ST_Mosfet training

G.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaPowerMOSFETTechnicalTrainingDatasheetOverviewGiovanniPriviteraSeniorProductEngineerMOSFET&[e-mail]rMOSFETDivisionalProductengineeringCataniaMaximumRatingsRepresenttheextremecapabilityofthedevices.Tobeusedasworstconditions(singleparameter)thatthedesignshouldguaranteewillnotbeexceeded.[onlyVDS&VDGRmaybeexceededinlimitedavalancheconditions]Neverexceed!!!!!!!!!!!!G.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaTheavalanchebreakdownvoltageofST’sPowerMOSFETisalwayshigherthanitsvoltageratingduetonormalproductionprocessmargins.Inordertoachievehighforecastedreliabilitytheworstcaseoperatingvoltageshouldbelowerthanthemaximumone.Themaximumvoltageduringturnoffshouldnotexceed70to90%oftheratedvoltage.Thisderatingissuggestedbytheyearsofexperience.FortheDrain-GateVoltagecapability(Rgstoavoidfloatinggate)G.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaExceedingVgsmayresultinpermanentdevicedegradationduetooxidebreakdownanddielectricrupture.Therealoxidebreakdowncapabilityishigherthanthisvalue,andisrelatedtotheoxidethickness;butthisvalue,withareasonableguardband,isthe100%TESTED&warrantedoneG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaTjmustbealwayslowerthan150ºCReflectsaminimumdeviceservicelifetime.OperationatconditionsthatguaranteeajunctiontemperaturelessthanTjmaxmayenhancelongtermoperatinglife.Ptot=dT/Rthjc=(150-25)/Rthjcderating=1/RthjcThemajorityofreliabilitytestsaredoneatmaximumjunctiontemperature,especiallytheHTRB(HighTemperatureReversedBias)andHTFB(HighTemperatureForwardBias).Thesetestresultsareusedasinputinformationforcalculationofaccelerationfactorsindifferentreliabilitymodels.Inordertoachievehighforecastedreliabilitythemaximumoperatingtemperatureshouldbelowerthanthemaximumone.Forexample,bytheoreticalmodels,reducingthejunctiontemperatureby30°CwillimprovetheMTBF(MeanTimeBetweenFailure)oftheMOSFETbyanorderofmagnitude.G.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaPtot=Ron(@Tjmax)*I²Ptot=(Tjmax-Tc)/RTHj-cI=(Tjmax-Tc)/Ron(@Tjmax)/RthjcLimitedalsobywiresize:toavoidanyfuseeffectLimitedbyPtot&RdsonG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaMaximumdv/dtcapabilityduringdiodereverserecovery(dynamicdv/dt)Tobedistinguishedtwokindofdv/dt(staticanddynamic)G.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaIftheparasiticbipolartransistoristurnedon,thebreakdownvoltageofthedeviceisreducedfromBVCBOtoBVCEOwhichis50~60[%]ofBVCBO.IftheapplieddrainvoltageislargerthanBVCEO,thedevicewillbebroughtintotheavalanchebreakdown,andifthedraincurrentcannotbelimitedexternally,thedevicecouldbedestroyedbythesecondbreakdownofparasiticbipolar.Duetothefalseturn-on,thedevicefallsintothecurrentconductionstate,andinseverecases,highpowerdissipationdevelopsinthedeviceandcreatesdestructivefailure.Staticdv/dta)Falseturnonb)ParasitictransistorturnonG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaThevalueofdi/dtanddv/dtbecomeslargerasRgisreduced.Dioderecoverydv/dtThedeviceisdestroyedbythesimultaneousstressessuchashighdraincurrent,highdrainsourcevoltageandthedisplacementcurrentoftheparasiticcapacitance.HighestStresspointG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaSTinsulatedpackagesaretested100%toguaranteethisvalue.G.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaThermalresistanceParameterwhichindicateshoweasilytheheatflowsbetweentwopointsAandBSmallRTHimpliesthattheheatistransferredfromAtoBwithlittletemperaturedifferencebetweenAandBLargeRTHimpliesthatthetransferofthesamequantityofheatfromAtoBrequiresagreatertemperaturedifferencebetweenthetwopointsThermalresistanceisdefinedas:RTHb-a=(Tb-Ta)/PdissG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaThermalresistanceInelectronicdevicesthetwomostimportanttemperaturesaretheambienttemperatureTaandthetemperaturereachedbythejunctionTjTheRTHj-a(device)dependsbyframedimensionandframematerial.TheRTHj-a(module)dependsbythedevice,insulation,mountingmethod,heatsinksizeandcoolingmethod(forcedair,radiation....)G.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaThermalchainexistsfromthesilicontotheambientthroughthedieattach,theframe,thecontactandtheexternaldissipator.RTHj-a=RTHj-c+RTHc-s+RTHs-aThermalmodelfortransienttakesintoaccountthermalcapacitancesThermalresistanceG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaRthjc=1/0.32=3.1K/WV=Ron(@Tj)*IK=0.1Zth=kRthVI=(Tj-Tc)/ZthK=0.04K=0.01K=1AllowedbutnotreachableregionG.PriviteraHighVoltagePowerMOSFETDivisionalProductengineeringCataniaIar,definedasthemaximumcurrentthatcanflowthroughthedeviceduringtheavalancheoperationswithoutanybipolarlatchingphenomenon.EAS(EnergyduringAvalancheforSinglePulse)isdefinedasthemaximumenergythatcanbedissipatedinthedeviceduringasingleav