ina321

INA321INA2321 SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006microPower, Single-Supply, CMOSInstrumentation AmplifierFEATURESDLOW QUIESCENT CURRENT: 40µA/channelDDDDDDDDDShut Down: < 1µAHIGH GAIN ACCURACY: G = 5, 0.02%,2ppm/°CGAIN SET WITH EXTERNAL RESISTORSLOW OFFSET VOLTAGE: ±200µVHIGH CMRR: 94dBLOW BIAS CURRENT: 10pABANDWIDTH: 500kHz, G = 5V/VRAIL-TO-RAIL OUTPUT SWING: (V+) − 0.02VWIDE TEMPERATURE RANGE:−55°C to +125°CSINGLE VERSION IN MSOP-8 PACKAGE ANDDUAL VERSION IN TSSOP-14 PACKAGEAPPLICATIONSDINDUSTRIAL SENSOR AMPLIFIERS:DDDDDDDDBridge, RTD, Thermistor, PositionPHYSIOLOGICAL AMPLIFIERS:ECG, EEG, EMGA/D CONVERTER SIGNAL CONDITIONINGDIFFERENTIAL LINE RECEIVERS WITH GAINFIELD UTILITY METERSPCMCIA CARDSCOMMUNICATION SYSTEMSTEST EQUIPMENTAUTOMOTIVE INSTRUMENTATIONCMRRvsFREQUENCY120DESCRIPTIONThe INA321 family is a series of rail-to-rail output,micropower CMOS instrumentation amplifiers that offerwide-range, single-supply, as well as bipolar-supplyoperation. The INA321 family provides low-cost, low-noiseamplification of differential signals with micropowercurrent consumption of 40µA. When shutdown, theINA321 has a quiescent current of less than 1µA.Returning to normal operations within microseconds, theshutdown feature makes the INA321 optimal forlow-power battery or multiplexing applications.Configured internally for 5V/V gain, the INA321 offersexceptional flexibility with user-programmable externalgain resistors. The INA321 reduces common-mode errorover frequency and with CMRR remaining high up to 3kHz,line noise and line harmonics are rejected.The low-power design does not compromise on bandwidthor slew rate, making the INA321 ideal for driving sampleAnalog-to-Digital (A/D) converters as well asgeneral-purpose applications. With high precision, lowcost, and small packaging, the INA321 outperformsdiscrete designs, while offering reliability andperformance.CMRR(dB)100INA32180NearestCompetition6010xImprovement4010100Frequency(Hz)1k10kR1160kΩREFA1RG160kΩR240kΩ40kΩVIN−VIN+A3A2VOUTGain=5+5(R2/R1)VOUT=(VIN+−VIN−)•GainV−ShutdownV+Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of TexasInstrumentssemiconductor products and disclaimers thereto appears at the end of this data sheet.All trademarks are the property of their respective owners.PRODUCTION DATA information is current as of publication date. Productsconform to specifications per the terms of Texas Instruments standard warranty.Production processing does not necessarily include testing of all parameters.Copyright  2000-2006, Texas Instruments Incorporatedwww.ti.comINA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006ABSOLUTE MAXIMUM RATINGS(1)Supply Voltage, V+ to V−. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5VSignal Input Terminals Voltage(2). . . (V−) − (0.5V) to (V+) + (0.5V)Current(2). . . . . . . . . . . . . . . . . . . . . 10mAOutput Short-Circuit(3). . . . . . . . . . . . . . . . . . . . . . . . . . ContinuousOperating Temperature. . . . . . . . . . . . . . . . . . . . . . −65°C to +150°CStorage Temperature. . . . . . . . . . . . . . . . . . . . . . . . −65°C to +150°CJunction Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C(1)Stresses above these ratings may cause permanent damage.Exposure to absolute maximum conditions for extended periodsmay degrade device reliability. These are stress ratings only, andfunctional operation of the device at these or any other conditionsbeyond those specified is not supported.