256/max4257 are inter- nally compensated for gains of 10v/v or greater with a gain-bandwidth product of 22mhz. the single max4250 / max4255 are available in space-saving 5-pin sot23 packages. the max4252 is available in an 8-bump chi p- scale package (ucsp) and the max4253 is available in a 10-bump ucsp. the max4250aauk comes in a 5-pin sot23 package and is specified for operation over t he automotive (-40c to +125c) temperature range. applications wireless communications devicespa control portable/battery-powered equipment medical instrumentation adc buffers digital scales/strain gauges features ! available in space-saving ucsp, sot23, and ! max ? packages ! low distortion: 0.0002% thd (1k " load) ! 400 ! a quiescent supply current per amplifier ! single-supply operation from 2.4v to 5.5v ! input common-mode voltage range includesground ! outputs swing within 8mv of rails with a 10k " load ! 3mhz gbw product, unity-gain stable(max4250Cmax4254) 22mhz gbw product, stable with a v # 10v/v (max4249/max4255/max4256/max4257) ! excellent dc characteristics v os = 70 ! v i bias = 1pa large-signal voltage gain = 116db ! low-power shutdown mode reduces supply current to 0.5 ! a places outputs in a high-impedance state ! 400pf capacitive-load handling capability 19-1295; rev 9; 12/12 ordering information continued at end of data sheet . selector guide appears at end of data sheet. for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com. ucsp is a trademark and max is a registered tradem ark of maxim integrated products, inc. ab c 1 2 3 outa v dd outb ina- inb- inb+ v ss ina+ max4252 outa v dd outb ina- inb- ina+ inb+ v ss shdna shdnb max4253 c1 b1 a1 a2 a3 a4 b4 c2 c3 c4 top view(bumps on bottom) ucsp ucsp pin/bump configurations continued at end of data sh eet. pin/bump configurations ordering information part temp range pin-package top mark max4249 esd+ -40c to +85c 14 so max4249eub+ -40c to +85c 10 max max4250 euk+t -40c to +85c 5 sot23 acci m ax 4250aau k+ t - 40c to + 125c 5 sot23 aeyj + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps 2 maxim integrated max4249?ax4257 absolute maximum ratings electrical characteristics (v dd = 5v, v ss = 0v, v cm = 0v, v out = v dd /2, r l connected to v dd /2, shdn = v dd , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 2, 3) stresses beyond those listed under absolute maximu m ratings may cause permanent damage to the device . these are stress ratings only, and functional operation of the device at these or any other condi tions beyond those indicated in the operational sec tions of the specifications is not implied. exposur e to absolute maximum rating conditions for extended per iods may affect device reliability. power-supply voltage (v dd to v ss ) ......................+6.0v to -0.3v analog input voltage (in_+, in_-)....(v dd + 0.3v) to (v ss - 0.3v) shdn input voltage ......................................6.0v to (v ss - 0.3v) output short-circuit duration to either supply ..........continuous continuous power dissipation (t a = +70?) 5-pin sot23 (derate 7.1mw/? above +70?)...........571mw 8-bump ucsp (derate 4.7mw/? above +70?)........379mw 8-pin ?ax (derate 4.5mw/? above +70?) ............362mw 8-pin so (derate 5.88mw/? above +70?)...............471mw 10-bump ucsp (derate 6.1mw/? above +70?) ......484mw 10-pin ?ax (derate 5.6mw/? above +70?) ...........444mw 14-pin so (derate 8.33mw/? above +70?)..............667mw operating temperature range ...........................-40? to +85? max4250aauk .............................................-40? to +125? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) .......................................