SNOA487C - PDF document

User'sGuide SNOA487C–May2007–RevisedMay2013 AN-1606551012875,551012922UniversalOpAmp EvaluationBoards(SOT-23andSC-70) 1Overview The551012875and551012922UniversalEvaluationBoardsaredesignedtoaidintheevaluationand testingofTexasInstrumentslowvoltage/lowpowerandsomeprecisionoperationalamplifiers.These boardswillaccommodateopampsthatareassembledina6-Pinor5-PinSOT-23andSC-70package, regardlessofthepinorientation. Thisboardisdesignedtouseoneortwoamplifiers.Manydifferentcircuitscanbemadesuchasinverting, non-inverting,anddifferential-IN-differential-OUTamplifiersandlow-pass,high-pass,band-pass,band- reject,ornotchsecond-orderfilters.Theamplifierscanbepoweredwithsingleordualsupplies.These circuitscanbeconfiguredwithoutanymodificationstotheboard;allthatisnecessaryistoselectthe correctresistorsandcapacitors.Theotheroptionalcomponentscanbeleftopenorshorteddependingon theconfigurationdesired. Theseuniversalevaluationboardsaredesignedastwo-layerboards;thetopsideofeachisdesignedfor opampswithapinoutasshowninFigure1. ThebottomsideofeachboardisdesignedforopampswiththepinoutshowninFigure2.Theboardhas beenmanufacturedwithviasconnectingtheequivalentpinsofthetopandbottomamplifiers.For example,Pin1ofIC1AisconnectedtoPin3ofIC2A.Similarlyallotherequivalentpinsofthetopand bottomamplifiersareconnected.Thisallowsforanefficientuseofoneboardtotesttwoamplifiersof differentpackagetypeswhilekeepingthesamecomponentsontheboard;justmakesurethatonlyone amplifierissolderedtothesamepads. Circuitperformanceofthisevaluationboardwillbecomparabletofinalproductiondesigns.Usethis evaluationboardasaguideforgenerallayoutandatooltoaidindevicetestingandcharacterization. SOT-23/SC-70 SOT-23/SC-70 Figure1.ConnectionDiagramforIC1AandIC1B Figure2.ConnectionDiagramforIC2AandIC2B WEBENCHisatrademarkofTexasInstruments. Allothertrademarksarethepropertyoftheirrespectiveowners. 1 SNOA487C–May2007–RevisedMay2013 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated HardwareSetupwww.ti.com 2HardwareSetup 2.1ComponentNotation ThepinsofthefootprintforIC1AareconnectedtotheequivalentpinsforthefootprintofIC2Aandthesame istrueforIC1BandIC2BTherefore,thisapplicationreportwillrefertotheamplifierinIC1AorIC2AasAmpA andtheamplifierinIC1BorIC2BasAmpB.ThesubscriptofthePCBcomponentreferstothespecific amplifier;forexample,R4AisusedforAmpAandR4BforAmpB.Inthisdocument,componentswillbe referredto,asanexample,C3.IfusingAmpAthisreferstocomponentC3A,ifusingAmpBthisrefersto componentC3B. Insomecircuits,aresistorwillbeinstalledwherethePCBislabeledforacapacitororacapacitorwillbe installedwherearesistorislabeled.Forexample,CR6indicatesthatacapacitorshouldbeintheR6 position.RC5meansthataresistorwillbeinstalledintheC5position. 2.2Power PowerisappliedtothepointslabeledVí,GND,andV+.Ifasinglesupplyisused,thenVíshouldbe connectedtoGND.Avirtualground,halfwaybetweenthepositivesupplyvoltageandground,isthe referencepointfortheinputandoutputvoltages.Theoutputvoltageswingsaboveandbelowthisvirtual ground.Single-supplyoperationrequiresthegenerationofthisvirtualground,usuallyatavoltageequalto V+/2.ThecircuitinFigure3canbeusedtogenerateV+/2;R1andR2shouldbeofequalvalues.This junctionalongwithcapacitorC1willformalow-passfilterusedtoeliminateconductednoiseortransients onthepositivesupplyrail. Figure3.SingleSupplyVirtualGround 2.3OpAmp SolderanopamptoeithertheIC1AorIC2Aposition.Ifbuildingacircuitrequiringtwoopamps,solderan additionalopamptoeitherIC1BorIC2B.ThecorrespondingpinoutisshownoneachsideofthePCB. 2.4Bypassing Installthefollowingcapacitors: C6A,C9A,C6B,C9B:0.1µF C7A,C8A,C7B,C8B:1µF 2.5Shutdown TousetheshutdownfeatureoftheamplifierineithertheSOT-23ortheSC-70package,installaresistor atR15andanoptionalcapacitoratC11.TheshutdownvoltageisappliedatS/D-AorS/D-Bdependingon thepackageoftheamplifierbeingused. 2 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards SNOA487C–May2007–RevisedMay2013 (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated www.ti.comCircuitConfigurations 2.6InputandOutput SMAconnectorsareusedfortheinputandoutputofsignals.TheyarelocatedontheedgesofthePCB. 