(2)Input terminals are diode-clamped to the power-supply rails.Input signals that can swing more than 0.5V beyond the supplyrails should be current limited to 10mA or less.(3)Short-circuit to ground, one amplifier per package.ELECTROSTATICDISCHARGE SENSITIVITYThis integrated circuit can be damaged by ESD. Texas Instrumentsrecommends that all integrated circuits be handled with appropriateprecautions. Failure to observe proper handling and installationprocedures can cause damage.ESD damage can range from subtle performance degradation tocomplete device failure. Precision integrated circuits may be moresusceptible to damage because very small parametric changes couldcause the device not to meet its published specifications.PACKAGE/ORDERING INFORMATION(1)PRODUCTSINGLEINA321EPACKAGE-LEADPACKAGEDESIGNATORSPECIFIEDTEMPERATURERANGE−55°C to +125°CPACKAGEMARKINGORDERINGNUMBERTRANSPORTMEDIA, QUANTITY″″″MSOP-8″″″DGK″″″″″″C21″″″INA321E/250INA321E/2K5INA321EA/250INA321EA/2K5INA2321EA/250INA2321EA/2K5Tape and Reel, 250Tape and Reel, 2500Tape and Reel, 250Tape and Reel, 3000Tape and Reel, 250Tape and Reel, 2500INA321EADUALINA2321EAMSOP-8DGK−55°C to +125°CC21TSSOP-14PW−55°C to +125°CINA2321EA(1)For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet.PIN CONFIGURATIONSTop ViewINA2321INA321RGVIN−VIN+V−1234MSOP−8(E,EA)8765ShutdownV+VOUTREFRGAVIN−AVIN+AV−VIN+BVIN−BRGB1234567Dual,TSSOP−14(EA)141312111098ShutdownAVOUTAREFAV+REFBVOUTBShutdownB2INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V BOLDFACE limits apply over the specified temperature range, TA = −555C to +1255C.At TA = +25°C, RL = 25kΩ, G = 25, and IA common = VS/2, unless otherwise noted.INA321EPARAMETERINPUTInput Offset Voltage, RTIOver Temperaturevs Temperaturevs Power SupplyOver TemperatureLong-Term StabilityInput ImpedanceInput Common-Mode RangeCommon-ModeRejectionOver TemperatureCrosstalk, DualINPUT BIAS CURRENTBias CurrentOffset CurrentNOISE, RTIVoltage Noise: f = 10Hzf = 100Hzf = 1kHzf = 0.1Hz to 10HzCurrent Noise: f = 1kHzGAIN(1)Gain Equation, Externally SetRange of GainGain Errorvs TemperatureNonlinearityOver TemperatureOUTPUTOutput Voltage Swing from Rail(2, 5)Over TemperatureCapacitance Load DriveShort-Circuit Current+ISC−ISCG ≥ 105050See Typical Characteristic(3)816∗mA25∗*∗∗mVmVpFG = 5G = 25, VS = 5V, VO = 0.05 to 4.95G > 55±0.02±2±0.001±0.002IBIOSenRS = 0Ω500190100203G = 5 + 5 (R2/R1)1000±0.1±10±0.010±0.015∗∗*∗*∗∗∗∗∗∗∗∗*∗*V/V%ppm/°C% of FS% of FSnV/√HznV/√HznV/√HzµVPPfA/√Hz±0.5±0.5±10±10∗∗∗∗pApAVS = 2.7VVS = 5VCMRRVS = 5V, VCM = 0.55V to 3.8VVS = 5V, VCM = 0.55V to 3.8VVS = 2.7V, VCM = 0.35V to 1.5V0.350.5590779411094±0.41013 || 31.53.8∗∗8075∗∗∗VOSdVOS/dTPSRRVS = +2.7V to +5.5VVS = +5V±0.2±7±50±200±220∗∗∗∗±0.5±2.2*∗∗*∗12.5mVmVµV/°CµV/VµV/VµV/monthΩ || pFVVdBdBdBdBINA321EAINA2321EAMAXMINTYPMAXUNITCONDITIONSMINTYPNOTE:∗ Specification is same as INA321E.(1)Does not include errors from external gain setting resistors.(2)Output voltage swings are measured between the output and power-supply rails.(3)See typical characteristic Percent Overshoot vs Load Capacitance.(4)See typical characteristic Shutdown Voltage vs Supply Voltage.