View AD8225-EVAL_1083409.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

rev. a 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. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective companies. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781/329-4700 www.analog.com fax: 781/326-8703 ? 2003 analog devices, inc. all rights reserved. ad8225 precision gain of 5 instrumentation amplifier features no external components required highly stable, factory trimmed gain of 5 low power, 1.2 ma max supply current wide power supply range ( 1.7 v to 18 v) single- and dual-supply operation excellent dynamic performance high cmrr 86 db min @ dc 80 db min to 10 khz wide bandwidth 900 khz 4 v to 36 v single supply high slew rate 5 v/ s min outstanding dc precision low gain drift 5 ppm/ c max low input offset voltage 150 v max low offset drift 2 v/ c max low input bias current 1.2 na max applications patient monitors current transmitters multiplexed systems 4 to 20 ma converters bridge transducers sensor signal conditioning functional block diagram 8 7 6 5 1 2 3 4 nc = no connect nc ?n +in ? s nc +v s v out ref ad8225 general description the ad8225 is an instrumentation amplifier with a fixed gain of 5, which sets new standards of performance. the superior cmrr of the ad8225 enables rejection of high frequency common-mode voltage (80 db min @ 10 khz). as a result, higher ambient levels of noise from utility lines, industrial equipment, and other radiating sources are rejected. extended cmv range enables the ad8225 to extract low level differential signals in the presence of high common-mode dc voltage levels even at low supply voltages. ambient electrical noise from utility lines is present at 60 hz and harmonic frequencies. power systems operating at 400 hz create high noise environments in aircraft instrument clusters. good cmrr performance over frequency is necessary if power system generated noise is to be rejected. the dc to 10 khz frequency ?hz 140 1 100k 10 cmrr ?db 100 1k 10k 130 120 110 100 90 80 70 60 50 40 30 high performance in amp @ gain of 5 ad8225 figure 1. typical cmrr vs. frequency cmrr performance of the ad8225 rejects noise from utility systems, motors, and repair equipment on factory floors, switch- ing power supplies, and medical equipment. low input bias currents combined with a high slew rate of 5 v/ s make the ad8225 ideally suited for multiplexed applications. the ad8225 provides excellent dc precision, with maximum input offset voltage of 150 v and drift of 2 v/ c. gain drift is 5ppm/ c or less. operating on either single or dual supplies, the fixed gain of 5 and wide input common-mode voltage range make the ad8225 well suited for patient monitoring applications. the ad8225 is packaged in an 8-lead soic package and is specified over the standard industrial temperature range, C 40 c to +85 c.
rev. a e2e ad8225especifications (t a = 25 c, v s = 15 v, r l = 2 k , unless otherwise noted.) parameter conditions min typ max unit gain gain 5v/v gain error ? 0.1 +0.05 +0.1 % nonlinearity 2 10 ppm vs. temperature 1 5 ppm/ c offset voltage (rti) offset voltage 50 150 v vs. temperature 0.3 2 v/ c vs. supply (psrr) 90 100 db input input operating impedance differential 10 2g pf common mode 10 2g pf input voltage range ? v s + 1.6 +v s ? 1.0 v (common-mode) vs. temperature ? v s + 2.2 +v s ? 1.2 v input bias current 0.5 1.2 na vs. temperature 3 pa/ c input offset current 0.15 0.5 na vs. temperature 1.5 pa/ c common-mode rejection ratio 86 94 db t a = t min to t max 83 db f = 10 khz * 80 db output operating voltage range r l = 2 k ? v s + 1.4 +v s ? 1.4 v vs. temperature ? v s + 1.5 +v s ? 1.6 v operating voltage range r l = 10 k ? v s + 1.0 +v s ? 1.1 v vs. temperature ? v s + 1.2 +v s ? 1.0 v short circuit current 18 ma dynamic response small signal ? 3 db bandwidth 900 khz full power bandwidth v out = 20 v p-p 75 khz settling time (0.01%) 10 v step 3.4 s settling time (0.001%) 10 v step 4.8 s slew rate 5 v/ s noise (rti) voltage 0.1 hz to 10 hz 1.5 v p-p spectral density, 1 khz 45 nv/ hz hzhz hz hz
