SAR-ADC-教程之三

1PresentedbyFrankOhnhäuser,TexasInstrumentsTraining10:Analog-to-DigitalConverter(ADC)ConverterTypes2Training101.Designan8bitPipelineADCwith2bitresolutionperstage.–Howmanycomparatorsandbuffersarerequired.–Whatisthemaximumconversionrateata20MHzclock,whatisthethroughputrate.3Training104x2bitADC:4x3comparators+3buffer=15activecircuitsConversionrate=Clockrate(20MHz)Throughputrate=fclk/4=5MHz4Training102.Calculatethestatesofanunipolar5bitSARconverter,whichhasfull-scalerangeof4V.Theanaloginputvoltageis2.4V.–Howmanycomparatorsandbuffersarerequired.–Whatisthemaximumconversionrateata20MHzclock,whatisthethroughputrate.5Training106Training103.Adelta-sigmamodulatorwith10MHzclockshowstheperformancebelow.Itisusedforthecurrentmeasurementinamotorcontrolapplication.Twodigitalfiltersneedtobedefined.-Oneforover-currentprotectioninfailuremodes,wheretheover-currentneedstobedetectedwithin5μs.Whichfiltershouldbechosen(orderandOSR)andwhatisthemaximumresolution.-Thesecondfiltershouldgeneratea12bitvalue.Whichfiltershouldbeused(orderandOSR).02468101214161101001000OSRENOB(bit)sinc3sinc2sinc0246810120246810settlingtime(us)ENOB(bit)sinc3sinc2sinc17Training10Filterforover-currentprotectioninfailuremodes,wheretheover-currentneedstobedetectedwithin5μs.Whichfiltershouldbechosen(orderandOSR)andwhatisthemaximumresolution.0246810120246810settlingtime(us)ENOB(bit)sinc3sinc2sinc1Order:m=sinc3OSR=5us/(100ns·3)OSR=16ResolutionENOB=7.8bit8Training10Thesecondfiltershouldgeneratea12bitvalue.Whichfiltershouldbeused(orderandOSR).02468101214161101001000OSRENOB(bit)sinc3sinc2sincOrder:m=sinc3OSR=649Training104.ApplicationMotorControl:WhichistherightADCtypeIGBTsACmotorCurrentSensorIVCurrentSensorIWPositioningSensoratmotorResolverorEncoderPositioningSensoratload(Encoder)AnalogInputACsupplyDCLinkSensorTemperatureCurrentIUCurrentIVCurrentIWDCLinkVoltageAnalogInputVoltageCurrentSensorIU10Training10Themotorcontrolloopisregulatedwith16kHz.Fortheregulation,thecurrentatthephaseandthepositionofthemotorneedstobemeasured.FromtimetotimetheDClinkvoltageandthetemperatureneedtobemonitored.Ananaloginputvoltagemightbeusedtosetthespeedofinterest.WhichistherightADCarchitecture:a)Forthecurrentmeasurement,whichismeasuredasvoltageacrossashuntresistorb)FortheDClinkvoltagemeasurement,whichisalsoatahigh-voltagepotentialc)Forthetemperatured)Fortheanaloginputvoltage11Training10a)Forthecurrentmeasurement,whichismeasuredasvoltageacrossashuntresistor-Thevoltageacrosstheshuntresistorhastobesmalltokeepthepowerlosssmall-TheinterfaceneedstobegalvanicallyisolatedADCArchitecture:Delta-SigmaModulator-Highresolutionevenatalowinputvoltage-2wireinterface(clock,data)12Training10b)FortheDClinkvoltagemeasurement,whichisalsoatahigh-voltagepotential-8-10bitresolutionisenough-TheinterfacemightrequiregalvanicisolationADCArchitecture:Delta-SigmaModulatororintegratedADCinμ−controllerifusinganisolatedsensor13Training10c)Forthetemperature:-8bitenough-slowspeedADCArchitecture:integratedADCinμ−controller14Training10d)Fortheanaloginputvoltage:-12-16bitaccuracy(noise,INL)-16kSPSconversionrate-+/-10VsignalsADCArchitecture:DeltaSigmaorSARADCAlternativefora-e):multi-channelSARADC15Training10e)Theanglecouldbemeasuredwithanopticalencoder.Ifthemotorrotateswithamaximumof6000rpmandtheencoderhas2000stripes,thenthesinewave,whichneedstobemonitored,reaches200kHz.Signalperiod360ºelect.ϕ1ABPAMANAPBNBMBϕ216Training10e)Fortheanaloginputvoltage:-10-12bitaccuracy(DNL)-Snapshotonexternalholdsignal-Upto500kHzsignalsADCArchitecture:SARADC17Training105.IndustrialweightScaleThescaleshouldbeaccurateto0.5kg,overarangeof0to40tons.WhataretheimportantspecificationsandwhatisthebestADCarchitecture.18Training10WeightScale:-17bit(noise,INL)-SlowspeedADCArchitecture:Delta-SigmaADC19Training106.Touchscreen:TheXandtheYcoordinateshavetobemeasuredofthefingerpositiononascreen.AmultiplexerisusedtoconnecteithertheXortheYcoordinatetooneADCinput.Humanmotionisslow,sothat100kSPSismorethanenough.Theresolutionshouldbehigherthan10bits.WhataretheimportantspecificationsandwhatisthebestADCarchitecture.20Training10TouchScreen:-10-12bit-100kHz-Snapshot,multi-channelADCArchitecture:SARADC21Training107.A/VAmplifiersincludeanADCandaDAC,sothattheaudiosignalcanbedigitizedfirst,thenprocessedwithaDSPandfinallyconvertedbackintotheanalogdomaintodrivetheloudspeakers.WhataretheimportantspecificationsandwhatistherighttypeofADC.22Training10Audio:-20+bit-0-25kHzcontinuoussignals-SignaldelayuncriticalADCArchitecture:Delta-SigmaADC