(5)Output does not swing to positive rail if gain is less than 10.3INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V (continued)BOLDFACE limits apply over the specified temperature range, TA = −555C to +1255C.At TA = +25°C, RL = 25kΩ, G = 25, and IA common = VS/2, unless otherwise noted.INA321EPARAMETERFREQUENCY RESPONSEBandwidth, −3dBSlew RateSettling Time, 0.1%0.01%Overload RecoveryPOWER SUPPLYSpecified Voltage RangeOperating Voltage RangeQuiescent CurrentOver TemperatureShutdown Quiescent CurrentTEMPERATURE RANGESpecified RangeOperating/Storage RangeThermal ResistanceqJAMSOP-8, TSSOP-14Surface-Mount−55−65150+125+150∗∗∗∗∗°C°C°C/WISDper Channel, VSD > 0.8(4)0.01IQper Channel, VSD > 2.5(4)+2.7+2.5 to +5.54060701∗+5.5∗∗∗∗*∗∗VVµAµAµA50% Input Overload G = 25BWSRtSG = 5 VS = 5V, G = 25G = 5, CL = 50pF, VO = 2V step5000.48122∗∗∗∗∗kHzV/µsµsµsµsINA321EAINA2321EAMAXMINTYPMAXUNITCONDITIONSMINTYPNOTE:∗ Specification is same as INA321E.(1)Does not include errors from external gain setting resistors.(2)Output voltage swings are measured between the output and power-supply rails.(3)See typical characteristic Percent Overshoot vs Load Capacitance.(4)See typical characteristic Shutdown Voltage vs Supply Voltage.(5)Output does not swing to positive rail if gain is less than 10.4INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006TYPICAL CHARACTERISTICS At TA = +25°C, VS = 5V, VCM =1/2VS, RL = 25kΩ, and CL = 50pF, unless otherwise noted.GAINvsFREQUENCY80706050Gain(dB)403020100−10−20101001k10k100k1M10MFrequency(Hz)POWER−SUPPLYREJECTIONRATIOvsFREQUENCY100MaximumOutputVoltage(VPP)908070PSRR(dB)60504030201001101001k10k100kFrequency(Hz)NOISEvsFREQUENCY10k1006543210100010Gain=500CMRR(dB)Gain=100Gain=25Gain=510080604020120COMMON−MODEREJECTIONRATIOvsFREQUENCY1001kFrequency(Hz)10k100kMAXIMUMOUTPUTVOLTAGEvsFREQUENCYVS=5.5VVS=5.0VVS=2.7V1k10k100k1M10MFrequency(Hz)0.1HzTO10HzVOLTAGENOISEVNOISE(nV/√Hz)INoise(fA/√Hz)1k101001101101001k10kFrequency(Hz)0.1100k10µv/div1s/div5INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006TYPICAL CHARACTERISTICS (continued)At TA = +25°C, VS = 5V, VCM =1/2VS, RL = 25kΩ, and CL = 50pF, unless otherwise noted.OUTPUTSWINGvsLOADRESISTANCE25OutputReferredtoGround(V)65COMMON−MODEINPUTRANGEvsREFERENCEVOLTAGE20Swing−to−Rail(mV)OutsideofNormalOperation4321015ToPositiveRail10ToNegativeRailREFIncreasing50020k40k60k80k100kRLOAD(Ω)QUIESCENTCURRENTANDSHUTDOWNCURRENTvsPOWERSUPPLY50454035IQ(µA)3025201510502.533.544.555.5SupplyVoltage(V)SHORT−CIRCUITCURRENTvsPOWERSUPPLY20ISC+1520ISC(mA)10ISC(mA)3025ISDIQ500450400350ISD(nA)300250200150100500IQ(µA)012345InputCommon−ModeVoltage(V)QUIESCENTCURRENTANDSHUTDOWNCURRENTvsTEMPERATURE605550454035302520151050−75−50600500IQ400300200ISD−2502550751001251000150ISD(nA)Temperature(_C)SHORT−CIRCUITCURRENTvsTEMPERATUREISC+1510ISC−5502.533.544.555.5SupplyVoltage(V)0−75−50−25025ISC−5075100125150Temperature(_C)6INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006TYPICAL CHARACTERISTICS (continued)At TA = +25°C, VS = 5V, VCM =1/2VS, RL = 25kΩ, and CL = 50pF, unless otherwise noted.SMALL−SIGNALSTEPRESPONSE(G=5)SMALL−SIGNALSTEPRESPONSE(G=100)100mV/div10µs/divSMALL−SIGNALSTEPRESPONSE(G=5,CL=1000pF)50mV/div50µs/divSMALL−SIGNALSTEPRESPONSE(G=100,CL=1000pF)100mV/div10µs/divSMALL−SIGNALSTEPRESPONSE(G=100,CL=5000pF)50mV/div50µs/divLARGE−SIGNALSTEPRESPONSE(G=25,CL=50pF)50mV/div50µs/div1V/div50µs/div7INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006TYPICAL