rev. a ad8225 e3e parameter conditions min typ max unit gain gain 5v/v gain error ? 0.1 +0.05 +0.1 % nonlinearity 2 10 ppm vs. temperature 1 5 ppm/ c voltage offset (rti) offset voltage 125 325 v vs. temperature 2 v/ c vs. supply 90 100 db input input operating impedance differential 10 2g pf common-mode 10 2g pf input operating voltage range ? v s + 1.6 +v s ? 1.0 v vs. temperature ? v s + 2.1 +v s ? 1.5 v input bias current 0.5 1.2 na vs. temperature 3 pa/ c input offset current 0.15 0.5 na vs. temperature 1.5 pa/ c common-mode rejection ratio 86 94 db t a = t min to t max 83 db f = 10 khz * 80 db output operating voltage range r l = 2 k ? v s + 0.9 +v s ? 1.0 v vs. temperature ? v s + 1.0 +v s ? 1.2 v operating voltage range r l = 10 k ? v s + 0.8 +v s ? 1.0 v vs. temperature ? v s + 0.9 +v s ? 1.0 v short circuit current 18 ma dynamic response small signal ? 3 db bandwidth 900 khz full power bandwidth v out = 7.8 v p-p 170 khz settling time (0.01%) 7 v step 3 s settling time (0.001%) 7 v step 4.3 s slew rate 5 v/ s noise (rti) voltage 0.1 hz to 10 hz 1.5 v p-p spectral density, 1 khz 45 nv/ hz hzhz hz hz
rev. a e4e ad8225 parameter conditions min typ max unit gain gain 5v/v gain error ? 0.1 +0.05 +0.1 % nonlinearity 2 10 ppm vs. temperature 1 5 ppm/ c offset voltage (rti) offset voltage 150 375 v vs. temperature 2 v/ c vs. supply 90 100 db input input operating impedance differential 10 2g pf common mode 10 2g pf input voltage range 1.6 v s ? 1.05 v (common-mode) vs. temperature 1.7 v s ? 1.0 v input bias current 0.5 1.2 na vs. temperature 3 pa/ c input offset current 0.15 0.5 na vs. temperature 1.5 pa/ c common-mode rejection ratio 86 94 db t a = t min to t max 83 db f = 10 khz * 80 db output operating voltage range r l = 2 k 0.8 v s ? 1.05 v vs. temperature 0.9 v s ? 1.2 v operating voltage range r l = 10 k 0.8 v s ? 1.0 v vs. temperature 0.9 v s ? 1.0 v short circuit current 18 ma dynamic response small signal ? 3 db bandwidth 900 khz full power bandwidth v out = 3.2 v p-p 420 khz settling time (0.01%) 2 v step 3.3 s settling time (0.001%) 2 v step 5.1 s slew rate 5 v/ s noise (rti) voltage 0.1 hz to 10 hz 1.5 v p-p spectral density, 1 khz 45 nv/ hz hzhz hz hz
rev. a ad8225 ? pin function descriptions pin number mnemonic function 1n cm ay be connected to pin 4 to balance c in 2 ? in inverting input 3 +in noninverting input 4 ? v s negative supply voltage 5 ref connect to desired output cmv 6v out output 7+v s positive supply voltage 8nc absolute maximum ratings * supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 v internal power dissipation . . . . . . . . . . . . . . . . . . . . 650 mw input voltage (common-mode) . . . . . . . . . . . . . . . . . . . . v s differential input voltage . . . . . . . . . . . . . . . . . . . . . . . 25 v output short circuit duration . . . . . . . . . . . . . . . . indefinite storage temperature . . . . . . . . . . . . . . . . . . ? 65 c to +125 c operating temperature range . . . . . . . . . . . ? 40 c to +85 c lead temperature range (10 sec soldering) . . . . . . . . . 300 c * stresses above those listed under absolute maximum ratings may cause perma- nent damage to the device. this is a stress rating only and 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. ambient temperature ? c 1.5 1.0 0 ?0 80 ?0 power dissipation ?w ?0 ?0 ?0 0 10 2 03040506070 0.5 90 t j = 150 c 8-lead soic package figure 2. maximum power dissipation vs. temperature ordering guide model temperature range package description package options ad8225ar ? 40 c to +85 c 8-lead soic rn-8 ad8225ar-reel ? 40 c to +85 c 8-lead soic 13" reel ad8225ar-reel7 ? 40 c to +85 c 8-lead soic 7" reel AD8225-EVAL evaluation board rn-8 caution esd (electrostatic discharge) sensitive device. electrostatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge without detection. although the ad8225 features proprietary esd protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd precautions are recommended to avoid performance degradation or loss of functionality.