+260? parameter symbol conditions min typ max units supply voltage range v dd (note 4) 2.4 5.5 v v dd = 3v 400 e temperature 420 575 v dd = 5v max4250aauk 675 normal mode v dd = 5v, ucsp only 420 655 quiescent supply current per amplifier i q shutdown mode ( shdn = v ss ) (note 2) 0.5 1.5 ? e temperature 0.07 0.75 input offset voltage (note 5) v os max4250aauk 1.85 mv input offset voltage tempco tcv os 0.3 ?/? t a = +25? 0.1 1 t a = -40? to +85? 50 input bias current i b (note 6) t a = -40c to +125c 1500 pa t a = +25? 0.1 1 t a = -40? to +85? 10 input offset current i os (note 6) t a = -40c to +125c 100 pa differential input resistance r in 1000 g ! e temperature -0.2 v dd -1.1 input common-mode voltage range v cm guaranteed by cmrr test max4250aauk 0 v dd -1.1 v e temperature 70 115 common-mode rejection ratio cmrr v ss - 0.2v v cm v dd - 1.1v max4250aauk 68 db downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps maxim integrated 3 max4249?ax4257 electrical characteristics (continued)(v dd = 5v, v ss = 0v, v cm = 0v, v out = v dd /2, r l connected to v dd /2, shdn = v dd , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 2, 3) parameter symbol conditions min typ max units e temperature 75 100 power-supply rejection ratio psrr v dd 2.4v to 5.5v max4250aauk 72 db e temperature 80 116 r l = 10k ! to v dd /2; v out = 25mv to v dd 4.97v max4250aauk 77 e temperature 80 112 large-signal voltage gain a v r l = 1k ! to v dd /2; v out = 150v to v dd 4.75v max4250aauk 77 db e 8 25 v dd - v oh a 30 e 7 20 output voltage swing v out |v in+ - v in- | 10mv; r l = 10k ! to v dd /2 v ol - v ss a 25 mv e 77 200 v dd - v oh a 225 e 47 100 output voltage swing v out |v in+ - v in- | 10mv, r l = 1k ! to v dd /2 v ol - v ss a 125 mv output short-circuit current i sc 68 ma output leakage current i leak shutdown mode ( shdn = v ss ), v out = v ss to v dd (note 2) 0.001 1.0 ? shdn logic low v il (note 2) 0.2 x v d d v shdn logic high v ih (note 2) 0.8 x v dd v shdn input current i il /i ih shdn = v ss = v dd (note 2) 0.5 1.5 ? input capacitance 11 pf max4250max4254 3 gain-bandwidth product gbw max4249/max4255/max4256/max4257 22 mhz max4250max4254 0.3 slew rate sr max4249/max4255/max4256/max4257 2.1 v/s peak-to-peak input-noise voltage e n p-p f = 0.1hz to 10hz 760 nv p-p f = 10hz 27 f = 1khz 8.9 input voltage-noise density e n f = 30khz 7.9 nv/ hz input current-noise density i n f = 1khz 0.5 fa/ hz downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps 4 maxim integrated max4249?ax4257 electrical characteristics (continued)(v dd = 5v, v ss = 0v, v cm = 0v, v out = v dd /2, r l connected to v dd /2, shdn = v dd , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 2, 3) parameter symbol conditions min typ max units f = 1khz 0.0004 max4250max4254 a v = 1v/v, v out = 2v p-p , r l = 1k ! to gnd (note 7) f = 20khz 0.006 f = 1khz 0.0012 total harmonic distortion plus noise thd+n max4249/max4255/ max4256/max4257 a v = 1v/v, v out = 2v p-p , r l = 1k ! to gnd (note 7) f = 20khz 0.007 % capacitive-load stability no sustained oscillations 400 pf max4250max4254, a v = 1v/v 10 gain margin gm max4249/max4255/max4256/max4257, a v = 10v/v 12.5 db max4250max4254, a v = 1v/v 74 phase margin m max4249/max4255/max4256/max4257, a v = 10v/v 68 degrees max4250max4254 6.7 settling time to 0.01%, v out = 2v step max4249/max4255/ max4256/max4257 1.6 ? max4251/max4253 0.8 delay time to shutdown t sh i vdd = 5% of normal operation max4249/max4256 1.2 ? max4251/max4253 8 delay time to enable t en v out = 2.5v, v out settles to 0.1% max4249/max4256 3.5 ? power-up delay time t pu v dd = 0 to 5v step, v out stable to 0.1% 6 ? note 2: shdn is available on the max4249/max4251/max4253/max4256 only. note 3: all device specifications are 100% tested at t a = +25?. limits over temperature are guaranteed by design. note 4: guaranteed by the psrr test. note 5: offset voltage prior to reflow on the ucsp. note 6: guaranteed by design. note 7: lowpass-filter bandwidth is 22khz for f = 1khz and 80khz for f = 20khz. noise floor of test equipment = 10nv/ ! hz . downloaded from: http:///