CHARACTERISTICS (continued)At TA = +25°C, VS = 5V, VCM =1/2VS, RL = 25kΩ, and CL = 50pF, unless otherwise noted.SETTLINGTIMEvsGAIN1009080SettlingTime(µs)706050403020100110Gain(V/V)SHUTDOWNVOLTAGEvsSUPPLYVOLTAGE32.5NormalOperationModeShutdown(V)21.51ShutdownMode0.5PartDrawsBelow1µAQuiescentCurrent02.333.544.555.51V/divOperationinthisRegionisnotRecommended10010000100.1%10Output2VPPDifferentialInputDrive0.01%Overshoot(%)60504030PERCENTOVERSHOOTvsLOADCAPACITANCEOutput100mVPPDifferentialInputDriveG=5G=25201001k10kLoadCapacitance(pF)SHUTDOWNTRANSIENTBEHAVIORVSDVOUT50µs/divSupplyVoltage(V)OFFSETVOLTAGEDRIFTPRODUCTIONDISTRIBUTION2018PercentageofAmplifiers(%)20PercentageofAmplifiers(%)−1.0−0.9−0.8−0.7−0.6−0.5−0.4−0.3−0.2−0.1OFFSETVOLTAGEPRODUCTIONDISTRIBUTION2516141210864215105000.10.20.30.40.50.60.70.80.91.00−20−18−16−14−12−10−8−6−4−2024681012141618OffsetVoltage(mV)OffsetVoltageDrift(µV/_C)820INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006TYPICAL CHARACTERISTICS (continued)At TA = +25°C, VS = 5V, VCM =1/2VS, RL = 25kΩ, and CL = 50pF, unless otherwise noted.SLEWRATEvsTEMPERATURE110kINPUTBIASCURRENTvsTEMPERATURE0.8InputBiasCurrent(pA)−50−250255075100125150SlewRate(V/µs)1k0.61000.4100.200−750.1−75−50−250255075100125150Temperature(_C)CROSSTALKvsFREQUENCY120100OutputVoltage(V)Crosstalk(dB)8060402005Temperature(_C)OUTPUTVOLTAGESWINGvsOUTPUTCURRENT4+125°C3+25°C−55_C2+125°C1+25°C−55_C00.11101001k10k100k1M024681012141618202224Frequency(Hz)OutputCurrent(mA)9INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006APPLICATIONS INFORMATIONThe INA321 is a modified version of the classic two op ampinstrumentation amplifier, with an additional gain amplifier.Figure 1 shows the basic connections for the operation ofthe INA321 and INA2321. The power supply should becapacitively decoupled with 0.1µF capacitors as close tothe INA321 as possible for noisy or high-impedanceapplications.The output is referred to the reference terminal, whichmust be at least 1.2V below the positive supply rail.OPERATING VOLTAGEThe INA321 family is fully specified over a supply range of+2.7V to +5.5V, with key parameters assured over thetemperature range of −55°C to +125°C. Parameters thatvary significantly with operating conditions, such as loadconditions or temperature, are shown in the TypicalCharacteristics.The INA321 may be operated on a single supply. Figure 2shows a bridge amplifier circuit operated from a single +5Vsupply. The bridge provides a small differential voltageriding on an input common-mode voltage.G=5+5(R2/R1)ShortVOUTtoRGforG=5RG15160kΩ40kΩ160kΩDESIREDGAIN(V/V)51050100R1R2R1R2OPENSHORT100kΩ100kΩ10kΩ90kΩΩ10k190kΩREFVIN−VIN+23A140kΩA3A26VO=((VIN+)−(VIN−))•G874Alsodrawninsimplifiedform:V+VIN+REF35278INA32114V−RG6VOUTShutdownShutdown0.1µFV+(ForSingleSupply)V−0.1µFVIN−Figure 1. Basic Connections+5VBridgeSensorVIN+REF(1)VIN−352V+7INA321Shutdown816VOUT4V−RGNOTE:(1)REFshouldbeadjustedforthedesiredoutputlevel,keepinginmindthatthevalueofREFaffectsthecommon−modeinputrange.SeeTypicalCharacteristics.Figure 2. Bridge Amplifier of the INA32110INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006SETTING THE GAINThe ratio of R2 to R1, or the impedance between pins 1, 5,and 6, determines the gain of the INA321. With aninternally set gain of 5, the INA321 can be programmed forgains greater than 5 according to the following equation:G = 5 + 5 (R2/R1)The INA321 is designed to provide accurate gain, with gainerror assured to be less than 0.1%. Setting gain withmatching TC resistors will minimize gain drift. Errors fromexternal resistors will add directly to the gain error, andmay become dominant error sources.Figure 3 shows how bias current path can be provided inthe cases of microphone applications, thermistorapplications, ground returns, and dc-coupled resistivebridge applications.V+VIN+3Microphone,Hydrophone,etc.REF57Shutdown8INA32114V−RG6VOUTVIN−247kΩVB(1)INPUT COMMON-MODE RANGEThe upper limit of the common-mode input range is set bythe common-mode input range of the second amplifier, A2,to 1.2V below positive supply. Under most conditions, theamplifier operates beyond this point with reducedperformance. The lower limit of the input range is boundedby the output swing of amplifier A1, and is a function of thereference voltage according to the following equation:VOA1 = 5/4 VCM — 1/4 VREF(See Typical Characteristics for Input Common-ModeRange vs Reference Voltage).TransformerV+VIN+REF357Shutdown8INA32114V−6VOUTVIN−2VB(1)REFERENCEThe reference terminal defines the zero output voltagelevel. In setting the reference voltage, the common-modeinput of A3 should be considered according to the followingequation:VOA2 = VREF + 5 (VIN+ − VIN−)For optimal operation, VOA2 should be less thanVDD − 1.2V.The reference pin requires a low-impedance connection.As little as 160Ω in series with the reference pin willdegrade the CMRR to 80dB. The reference pin may beused to compensate for the offset voltage (see OffsetTrimming section). The reference voltage level alsoinfluences the common-mode input range (seeCommon-Mode Input Range section).BridgeAmplifierVEXV+BridgeSensorCenter−tapRGprovidesbiascurrentreturnVIN+REFShutdown8357INA32114V−RGBridgeresistanceprovidesbiascurrentreturn6VOUTVIN−2NOTE:(1)VBisbiasvoltagewithincommon−moderange,dependentonREF.INPUT BIAS CURRENT RETURNWith a high input impedance of 1013Ω, the INA321 is idealfor use with high-impedance sources. The input biascurrent of less than 10pA makes the INA321 nearlyindependent of input impedance and ideal for low-powerapplications.For proper operation, a path must be provided for inputbias currents for both inputs. Without input bias currentpaths, the inputs will float to a potential that exceedscommon-mode range and the input amplifier will saturate.Figure 3. Providing an Input Common-Mode PathWhen differential source impedance is low, the biascurrent return path can be connected to one input. Withhigher source impedance, two equal resistors will providea balanced input. The advantages are lower input offsetvoltage due to bias current flowing through the sourceimpedance and better high-frequency gain.11INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006OUTPUT BUFFERINGThe INA321 is optimized for a load impedance of 10kΩ orgreater. For higher output current the INA321 can bebuffered using the OPA340, as shown in Figure 4. TheOPA340 can swing within 50mV of the supply rail, drivinga 600Ω load. The OPA340 is available in the tiny MSOP-8package.+5Vlow output impedance at high frequencies makes itsuitable for directly driving Capacitive Digital-to-Analog(CDAC) input A/D converters, as shown in Figure 5.+5VVIN+REFVIN−0.1µFV+7INA32114V−RGShutdown86VOUTOPA340VOUT0.1µF352V+7INA321Shutdown816VOUTADS7818orADS782212−Bits4V−RGfS<100kHzVIN+REFVIN−352Figure 5. INA321 Directly Drives aCapacitive-Input, A/D ConverterOFFSET TRIMMINGThe INA321 is laser-trimmed for low offset voltage. In theevent that external offset adjustment is required, the offsetcan be adjusted by applying a correction voltage to thereference terminal. Figure 6 shows an optional circuit fortrimming offset voltage. The voltage applied to the REFterminal is added to the output signal. The gain from REFto VOUT is +1. An op-amp buffer is used to provide lowimpedance at the REF terminal to preserve goodcommon-mode rejection.V+VIN+378INA32114V−RG6VOUTShutdownFigure 4. Output Buffering Circuit. Able to driveloads as low as 600Ω.SHUTDOWN MODEThe shutdown pin of the INA321 is nominally connected toV+. When the pin is pulled below 0.8V on a 5V supply, theINA321 goes into sleep mode within nanoseconds. Foractual shutdown threshold, see the Typical Characteristiccurve, Shutdown Voltage vs Supply Voltage. Drawing lessthan 1µA of current, and returning from sleep mode inmicroseconds, the shutdown feature is useful for portableapplications. Once in sleep-mode, the amplifier has highoutput impedance, making the INA321 suitable formultiplexing.REF(1)5VIN−2RAIL-TO-RAIL OUTPUTA class AB output stage with common-source transistorsis used to achieve rail-to-rail output for gains of 10 orgreater. For resistive loads greater than 25kΩ, the outputvoltage can swing to within a few millivolts of the supply railwhile maintaining low gain error. For heavier loads andover temperature, see the Typical Characteristic curve,Output Voltage Swing vs Output Current. The INA321’sOPA336AdjustableVoltageNOTE: (1) REF should be adjusted for the desired output level.The value of REF affects the common−mode input range.Figure 6. Optional Offset Trimming Voltage12INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006INPUT PROTECTIONDevice inputs are protected by ESD diodes that willconduct if the input voltages exceed the power supplies bymore than 500mV. Momentary voltages greater than500mV beyond the power supply can be tolerated if thecurrent through the input pins is limited to 10mA. This iseasily accomplished with input resistor RLIM, as shown inFigure 7. Many input signals are inherently current-limitedto less than 10mA; therefore, a limiting resistor is notrequired.V+RLIMVIN+IOVERLOAD10mAmaxVIN−RLIMREF35278INA32114V−RG6VOUTShutdownCalculation of the worst-case expected offset would be asfollows:Adjusted VOS = Maximum specified VOS +(power-supply variation) • PSRR +(common-mode variation) • CMRRVOS = 0.5mV + (1.7V • 200µV) + (0.65V • 30µV)= ±0.860mVHowever, the typical value will be smaller, as seen in theTypical Characteristics.FEEDBACK CAPACITOR IMPROVES RESPONSEFor optimum settling time and stability withhigh-impedance feedback networks, it may be necessaryto add a feedback capacitor across the feedback resistor,RF, as shown in Figure 8. This capacitor compensates forthe zero created by the feedback network impedance andthe INA321’s RG-pin input capacitance (and any parasiticlayout capacitance). The effect becomes more significantwith higher impedance networks. Also, RX and CL can beadded to reduce high-frequency noise.V+3INA321Figure 7. Input ProtectionOFFSET VOLTAGE ERROR CALCULATIONThe offset voltage (VOS) of the INA321E is specified at amaximum of 500µV with a +5V power supply and thecommon-mode voltage at VS/2. Additional specificationsfor power-supply rejection and common-mode rejectionare provided to allow the user to easily calculateworst-case expected offset under the conditions of a givenapplication.Power-Supply Rejection Ratio (PSRR) is specified inµV/V. For the INA321, worst-case PSRR is 200µV/V,which means for each volt of change in power supply, theoffset may shift up to 200µV. Common-Mode RejectionRatio (CMRR) is specified in dB, which can be convertedto µV/V using the following equation:CMRR (in µV/V) = 10[(CMRR in dB)/—20] • 106For the INA321, the worst-case CMRR over the specifiedcommon-mode range is 90dB (at G = 25) or about 30µV/V.This means that for every volt of change in common-mode,the offset will shift less than 30µV.These numbers can be used to calculate excursions fromthe specified offset voltage under different applicationconditions. For example, an application might configurethe amplifier with a 3.3V supply with 1V common-mode.This configuration varies from the specified configuration,representing a 1.7V variation in power supply (5V in theoffset specification versus 3.3V in the application) and a0.65V variation in common-mode voltage from thespecified VS/2.VIN+7Shutdown8CIN1RG6REF5RXVOUTCLVIN−24V−RINRFCFRIN•CIN=RF•CFWhereCINisequaltotheINA321inputcapacitance(approximately3pF)plusanyparasticlayoutcapacitance.Figure 8. Feedback Capacitor Improves DynamicPerformanceIt is suggested that a variable capacitor be used for thefeedback capacitor since input capacitance may varybetween instrumentation amplifiers, and layoutcapacitance is difficult to determine. For the circuit shownin Figure 8, the value of the variable feedback capacitorshould be chosen by the following equation:RIN • CIN = RF • CFwhere CIN is equal to the INA321’s RG-pin inputcapacitance (typically 3pF) plus the layout capacitance.The capacitor can be varied until optimum performance isobtained.13INA321INA2321www.ti.com SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006APPLICATION CIRCUITSMedical ECG ApplicationsFigure 9 shows the INA321 configured to serve as alow-cost ECG amplifier, suitable for moderate accuracyheart-rate applications such as fitness equipment. Theinput signals are obtained from the left and right arms of thepatient. The common-mode voltage is set by two 2MΩ resistors. This potential, through a buffer, provides anoptional right leg drive. Filtering can be modified to suitapplication needs by changing the capacitor value of theoutput filter.Low-Power, Single-Supply Data AcquisitionSystemsRefer to Figure 5 to see the INA321 configured to drive anADS7818. Functioning at frequencies of up to 500kHz, theINA321 is ideal for low-power data acquisition.VROPA3360.1µFV+LeftArmShield100kΩVIN+3REF100kΩRightArm+5V2MΩ2kΩVR=+2.5V2kΩOPA3362MΩVIN−524V−RG78INA3211VR1MΩ61.6nFShutdown1MΩ1MΩ10kΩ10kΩOPA336VOUTPUTShieldDrive10kΩ390kΩ100kΩOPA336VRRightLegFigure 9. Simplified ECG Circuit for Medical Applications14PACKAGE OPTION ADDENDUM

