ApplicationReportSPRAAD8A–March2007TMS320280xandTMS3202801xADCCalibrationMatthewPate..................................................................................................................AECC2000ABSTRACTThisapplicationreportdescribesamethodforimprovingtheabsoluteaccuracyofthe12-bitADCfoundontheTMS320280xandTMS3202801xdevices.InherentgainandoffseterrorsaffecttheabsoluteaccuracyoftheADC.ThemethodsdescribedinthisreportcanimprovetheabsoluteaccuracyoftheADCtolevelsbetterthan0.5%.ThisapplicationreporthasanoptiontodownloadanexampleprogramthatexecutesfromRAMontheF2808EzDSP.Seethefollowinglinkforthedownload:http://www-s.ti.com/sc/techlit/spraad8.zip.Note:ThedatainthisapplicationreportisbasedonobservationsofADCbehavioronTMS320280xRev-BTMSdevices.Contents1Introduction..........................................................................................22GainandOffsetErrorDefinition..................................................................23GainandOffsetErrorImpact.....................................................................44Calibration...........................................................................................65HardwareConnectivity.............................................................................86ADCSamplingTechniques......................................................................117ExampleSoftwareCalibrationDriver...........................................................158GainandOffsetTemperatureDrift..............................................................179UsefulTips.........................................................................................18ListofFigures1GainandOffsetDefinition.........................................................................32SimplifiedCircuitforIdealADCCase............................................................53ModifiedCircuittoScaleInputtoSafeRangeofADC........................................54ADCActualGain................................................