0 10 5 2015 25 30 35 40 -95-55 -35 -75-13 7 2849 69 90 110131 152 172 192 max4251/max4256 input offset voltage distribution max4249-57 toc01 v os ( v) number of units 400 units v cm = 0 t a = +25 c -250 -100-150 -200 -50 0 50 100 150 200 250 -40 0 -20 20 40 60 80 offset voltage vs. temperature max4249-57 toc02 temperature ( c) v cm = 0 v os ( v) -50 0 100 50 150 200 -0.5 1.5 0.5 2.5 3.5 4.5 max4249-57 toc03 input common-mode voltage (v) input offset voltage ( v) v dd = 3v v dd = 5v input offset voltage vs. input common-mode voltage 0 0.30.2 0.1 0.4 0.5 0.6 0 43 1 2 5 6 7 8 9 10 output voltage vs. output load current max4249-57 toc04 output load current (ma) output voltage (v) v dd = 3v or 5v v diff = 10mv v dd - v oh v ol 0 0.030.02 0.01 0.04 0.05 0.06 0.07 0.08 0.09 0.10 -40 0 -20 20 60 40 80 output voltage swing (v oh ) vs. temperature max4249-57 toc05 temperature ( c) r l = 1k r l = 10k r l = 100k v dd - v oh (v) 0 0.020.01 0.03 0.04 0.05 0.06 -40 0 -20 20 60 40 80 output voltage swing (v ol ) vs. temperature max4249 -57toc06 temperature ( c) v ol (v) r l = 10k r l = 1k r l = 100k 50 7060 100 9080 130120 110 140 0 100 50 150 200 250 large-signal voltage gain vs. output voltage swing max4249-57 toc07 v out swing from either supply (mv) v dd = 3v r l referenced to gnd r l = 2k r l = 20k r l = 200k a v (db) 60 70 80 90 100 110 120 130 140 0 50 100 150 200 250 large-signal voltage gain vs. output voltage swing max4249-57 toc08 v out swing from either supply (mv) v dd = 3v r l referenced to gnd r l = 2k r l = 20k r l = 200k a v (db) 50 7060 100 9080 130120 110 140 0 100 50 150 200 250 max4249-57 toc09 large-signal voltage gain vs. output voltage swing v out swing from either supply (mv) v dd = 5v r l referenced to gnd r l = 2k r l = 20k r l = 200k a v (db) ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps maxim integrated 5 max4249?ax4257 typical operating characteristics (v dd = 5v, v ss = 0v, v cm = v out = v dd /2, input noise floor of test equipment =10nv/ ! hz for all distortion measurements, t a = +25?, unless otherwise noted.) downloaded from: http:///
50 8070 60 90 100 110 120 130 140 150 0 100 50 150 200 250 max4249-57 toc10 v dd = 5v r l referenced to gnd large-signal voltage gain vs. output voltage swing v out swing from either supply (mv) r l = 2k r l = 20k r l = 200k a v (db) 100 110105 115 120 125 -40 0 -20 20 60 40 80 large-signal voltage gain vs. temperature max4249-57 toc11 temperature ( c) r l referenced to v dd /2 v dd = 5v a v (db) r l = 1k v out = 150mv to 4.75mv r l = 100k v out = 10mv to 4.99mv r l = 10k v out = 20mv to 4.975mv 0.373 0.374 0.375 0.376 340 380360 400 420 440 460 -40 0 -20 20 60 40 80 supply current and shutdown supply current vs. temperature max4249-57 toc12 temperature ( c) shutdown supply current ( a) per amplifier shdn = v dd supply current ( a) shdn = v ss 320 340 360 380 400 420 440 0 0.1 0.2 0.3 0.4 0.5 0.6 1.8 2.8 2.3 3.3 3.8 4.3 4.8 5.3 5.5 supply current and shutdown supply current vs. supply voltage max4249-57 toc13 supply voltage (v) supply current ( a) shutdown supply current ( a) per amplifier shdn = v dd shdn = v ss 2000 100 0.001 0.1 1 0.01 5 supply current vs. output voltage max4249-57 toc14 output voltage (v) supply current ( a) 1000 400 v dd = 5v v dd = 3v 40 60 80 120100 180160 140 1.8 2.3 2.8 3.3 3.8 4.3 4.8 5.3 input offset voltage vs. supply voltage max4249-57 toc15 supply voltage (v) v os ( v) v cm = 0 v out = v dd /2 r l referenced to gnd r l = 10k r l = 1k r l = 100k 60 -40 100 10k 100k 1m 1k 10m max4250?ax4254 gain and phase vs. frequency -20 -10 0 -30 max4249-57 toc16 frequency (hz) gain (db) phase (degrees) 10 20 30 40 50 180 -180 -108 -72 -36 -144 0 36 72 108 144 gain phase v dd = 3v, 5v r l = 50k c l = 20pf a v = 1000 60 -40 100 10k 100k 1m 1k 10m max4249/max4255/max4256/max4257 gain and phase vs. frequency -20 -10 0 -30 max4249-57 toc17 frequency (hz) gain (db) phase (degrees) 10 20 30 40 50 180 -180 -108 -72 -36 -144 0 36 72 108 144 gain phase v dd = 3v, 5v r l = 50k c l = 20pf a v = 1000 0 -100-110 1 1k 10k 100k 1m 10 100 10m max4250?ax4254 power-supply rejection ratio vs. frequency -80 -70 -60-90 max4249-57 toc18 frequency (hz) psrr (db) -50 -40 -30 -20 -10 psrr+ psrr- v dd = 3v, 5v ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps 6 maxim integrated max4249?ax4257 typical operating characteristics (continued) (v dd = 5v, v ss = 0v, v cm = v out = v dd /2, input noise floor of test equipment =10nv/ ! hz for all distortion measurements, t a = +25?, unless otherwise noted.) downloaded from: http:///
1000 0.1 1k 10k 100k 1m 10m output impedance vs. frequency max4249-57 toc19 frequency (hz) output impedance ( ) 1 10 100 a v = 1 (max4250?ax4254) a v = 10 (max4249/max4255/ max4256/max4257) 30 0 10 100 1k 10k 100k input voltage-n0ise density vs. frequency max4249-57 toc20 frequency (hz) vn-equivalent input noise-voltage (nv/ hz) 5 10 15 20 25 200nv/div 1s/div 0.1hz to 10hz p-p noise max4249-57 toc21 v dd = 3v or 5v v p-p noise = 760nv p-p -160 -140 -120 -100 -80 -60 -40 -20 0 max4250?ax4254 fft of distortion and noise frequency (hz) amplitude (dbc) 10 5k 10k 15k 20k max4249-57 toc22 r l = 1k f o = 1khz a v = 1 f o hd2 hd3 hd4 hd5 v out = 2v p-p -140 -120 -100 -80 -60 -40 -20 0 20 10 5k 10k 15k 20k max4249/max4255/max4256/max4257 fft of distortion and noise max4249-57 toc23 frequency (hz) amplitude (dbc) v out = 4v p-p f o = 1khz hd2 hd3 v in 10k 100k 11k f o v o 0.001 0.01 0.1 1 10 0 2 1 3 4 5 max4250?ax4254 total harmonic distortion plus noise vs. output voltage (v dd = 5v) max4249-57 toc24 output voltage (v p-p ) thd+n (%) v in r l = 1k 100k 11k a v = 10 f o = 3khz filter bw = 30khz v o r l r l = 10k r l = 100k 0.001 0.01 0.1 1 10 0 2 1 3 max4249-57 toc25 output voltage (v p-p ) thd+n (%) 100k 11k max4250?ax4254 total harmonic distortion plus noise vs. output voltage swing (v dd = 3v) v out v in r l r l = 1k r l = 10k r l = 100k a v = 10 f o = 3khz filter bw = 30khz 0.001 0.01 0.1 1 0 3 4 1 2 5 max4249-57 toc26 output voltage (v p-p ) thd+n (%) f o = 20khz, filter bw = 80khz 100k 11k max4249/max4255/max4256/max4257 total harmonic distortion plus noise vs. output voltage swing v out v in r l a v = 10 f o = 3khz, filter bw = 30khz 0.0001 0.01 0.001 0.1 1 10 1k 100 10k max4250?ax4254 total harmonic distortion plus noise vs. frequency max4249-57 toc27 frequency (hz) thd+n (%) r2 r1 r1 = 560 , r2 = 53k v in v out r l a v = 100 a v = 10 r1 = 5.6k , r2 = 53k filter bw = 22khz r l = 10k to gnd v o = 2v p-p a v = 1 ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps maxim integrated 7 max4249?ax4257 typical operating characteristics (continued) (v dd = 5v, v ss = 0v, v cm = v out = v dd /2, input noise floor of test equipment =10nv/ ! hz for all distortion measurements, t a = +25?, unless otherwise noted.) downloaded from: http:///