rev. a e6e ad8225etypical performance characteristics input offset voltage e v 50 20 0 e140 120 e120 % of units e80 e40 e20 0 20 40 60 80 45 25 15 5 35 30 10 40 lot size = 3775 e100 e60 100 tpc 1. typical distribution of input offset voltage, v s = 15 v input bias current e pa 50 20 0 e200 800 e100 % of units 0 100 200 300 400 500 700 45 25 15 5 35 30 10 40 lot size = 7550 600 tpc 2. typical distribution of input bias current, v s = 15 v input offset current e pa 50 20 0 e500 400 e400 % of units e300 e100 0 100 200 300 45 25 15 5 35 30 10 40 lot size = 3775 e200 tpc 3. typical distribution of input offset current, v s = 15 v temperature e c 250 e50 e60 100 e40 bias current e pa e20 0 20 40 60 80 200 150 100 50 0 +bias current ebias current tpc 4. bias current vs. temperature w arm-up time e min 8 6 0 05 1 change in offset voltage e v 234 4 2 tpc 5. offset voltage vs. warm-up time frequency e hz 1000 100 0 1 100k 10 vo ltag e noise density e nv/ hz
rev. a ad8225 ? frequency ?hz 1000 100 0 1 10k 10 vo ltag e noise density ?nv/ hz 100 1k tpc 7. input current noise spectral density vs. frequency 100 90 10 0 1s 10 time ?sec 5 noise ?rti ? v 0 4 ? ? ? ? 2 0 1 3 tpc 8. 0.1 hz to 10 hz voltage noise, rti 100 90 10 0 10 time ?sec 5 current noise ?2pa/div 0 ? ? ? 0 2 8 4 6 ? 1s tpc 9. 0.1 hz to 10 hz current noise frequency ?hz 130 110 30 1 100k 10 cmr ?db 100 1k 10k 90 70 50 120 100 80 60 40 tpc 10. cmr vs. frequency, rti temperature ? c 0.10 ?.10 ?0 100 ?0 cmrr drift ?ppm/ c 020406080 0.08 ?.02 ?.04 ?.06 ?.08 0.04 0 0.06 0.02 tpc 11. cmrr vs. temperature output voltage ?v 15 ?5 ?5 15 ?0 common-mode voltage ?v ? 0 5 10 10 5 0 ? ?0 v s = 15v v s = 5v tpc 12. cmv range vs. v out , dual supplies
rev. a e8e ad8225 output voltage e v 5 4 0 05 1 common-mode voltage e v 234 3 2 1 v s = 5v tpc 13. cmv vs. v out , single supply frequency e hz 140 120 0 0.1 1m 1 psrr e db 10 100 1k 100 80 60 40 20 10k 100k +v s ev s tpc 14. psrr vs. frequency, rti frequency e hz 100 10m 1k gain e db 10k 100k 1m 40 30 e60 20 10 0 e10 e20 e30 e40 e50 tpc 15. small signal frequency response, v out = 200 mv p-p frequency e hz 100 10m 1k gain e db 10k 100k 1m 40 30 e60 20 10 0 e10 e20 e30 e40 e50 tpc 16. large signal frequency response, v out = 4 v p-p +v s e0.0 e2.0 020 10 input voltage 5 e v (referred to supply voltages) e0.5 e1.0 e1.5 515 2.0 0 supply voltage e v 1.5 1.0 0.5 20 10 515 ev s +0.0 tpc 17. input common mode voltage range vs. supply voltage +v s 0 e2.0 020 16 output voltage swing e v (referenced to supply voltages) e0.5 e1.0 e1.5 4 ev s 0 2.0 0 supply voltage e v 1.5 1.0 0.5 14 218 610 812 20 16 414 218 610 812 r l = 10k r l = 2k r l = 10k r l = 2k tpc 18. output voltage swing vs. supply voltage and load resistance
rev. a ad8225 e9e load resistance e 30 25 0 10 100k 100 output voltage swing e v p-p 1k 15 10 5 20 tpc 19. output voltage swing vs. load resistance 100 90 0 output (5v/div) ch 2 = 10mv/div test circuit output (0.001%/div) horiz (4 s/div) ch 1 = 5v/div 10 tpc 20. large signal pulse response and settling time to 0.001% 100 90 10 0 output 2 1 input ch 1 = 10mv, ch 2 = 20mv, h = 2 s tpc 21. small signal pulse response, c l = 100 pf step size e v 10 9 0 020 51015 6 3 2 1 8 7 4 5 settling time e s 0.001% 0.01% tpc 22. settling time vs. step size 100 90 10 0 100mv 2v 10 output voltage e v 0 nonlinearity e ppm e10 4 e4 e3 e2 e1 2 0 1 3 tpc 23. gain nonlinearity supply voltage e v 1.5 0.9 0.5 0 20 2 supply current e ma 46810 12 14 16 18 1.4 1.0 0.8 0.6 1.2 1.1 0.7 1.3 +85 c +25 c e40 c tpc 24. i supply vs. v supply and temperature
rev. a ?0 ad8225 ad8225 ad797 g = 5 g = 100 lpf scope g = 100 test circuit 1. 1 hz to 10 hz voltage noise test ad8225 ad829 2k 20 100 20k 4k g = 5 g = 101 2k test circuit 2. settling time to 0.01% t est circuits
rev. a ad8225 e11e v b +v s a1 a2 c2 r2 ein q2 c1 r1 +in q1 3k 3k 15k 15k v ref a3 +v s ev s +v s ev s +v s ev s out +v s ev s figure 3. simplified schematic theory of operation the ad8225 is a monolithic, three op amp instrumentation amplifier. laser wafer trimming and proprietary circuit tech- niques enable the ad8225 to boast the lowest output offset voltage and drift of any currently available in amp (150 v rti), as well as a higher common-mode voltage range. referring to figure 3, the input buffers consist of super-beta npn transistors q1 and q2, and op amps a1 and a2. the transistors are compensated so that the bias currents are extremely low, typically 100 pa or less. as a result, current noise is also low, at 50 fa/ hz h h h h h h h hhh h h h h
