TIREPRESSUREMONITORINGSENSOROPTIMIZEDFOR250kPa 450kPaGENERALDESCRIPTIONTheMotorolaMPXY8020Aisan8 pintiremonitoringsensorwhichiscomprisedofavariablecapacitancepressuresensingelement,atemperaturesensingelement,andaninterfacecircuit(withawake upfeature)allonasinglechip.ItishousedinaSuper SmallOutlinePackage(SSOP),whichincludesamediaprotectionfilter.Specificallydesignedforthelowpowerconsumptionrequirementsoftirepressuremonitoringsystems,itcancombinewithaMotorolaremotekeylessentry(RKE)systemtofacilitatealow costhighlyintegratedsystem.DetailedDescriptionTheblockdiagramoftheMPXY8020AisshowninFigure1.Thepressuresensorisacapacitivetransducerconstructedusingsurfacemicromachining,thetemperaturesensorisconstructedusingadiffusedresistor,andtheinterfacecircuitisintegratedontothesamedieasthesensorsusingastandardsiliconCMOSprocess.Theconditioningofthepressuresignalbeginswithacapacitancetovoltageconversion(CtoV)followedbyaswitchedcapacitoramplifier.Thisamplifierhasadjustableoffsetandgaintrimming.Theoffsetandgainarefactorycalibrated,withcalibrationvaluesstoredintheEEPROMtrimregister.Thisamplifieralsohastemperaturecompensationcircuitsforbothsensitivityandoffset,whichalsoarefactory adjustedusingtheEEPROMtrimregister.Thepressureismonitoredbyavoltagecomparator,whichcomparesthemeasuredvalueagainstan8 bitthresholdadjustedbyaserialinput.ByadjustingthethresholdandmonitoringthestateoftheOUTpintheexternaldevicecancheckwhetheralow pressurethresholdhasbeencrossed,orperformupto8 bitA/Dconversions.Thetemperatureismeasuredbyadiffusedresistorwithapositivetemperaturecoefficientdrivenbyacurrentsource,therebycreatingavoltage.Theroomtemperaturevalueofthisvoltageisfactory calibratedusingtheEEPROMtrimregister.Atwo channelmultiplexercanrouteeitherthepressureortemperaturesignaltoasamplingcapacitorthatismonitoredbyavoltagecomparatorwithvariablethresholdadjust,providingadigitaloutputfortemperature.Aninternallowfrequency,lowpower5.4kHzoscillatorwitha14 stagedividerprovidesaperiodicpulsetotheOUTpin(divideby16384for3seconds).ThispulsecanbeusedtowakeupanexternalMCUtobeginaninterfacewiththedevice.Anadditional10 stagedividerwillprovideapulseevery52minuteswhichcanbeusedtoresetanexternalMCU.Thepowerconsumptioncanbecontrolledbyseveraloperationalmodesselectedbyexternalpins.本公司庫存量大，為減小庫存，現(xiàn)特價處理