0.0001 0.001 0.01 0.1 10 1k 100 10k max4250?ax4254 total harmonic distortion plus noise vs. frequency max4249-57 toc28 frequency (hz) thd+n(%) filter bw = 80khz a v = 1 r l = 1k v out = 2v p-p r l to v dd /2 r l to gnd r l to v dd v out 200mv/div 1.5v0.5v 2 s/div max4250?ax4254 large-signal pulse response max4249-57 toc29 v dd = 3v r l = 10k c l = 100pf v in = 1v pulse 0.6v0.5v max4249-57 toc30 max4250?ax4254 small-signal pulse response v out 20mv/div v dd = 3v r l = 10k c l = 100pf v in = 100v pulse 2 s/div 2v1v max4249/max4255/max4256/max4257 large-signal pulse response max4249-57 toc31 v out 200mv/div v dd = 3v r l = 10k c l = 100pf v in = 100mv pulse a v = 10 2 s/div 1.6v1.5v max4249/max4255/max4256/max4257 small-signal pulse response max4249-57 toc32 v out 50mv/div v dd = 3v r l = 10k c l = 100pf v in = 10mv pulse a v = 10 2 s/div 140 130 0 channel separation vs. frequency max4249-57 toc33 frequency (hz) channel separation (db) 100 110 120 9080 70 1k 100k 1m 10k 10m ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps 8 maxim integrated max4249?ax4257 typical operating characteristics (continued) (v dd = 5v, v ss = 0v, v cm = v out = v dd /2, input noise floor of test equipment =10nv/ ! hz for all distortion measurements, t a = +25?, unless otherwise noted.) downloaded from: http:///
detailed description the max4249max4257 single-supply operational amplifiers feature ultra-low noise and distortion w hile consuming very little power. their low distortion and low noise make them ideal for use as preamplifiers in wide dynamic-range applications, such as 16-bit analog-t o- digital converters (see typical operating circuit ). their high-input impedance and low noise are also useful for signal conditioning of high-impedance sources, such as piezoelectric transducers. these devices have true rail-to-rail output operati on, drive loads as low as 1k " while maintaining dc accura- cy, and can drive capacitive loads up to 400pf without oscillation. the input common-mode voltage range extends from v dd - 1.1v to 200mv beyond the negative rail. the push-pull output stage maintains excellent dc characteristics, while delivering up to ?ma of current. the max4250?254 are unity-gain stable, whereas, the max4249/max4255/max4256/max4257 have a higher slew rate and are stable for gains # 10v/v. the max4249/max4251/max4253/max4256 feature a low- power shutdown mode, which reduces the supply cur- rent to 0.5? and disables the outputs. the max4250aauk is specified for operation over the automotive (-40? to +125?) temperature range. pin/bump description pin/bump m a x4 2 5 0 / m a x4 2 5 5 m a x4 2 5 1 / m a x4 2 5 6 m a x4 2 5 2 / m a x4 2 5 7 m a x4 2 5 2 m a x4 2 4 9 / m a x4 2 5 3 m a x4 2 5 4 5-pin sot23 8-pin so/max 8-pin so/max 8-bump ucsp 10-bump ucsp 10-pin max 1 4 - pin so 14-pin so name function 1 6 1, 7 a1, a3 a1, c1 1, 9 1, 13 1, 7, 8, 14 out, outa, outb, outc, outd amplifier output 2 4 4 c2 b4 4 4 11 v ss negative supply. connect to ground for single- supply operation 3 3 3, 5 c1, c3 a3, c3 3, 7 3, 11 3, 5, 10, 12 in + , in a+ , in b+ , in c + , in d + noninverting amplifier input 4 2 2, 6 b1, b3 a2, c2 2, 8 2, 12 2, 6, 9, 13 in-, ina-, inb-, inc-, ind- inverting amplifier input 5 7 8 a2 b1 10 14 4 v dd positive supply 8 a4, c4 5, 6 6, 9 shdn , shdna , shdnb shutdown input, connect to v dd or leave unconnected for normal operation (amplifier(s) enabled). 1, 5 5, 7, 8, 10 n.c. no connection. not internally connected. b2 b2, b3 not populated with solder sphere ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps maxim integrated 9 max4249?ax4257 downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps 10 maxim integrated max4249?ax4257 low distortion many factors can affect the noise and distortion that the device contributes to the input signal. the followi ng guidelines offer valuable information on the impact of design choices on total harmonic distortion (thd). choosing proper feedback and gain resistor values for a particular application can be a very important factor in reducing thd. in general, the smaller the closed - loop gain, the smaller the thd generated, especiall y when driving heavy resistive loads. large-value fee d- back resistors can significantly improve distortion. the thd of the part normally increases at approximately 20db per decade, as a function of frequency. operating the device near or above the full-power bandwidth significantly degrades distortion. referencing the load to either supply also improves the part? distortion performance, because only one of the mosfets of the push-pull output stage drives the out- put. referencing the load to midsupply increases th e part? distortion for a given load and feedback setting. (see the total harmonic distortion vs. frequency graph in the typical operating characteristics .) for gains # 10v/v, the decompensated devices max4249/max4255/max4256/max4257 deliver the best distortion performance, since they have a high er slew rate and provide a higher amount of loop gain for a given closed-loop gain setting. capacitive loads below 400pf, do not significantly affect distortion results. distortion performance remains relatively con- stant over supply voltages. low noise the amplifiers input-referred, noise-voltage densi ty is dominated by flicker noise at lower frequencies, and by thermal noise at higher frequencies. because the ther- mal noise contribution is affected by the parallel combi- nation of the feedback resistive network (r f || r g , figure 1), these resistors should be reduced in cases where the system bandwidth is large and thermal noise is dominant. this noise contribution factor decreas es, however, with increasing gain settings. for example, the input noise-voltage density of the cir- cuit with r f = 100k " , r g = 11k " (a v = 10v/v) is e n = 15nv/ ! hz , e n can be reduced to 9nv/ ! hz by choosing r f = 10k " , r g = 1.1k " (a v = 10v/v), at the expense of greater current consumption and potentially high er distortion. for a gain of 100v/v with r f = 100k " , r g = 1.1k " , the e n is low (9nv/ ! hz ). c z r f v out v in r g 0 100mv a v = 2v/v r f = r g = 10k v in = 50mv/div v out = 100mv/div 2 s/div 0 100mv a v = 2 r f = r g = 100k c z = 11pf 50mv/div 100mv/div v in v out 2 s/div figure 1. adding feed-forward compensation figure 2a. pulse response with no feed-forward compensation figure 2b. pulse response with 10pf feed-forward compensation downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps maxim integrated 11 max4249?ax4257 using a feed-forward compensation capacitor, c z the amplifier? input capacitance is 11pf. if the resis- tance seen by the inverting input is large (feedbac k network), this can introduce a pole within the amplifier? bandwidth, resulting in reduced phase margin. compensate the reduced phase margin by introducing a feed-forward capacitor (c z ) between the inverting input and the output (figure 1). this effectively cancels the pole from the inverting input of the amplifier. choose the value of c z as follows: c z = 11 x (r f / r g ) [pf] in the unity-gain stable max4250max4254, the use o f a proper c z is most important for a v = 2v/v, and a v = -1v/v. in the decompensated max4249/ max4255/max4256/max4257, c z is most important for a v = 10v/v. figures 2a and 2b show transient response both with and without c z . using a slightly smaller c z than suggested by the for- mula above achieves a higher bandwidth at the expense of reduced phase and gain