rev. a e12e ad8225 driving a high resolution adc most high precision adcs feature differential analog inputs. differential inputs offer an inherent 6 db improvement in s/n ratio and resultant bit resolution. these advantages are easy to realize using a pair of ad8225s. ad8225s can be configured to drive an adc with differential inputs by using either single-ended or differential inputs to the ad8225s. figure 7 shows the circuit connections for a differen- tial input. a single-ended input may be configured by connecting the negative input terminal to ground. 2 3 2 3 6 6 5 5 ad8225 ad8225 op177 1.25v 4.99k 4.99k 2.7nf 2.7nf 75 75 ad7675 100ksps 5v 16 bits ad780 2.5v rererence +in ein alternate connection for se source figure 7. driver for differential adc the ad7675 adc illustrated in figure 7 is a sar type con verter. when the input is sampled, the internal sample-and-hold ca pacitor is charged to the input voltage level. since the output of the ad 8225 cannot track the instantaneous current surge, a vo ltage glitch develops. to source the momentary current surge, a capacitor is connected from the a/d input terminal to ground. since the ad8225 cannot tolerate greater than approximately 100 pf of capacitance at its output, a 75 series resistor is required at each in amp output to prevent oscillation. using the reference input note in the example in figure 7 that pin 5, the reference input, is d riv en by a voltage source. this is because the reference pin is internally connected to a 15 k resistor, which is carefully trimmed to optimize common-mode rejection. any additional resistance connected to this node will unbalance the bridge network formed by the two 3 k and two 15 k resistors, resulting in an error voltage generated by common-mode voltages at the input pins. ad8225 used as an ekg front end the topology of the instrumentation amplifier has made it the circuit configuration of choice for designers of ekg and other low level biomedical amplifiers. cmrr and common-mode voltage advantages of the instrumentation amplifier are tailor made to meet the challenges of detecting minuscule cardiac generated voltage levels in the presence of overwhelming levels of noise and dc offset voltage. the subtracter circuit of the in amp will extract and amplify low level signals that are virtually obscured by the presence of high common-mode dc and ac potentials. a typical circuit block diagram of an ekg amplifier is shown in figure 8. using discrete op amps in the in amp and gain stages, the signal chain usually includes several filters, high voltage protection, lead-select circuitry, patient lead buffering, and an adc. designers who roll their own instrumentation amplifiers must provide precision custom trimmed resistor networks and well matched op amps. the ad8225 instrumentation amplifier not only replaces all the components shown in the highlighted block in figure 8, but also provides a solution to many of the difficult design problems encountered in ekg front ends. among these are patient gener- ated errors from ac noise sources and errors generated by unequal electrode potentials. alone, these error voltages can exceed the desired qrs complex by orders of magnitude. instrumentation amplifier g = 3 to 10 lead select, hv protection, filtering gain and adc to ta l g = 1000 pat i ent isolation b arrier digital data to system mainframe a1 a2 a3 figure 8. block diagram, ekg monitor front end using discrete components