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Orderable DeviceINA2321EA/250INA2321EA/250G4INA2321EA/2K5INA2321EA/2K5G4INA321E/250INA321E/250G4INA321E/2K5INA321E/2K5G4INA321EA/250INA321EA/250G4INA321EA/2K5INA321EA/2K5G4

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ACTIVEACTIVEACTIVEACTIVEACTIVEACTIVEACTIVEACTIVEACTIVEACTIVEACTIVEACTIVE

Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)Green (RoHS& no Sb/Br)

CU NIPDAULevel-1-260C-UNLIMCU NIPDAULevel-1-260C-UNLIMCU NIPDAULevel-1-260C-UNLIMCU NIPDAULevel-1-260C-UNLIMCU NIPDAUAGLevel-2-260C-1 YEARCU NIPDAUAGLevel-2-260C-1 YEARCU NIPDAUAGLevel-2-260C-1 YEARCU NIPDAUAGLevel-2-260C-1 YEARCU NIPDAUAGLevel-2-260C-1 YEARCU NIPDAUAGLevel-2-260C-1 YEARCU NIPDAUAGLevel-2-260C-1 YEARCU NIPDAUAGLevel-2-260C-1 YEAR

The marketing status values are defined as follows:ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.PREVIEW: Device has been announced but is not in production. Samples may or may not be available.OBSOLETE: TI has discontinued the production of the device.

(2)

Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availabilityinformation and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

Addendum-Page 1

PACKAGE OPTION ADDENDUM

www.ti.com

9-Dec-2010

Pb-Free (RoHS): TI's terms \"Lead-Free\" or \"Pb-Free\" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement thatlead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used betweenthe die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.

Green (RoHS & no Sb/Br): TI defines \"Green\" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weightin homogeneous material)

(3)

MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on informationprovided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken andcontinues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

Addendum-Page 2

PACKAGEMATERIALSINFORMATION

www.ti.com

19-Aug-2010

TAPEANDREELINFORMATION

*Alldimensionsarenominal

Device

PackagePackagePinsTypeDrawingTSSOPTSSOPMSOPMSOPMSOPMSOP

PWPWDGKDGKDGKDGK

14148888

SPQ

ReelReelA0DiameterWidth(mm)(mm)W1(mm)180.0330.0180.0330.0180.0330.0

12.412.412.412.412.412.4

6.96.95.35.35.35.3

B0(mm)5.65.63.43.43.43.4

K0(mm)1.61.61.41.41.41.4

P1(mm)8.08.08.08.08.08.0

WPin1(mm)Quadrant12.012.012.012.012.012.0

Q1Q1Q1Q1Q1Q1

INA2321EA/250INA2321EA/2K5INA321E/250INA321E/2K5INA321EA/250INA321EA/2K5

250250025025002502500

PackMaterials-Page1

PACKAGEMATERIALSINFORMATION

www.ti.com

19-Aug-2010

*Alldimensionsarenominal

DeviceINA2321EA/250INA2321EA/2K5INA321E/250INA321E/2K5INA321EA/250INA321EA/2K5

PackageType

TSSOPTSSOPMSOPMSOPMSOPMSOP

PackageDrawing

PWPWDGKDGKDGKDGK

Pins14148888

SPQ250250025025002502500

Length(mm)

190.5346.0190.5346.0190.5346.0

Width(mm)212.7346.0212.7346.0212.7346.0

Height(mm)

31.829.031.829.031.829.0

PackMaterials-Page2

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