margin. as a gen- eral guideline, consider using c z for cases where r g || r f is greater than 20k " (max4250max4254) or greater than 5k " (max4249/max4255/max4256/ max4257). applications information the max4249max4257 combine good driving capa- bility with ground-sensing input and rail-to-rail o utput operation. with their low distortion, low noise, and low- power consumption, these devices are ideal for use in portable instrumentation systems and other low-power, noise-sensitive applications. ground-sensing and rail-to-rail outputs the common-mode input range of these devices extends below ground, and offers excellent common- mode rejection. these devices are guaranteed not to undergo phase reversal when the input is overdriven (figure 3). figure 4 showcases the true rail-to-rail output ope ra- tion of the amplifier, configured with a v = 10v/v. the output swings to within 8mv of the supplies with a 10k " load, making the devices ideal in low-supply- voltage applications. output loading and stability even with their low quiescent current of 400a, the se amplifiers can drive 1k " loads while maintaining excel- lent dc accuracy. stability while driving heavy capaci- tive loads is another key feature. v out v in r iso c l max4250 max4251 max4252 max4253 max4254 4.25v 4.45v -200mv 00 v out v in a v = 1 v dd = 5v r l = 10k 20 s/div 0 5v v dd = 5v r l = 10k a v = 10 f = 1khz 200 s/div v out 1v/div figure 3. overdriven input showing no phase reversal figure 4. rail-to-rail output operation figure 5. capacitive-load driving circuit downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps 12 maxim integrated max4249?ax4257 these devices maintain stability while driving loads up to 400pf. to drive higher capacitive loads, place a small isolation resistor in series between the output of the amplifier and the capacitive load (figure 5). t his resistor improves the amplifiers phase margin by i so- lating the capacitor from the op amps output. reference figure 6 to select a resistance value that will ensure a load capacitance that limits peaking to <2db (25%). for example, if the capacitive load is 1000p f, the corresponding isolation resistor is 150 " . figure 7 shows that peaking occurs without the isolation res is- tor. figure 8 shows the unity-gain bandwidth vs. capac- itive load for the max4250?ax4254. power supplies and layout the max4249?ax4257 operate from a single 2.4v to 5.5v power supply or from dual supplies of ?.20v to ?.75v. for single-supply operation, bypass the power supply with a 0.1? ceramic capacitor placed close to the v dd pin. if operating from dual supplies, bypass each supply to ground. good layout improves performance by decreasing the amount of stray capacitance and noise at the op amp? inputs and output. to decrease stray capacitance, min- imize pc board trace lengths and resistor leads, an d place external components close to the op amp? pins. 160140 0 10 10,000 6020 40 120100 80 capacitive loading (pf) 1000 100 shaded area indicatesstable operation with no need for isolation resistor. note: using an isolation resistor reduces peaking. r iso ( ) 4.53.5 4.0 0 10 10,000 2.0 3.02.5 1.0 0.5 1.5 capacitive load (pf) unity-gain bandwidth (mhz) 1000 100 v dd = 3v shaded area indicatesstable operation with no need for isolation resistor. note: r iso chosen for peaking < 2db. 2520 0 10 10,000 15 5 10 capacitive load (pf) peaking (db) 1000 100 max4250?ax4254 (a v = 1) max4249/max4255?ax4257 (a v = 10) r iso = 0 shaded area indicatesstable operation with no need for isolation resistor. figure 6. isolation resistance vs. capacitive loading to minimize peaking (<2db) figure 7. peaking vs. capacitive load figure 