rev. a ad8225 e13e in the classical three op amp in amp topology shown in figure 8, gain is developed differentially between the two input amplifiers a1 and a2 , sacrificing cmv (common-mode voltage) r ange. the gain of the in amp is typically 10 or less, and an addi tional gain stage increases the overall gain to approximately 1000. gain developed in the input stage results in a trade-off in common- mode voltage range, constraining the ability of the am plifier to tolerate high dc electrode errors. although the ad 8225 is also a three amplifier design, its gain of 5 is developed at the output amplifier, improving the cmv range at the input. using 5v supplies, the cmv range of the ad8225 is from ? 3.4 v to +4 v, compared to ? 3. 1 v to +3. 8 v, a 7% im provement in input headroom over conventional in amps with the same gain. g = 5 ad8225 19.6k 301 100 op77 g = 200 g = 5 ad8225 19.6k 301 100 op77 g = 200 g = 5 ad8225 19.6k 301 100 op77 g = 200 figure 9. ekg monitor front end figure 9 illustrates how an ad8225 may be used in an ekg front end. in a low cost system , the ad8225 can be connected to the patient. if buffers are required, the ad8225 can replace the expensive precision resistor network and op amp. figure 10 shows test waveform s observed from the circuit of figure 9. ch 1 = 2v, ch 2 = 2v, ch 3 = 2v, h = 200ms ra-la 1 la-ll 2 ra-ll 3 figure 10. ekg waveform using circuit of figure 9 benefits of fast slew rates at 5 v/ s, the slew rate of the ad8225 is as fast as many op amp circuits. this is an advantage in systems applications using mu ltiple sensors. for example, an analog multiplexer (see figure 11) may be used to select pairs of leads connected to several sensors. if the ad8225 drives an adc, the acquisition time is constrained by the ability of the in amp to settle to a stable level after a new set of leads is selected. fast slew rates contribute greatly to this function, especially if the difference in input levels is large. ad8225 s1a s1b s2a s2b s3a s3b s4a s4b 0.2v, 2v adg409 1 4 da db ref figure 11. connection to an adg409 analog mux figure 12 illustrates the response of an ad8225 connected to an adg409 analog multiplexer in the circuit shown in figure 11 at two signal levels. two of the four mux inputs are connected to test dc levels. the remaining two are at ground potential so that the output slews as the inputs a0 and a1 are addressed. as can be seen, the output response settles well within 4 s of the applied level. ch 1 = 200mv, ch 2 = 2v, h = 500ns large signal (2v/div) small signal ( 200mv/div) input signal tran- sition figure 12. slew responses after mux selection
rev. a e14e ad8225 evaluation board figure 13 is a schematic of an evaluation board available for the ad8225. the board is shipped with an ad8225 already installed and tested. the user need only connect power and an input to conduct measurements. the supply may be configured for dual a1 2 3 r3 100k * r5 100k * w3 w4 c1 0.1 f c3 0.1 f r4 100 r2 100 +in gnd ein +v s c4 0.1 f output r8 5 4 1 c2 0.1 f w12 ext_ref w13 w11 w14 ev s notes remove w3 and w4 for ac coupling * install for ac coupling +v s gnd ev s c12 10 f, 25v c11 10 f, 25v w7 w6 +v aux ev aux c9 0.1 f 4 6 7 3 2 a1 c10 0.1 f ev aux offset adj r1 10k +v aux r9 5.9k , 1% r10 5.9k , 1% c7 0.1 f c8 0.1 f cs2 j500 240 a cs1 j500 240 a ev aux ad707jn user-supplied 7 6 figure 13. evaluation board schematic or single supplies, and the input may be dc- or ac-coupled. a circuit is provided on the board so that the user can zero the output offset. if desired, a reference may be applied from an external voltage source.
rev. a ad8225 ?5 outline dimensions 8-lead standard small outline package (soic) (rn-8) dimensions shown in millimeters and (inches) 0.25 (0.0098) 0.19 (0.0075) 1.27 (0.0500) 0.41 (0.0160) 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) 85 4 1 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) 0.33 (0.0130) 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
rev. a c02771e0e2/03(a) printed in u.s.a. e16e ad8225 revision history location page 2/03?data sheet changed from rev. 0 to rev. a. updated ordering guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 change to tpc 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 change to tpc 20 caption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 edit to precision v-to-i converter section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 outline dimensions updated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

▲Up To Search▲

Price & Availability of AD8225-EVAL

	To Download AD8225-EVAL Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .