AD7745中文资料

24-BitCapacitance-to-DigitalConverterwithTemperatureSensorAD7745/AD7746Rev.0InformationfurnishedbyAnalogDevicesisbelievedtobeaccurateandreliable.However,noresponsibilityisassumedbyAnalogDevicesforitsuse,norforanyinfringementsofpatentsorotherrightsofthirdpartiesthatmayresultfromitsuse.Specificationssubjecttochangewithoutnotice.NolicenseisgrantedbyimplicationorotherwiseunderanypatentorpatentrightsofAnalogDevices.Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.OneTechnologyWay,P.O.Box9106,Norwood,MA02062-9106,U.S.A.Tel:[phone]©2005AnalogDevices,Inc.Allrightsreserved.FEATURESCapacitance-to-digitalconverterNewstandardinsinglechipsolutionsInterfacestosingleordifferentialfloatingsensorsResolutiondownto4aF(thatis,upto21ENOB)Accuracy:4fFLinearity:0.01%Common-mode(notchanging)capacitanceupto17pFFull-scale(changing)capacitancerange:±4pFTolerantofparasiticcapacitancetogroundupto60pFUpdaterate:10Hzto90HzSimultaneous50Hzand60Hzrejectionat16HzTemperaturesensoron-chipResolution:0.1°C,accuracy:±2°CVoltageinputchannelInternalclockoscillator2-wireserialinterface(I2C®-compatible)Power2.7Vto5.25Vsingle-supplyoperation0.7mAcurrentconsumptionOperatingtemperature:–40°Cto+125°C16-leadTSSOPpackageAPPLICATIONSAutomotive,industrial,andmedicalsystemsforPressuremeasurementPositionsensingLevelsensingFlowmetersHumiditysensingImpuritydetectionGENERALDESCRIPTIONTheAD7745/AD7746areahighresolution,Σ-Δcapacitance-to-digitalconverter(CDC).Thecapacitancetobemeasuredisconnecteddirectlytothedeviceinputs.Thearchitecturefea-turesinherenthighresolution(24-bitnomissingcodes,upto21-biteffectiveresolution),highlinearity(±0.01%),andhighaccuracy(±4fFfactorycalibrated).TheAD7745/AD7746capacitanceinputrangeis±4pF(changing),whileitcanacceptupto17pFcommon-modecapacitance(notchanging),whichcanbebalancedbyaprogrammableon-chip,digital-to-capacitanceconverter(CAPDAC).TheAD7745hasonecapacitanceinputchannel,whiletheAD7746hastwochannels.Eachchannelcanbeconfiguredassingle-endedordifferential.TheAD7745/AD7746aredesignedforfloatingcapacitivesensors.Forcapacitivesensorswithoneplateconnectedtoground,theAD7747isrecommended.Thepartshaveanon-chiptemperaturesensorwitharesolutionof0.1°Candaccuracyof±2°C.Theon-chipvoltagereferenceandtheon-chipclockgeneratoreliminatetheneedforanyexternalcomponentsincapacitivesensorapplications.Thepartshaveastandardvoltageinput,whichtogetherwiththedifferentialreferenceinputallowseasyinterfacetoanexternaltemperaturesensor,suchasanRTD,thermistor,ordiode.TheAD7745/AD7746havea2-wire,I2C-compatibleserialinterface.Bothpartscanoperatewithasinglepowersupplyfrom2.7Vto5.25V.Theyarespecifiedovertheautomotivetemperaturerangeof–40°Cto+125°Candarehousedina16-leadTSSOPpackage.FUNCTIONALBLOCKDIAGRAMSDIGITALFILTER24-BITΣ-∆MODULATORCLOCKGENERATORMUXTEMPSENSORCAPDACCAPDACVOLTAGEREFERENCECONTROLLOGICCALIBRATIONAD7745VDDREFIN(+)REFIN(–)GNDSDASCLRDYVIN(+)VIN(–)CIN1(+)CIN1(–)EXCAEXCB05468-001I2CSERIALINTERFACEEXCITATIONFigure1.DIGITALFILTER24-BITΣ-∆MODULATORMUXTEMPSENSORCAPDACCAPDACVOLTAGEREFERENCECONTROLLOGICCALIBRATIONAD7746VDDREFIN(+)REFIN(–)GNDSDASCLRDYVIN(+)VIN(–)CIN1(+)CIN1(–)CIN2(+)CIN2(–)EXC1EXC205468-002CLOCKGENERATORI2CSERIALINTERFACEEXCITATIONFigure2.AD7745/AD7746Rev.0|Page2of28TABLEOFCONTENTSSpecifications.....................................................................................3TimingSpecifications.......................................................................5AbsoluteMaximumRatings............................................................6PinConfigurationsandFunctionDescriptions...........................7TypicalPerformanceCharacteristics.............................................8OutputNoiseandResolutionSpecifications..............................11SerialInterface................................................................................12ReadOperation...........................................................................12WriteOperation..........................................................................12AD7745/AD7746Reset.............................................................13GeneralCall.................................................................................13RegisterDescriptions.....................................................................14StatusRegister.............................................................................15CapDataRegister.......................................................................15VTDataRegister........................................................................15CapSet-UpRegister...................................................................16VTSet-UpRegister....................................................................16EXCSet-UpRegister..................................................................17ConfigurationRegister..............................................................18CapDACARegister...................................................................19CapDACBRegi