3CircuitConfigurations 3.1Non-InvertingAmplifier C3 Short R4 Short R5 Short R8 InputTermination R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) R14 GainResistor R12 GainResistor Figure4.Non-InvertingAmplifier Where: (1) 3 SNOA487C–May2007–RevisedMay2013 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated CircuitConfigurationswww.ti.com 3.2InvertingAmplifier C3 Short R9 Short R13 Short R8 InputTermination R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) R14 GainResistor R11 GainResistor Figure5.InvertingAmplifier Where: (2) 3.3RegisterCalculations InputImpedance:SetRTtothedesiredinputimpedance.CalculateR8where: (3) TocanceltheinputbiascurrentsetR6tothevaluecalculatedwiththefollowingformula: (4) 3.4ActiveFilterApplications BothSallen-KeyandMultipleFeedbackfilterscanbebuiltonthisPCB.Todesignafilter,usethe WEBENCH™toolatwww.ti.com.Performanceathighfrequenciesislimitedtothegainbandwidthproduct oftheamplifier,butwithinthisfrequencyrange,theseactivefilterscanachieveverygoodaccuracy,iflow- toleranceresistorsandcapacitorareused. 4 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards SNOA487C–May2007–RevisedMay2013 (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated www.ti.comCircuitConfigurations 3.5Sallen-KeyLow-PassFilter C3 Short R13 Short R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) R8 InputTermination SetthefollowingasdeterminedusingWEBENCH:R4,R5,CR6,R14,R12 Figure6.Sallen-KeyLow-PassFilter 3.6MultipleFeedbackLow-PassFilter Note:Ifneeded,aninputterminationresistorwillneedtobesolderedontotheSMAconnectorbetween thesignalpinandthegroundpin. R6 Short R13 Short R9 Short C5 Short R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) SetthefollowingasdeterminedusingWEBENCH:RC3,CR8,R4,R11,C10 Figure7.MultipleFeedbackLow-PassFilter 5 SNOA487C–May2007–RevisedMay2013 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated CircuitConfigurationswww.ti.com 3.7Sallen-KeyHigh-PassFilter C3 Short R13 Short R14 Short R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) R8 InputTermination SetasdeterminedusingWEBENCH:CR4,CR5,RC5,R6 Figure8.Sallen-KeyHigh-PassFilter 3.8MultipleFeedbackHigh-PassFilter Note:Ifneeded,aninputterminationresistorwillneedtobesolderedontotheSMAconnectorbetween thesignalpinandthegroundpin. R9 Short R4 Short R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) SetthefollowingasdeterminedusingWEBENCH:C3,R8,C5,CR11,R14 Figure9.MultipleFeedbackHigh-PassFilter 6 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards SNOA487C–May2007–RevisedMay2013 (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated www.ti.comCircuitConfigurations 3.9Sallen-KeyBand-PassFilter C3 Short R13 Short R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) R8 InputTermination SetasdeterminedusingWEBENCH:R4,C4,CR5,R6,RC5,R14,R12 Figure10.Sallen-KeyBand-PassFilter 3.10MultipleFeedbackBand-PassFilter Note:Ifneeded,aninputterminationresistorwillneedtobesolderedontotheSMAconnectorbetween thesignalpinandthegroundpin. R6 Short R13 Short R9 Short R4 Short R7 Outputseriesresistance(usedformatchingtransmissionlinesorisolation) SetthefollowingasdeterminedusingWEBENCH:RC3,R8,C5,CR11,R14 Figure11.MultipleFeedbackBand-PassFilter 7 SNOA487C–May2007–RevisedMay2013 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated ApplicationsUsingTwoAmplifierswww.ti.com 4ApplicationsUsingTwoAmplifiers 4.1Two-AmplifierFilters FiltersusingtwoamplifierscanbebuiltbyconnectingtheoutputofAmpAtotheinputofAmpB. 4.2Single-EndedtoDifferentialConversion ThecircuitinFigure12willconvertasingle-endedsignaltoadifferentialsignal.Thisisdonebyusingthe combinationofaninvertingamplifierandanon-invertingamplifier.Eachamplifiergeneratesoutputsignals ofequalmagnitudebutofoppositepolarity.Thistopologyisusefulinapplicationswherethesignalsource issingle-ended,buttheADCrequiresadifferentialinput.Theboardwillneedtobemodifiedby connectingInputAtoInputBwithajumperwire. Figure12.Single-EndedtoDifferentialConversion 8 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards SNOA487C–May2007–RevisedMay2013 (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated www.ti.comApplicationsUsingTwoAmplifiers 4.3DifferentialInput,DifferentialOutput,Non-Inverting Combiningtwonon-invertingamplifierswithacommonfeedbacknetwork,asshowninFigure13,formsa non-invertingamplifierwithadifferentialinputandadifferentialoutput.Throughtheinherentcancellation ofthetwoopampcommon-modeerrorsignalsthisconfigurationfullyexploitsthenoisereductionbenefits ofCMRR.Inadditiontheoutputvoltageswingisdoubledanddependingontheopampused,the bandwidthandslewratemayalsobeincreased,whilemaintainingtheoriginalgainbandwidth specification. Figure13.DifferentialInput,DifferentialOutput,Non-Inverting 9 SNOA487C–May2007–RevisedMay2013 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated 551012875-001Schematicwww.ti.com 5551012875-001Schematic Figure14.551012875-001Schematic 10 AN-1606551012875,551012922UniversalOpAmpEvaluationBoards SNOA487C–May2007–RevisedMay2013 (SOT-23andSC-70) SubmitDocumentationFeedback Copyright©2007–2013,TexasInstrumentsIncorporated