8. max4250?ax4254 unity-gain bandwidth vs. capacitive load downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps maxim integrated 13 max4249?ax4257 typical operating circuit max195 (16-bit adc) serialinterface dout sclk shdn shdn ain v in ref -5v 2 50k 5v 3 4 6 78 5k v dd v ss 4.096v cs max4256 selector guide part g a in b a n d wid t h ( m h z) minimum stable gain (v/v) no. of amplifiers per package shutdown mode pin-package max4249 22 10 2 yes 10-pin max, 14-pin so max4250/a 3 1 1 5-pin sot23 max4251 3 1 1 yes 8-pin max/so max4252 3 1 2 8- p i n m ax /s o , 8- b um p u c s p max4253 3 1 2 yes 10-pin max, 14-pin so, 10-bump ucsp max4254 3 1 4 14-pin so max4255 22 10 1 5-pin sot23 max4256 22 10 1 yes 8-pin max/so max4257 22 10 2 8-pin max/so downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps 14 maxim integrated max4249?ax4257 v ss in- in+ 1 5 v dd out max4250 max4250a max4255 sot23 top view 2 3 4 out n.c. v ss 12 8 7 shdn v dd in- in+ n.c. max/so 3 4 6 5 max4251 max4256 inb- inb+ v ss 12 8 7 v dd outb ina- ina+ outa max/so 3 4 6 5 max4252 max4257 1 23 4 5 10 98 7 6 v dd outbinb- inb+ v ss ina+ ina- outa max4249 max4253 max shdnb shdna 1413 12 11 10 9 8 1 23 45 6 7 v dd outbinb- inb+ v ss ina+ ina- outa max4249 max4253 n.c. shdnb n.c. n.c. shdna n.c. so 1413 12 11 10 9 8 1 23 45 6 7 outdind- ind+ v ss v dd ina+ ina- outa max4254 inc+ inc- outc outb inb- inb+ so + + + + + + pin/bump configurations (continued) part temp range pin-package top m ark max4251 esa+ -40c to +85c 8 so max4251eua+ -40c to +85c 8 max max4252 ebl+t -40c to +85c 8 ucsp aao max4252esa+ -40c to +85c 8 so max4252eua+ -40c to +85c 8 max max4253 ebc+t -40c to +85c 10 ucsp aak max4253eub+ -40c to +85c 10 max max4253esd+ -40c to +85c 14 so max4254 esd+ -40c to +85c 14 so max4255 euk+t -40c to +85c 5 sot23 ac c j max4256 esa+ -40c to +85c 8 so max4256eua+ -40c to +85c 8 max max4257 esa+ -40c to +85c 8 so max4257esa/v+ t -40c to +85c 8 so max4257eua+ -40c to +85c 8 max ordering information (continued) downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps maxim integrated 15 max4249?ax4257 package type package code outline no. land pattern no. 5 sot-23 u5+2 21-0057 90-0174 8 max u8+1 21-0036 90-0092 10 max u10+2 21-0061 90-0330 3 x 3 csp b9+5 21-0093 14 soic s14+1 21-0041 90-0112 12 csp b12+4 21-0104 package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages . note that a "+", "#", or "-" in the package code indicates rohs status only. package drawings may show a different suffix character, but th e drawing pertains to the package regardless of rohs status. downloaded from: http:///
ucsp, single-supply, low-noise, low-distortion, rail-to-rail op amps max4249?ax4257 maxim integrated cannot assume responsibility for u se of any circuitry other than circuitry entirely e mbodied in a maxim integrated product. no circuit p atent licenses are implied. maxim integrated reserves the right to change the circuitry and specifications w ithout notice at any time. the parametric values (m in and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quot ed in this data sheet are provided for guidance. 16 maxim integrated 160 rio robles, san jose, ca 95134 usa 1-408-601-1000 2012 maxim integrated products, inc. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. revision history revision number revision date description pages changed 8 10/11 added lead-free packaging to the ordering information and changed the input bias current and input offset current conditions in the electrical characteristics table 1, 2, 14 9 12/12 added max4257esa/v+t to ordering information . 14 downloaded from: http:///

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