第3章-参考电平

1SENANJINGwujinCMOSAnalogICDesignCMOSAnalogICDesignChapter3Chapter3BandgapBandgapVoltage&CurrentReferenceVoltage&[e-mail]@seu.edu.cnVersionVersion--II,2012,09II,2012,092SENANJINGwujinConstantConstant••PrincipleofPrincipleofBandgapBandgapVoltageReference(BGR)VoltageReference(BGR)••PTAT&CTATPTAT&CTAT••Linear&nonlinearcompensatedBGRLinear&nonlinearcompensatedBGR••VoltageMode&CurrentModeBGRVoltageMode&CurrentModeBGR••CurrentReferenceCurrentReference3SENANJINGwujinWhatisReferenceWhatisReferenceThecurrentorthevoltagethatisindependentwithtemperatureandsupplyvoltage,andalsoinsensitivitywiththefabricationprocess,iscalledasvoltageorcurrentreference,usuallyknownasPVTstabilityPVTstability..Howabouttheoutputcurrentsandthegatevoltagesoftheself-biasedcircuit?Bothcurrentandgatevoltageofself-biasedcircuit,theyareallnearlyindependentwithsupplyvoltage,butallaresensitivewithtemperature,eitherforV/RorΔV/Rtype.4SENANJINGwujinHowtogetareferenceHowtogetareferenceTCTC:TemperatureCoefficient(ppm/°C)PTAT:Proportiontoabsolutetemperature(PositiveTC)CPTAT:ContraryPTAT(NegativeTC)V-I/I-V:Voltage(current)tocurrent(voltage)converter;;VM/CM:Currentmode/VoltageMode;Curvaturecompensation:firstorderlinearandhighordernonlinearcompensation.IsthereanyreadyIsthereanyready--madereference?Nomadereference?No！！Method:TemperatureCompensationPrinciple;Method:TemperatureCompensationPrinciple;SelfSelf--biasedarchitectures.biasedarchitectures.ZeroTC=ZeroTC=λλPP××PTAT(fixedPPTAT(fixedP--TC)+TC)+λλNN××CPTAT(fixedNCPTAT(fixedN--TC)TC)5SENANJINGwujinTheoryofReferenceTheoryofReferenceTemperatureCompensationPrinciple(1thorderlinear,highordernonlinear)ConstantTCofpositivevoltage(PTAT)&negativevoltage(CTAT)VoltageMode&CurrentModeVoltageReference(BGR)Outputvoltage&loaddrivingcapabilityBiasing,startup,PSRRandoffsetofBGRCurrentreferenceanditsrelationwithBGR6SENANJINGwujinTemperatureCompensationPrincipleTemperatureCompensationPrincipleSimple：LinearcompensationBothP-TC&N-TCofVoltage/currentshouldbekeepconstantduringawidetemperaturerangeForsmallP-TC(lessthanN-TCinquantity),itshouldbeextendedmtimestocompensatethatofN-TC.Method:V-I-VconverterforvoltagesummingandP-TCprocessing.VMBGR:VVrefref==VVBEBE+kV+kVTT,k≈23CMBGR:VVrefref=R=R33(V(VBEBE/R/R11+m+m11VVTT/R/R22)=)=m(Vm(VBEBE+kV+kVTT),),m=R3/R1,k=m1R1/R2Curvaturecompensation：HighordercompensationtodealwiththenonlinearinN-TCandP-TC.7SENANJINGwujinCPTATCPTATNN--TC:TC:VVBEBE,nearlyconstant,somenonlinearexisted,nearlyconstant,somenonlinearexistedVBE0≈600mV@(T0=300k),currentbiasingrelated0000()()()()lnBEGBEGTTTVTVTVVVTTηα=+−−−CmVTTVTTVVTVTGBEBE°−≈+−−−=∂∂/2)1(ln000αηNLlocatedLinearN-TCNLTCVariedwithprocess,currentlevel,temp.8SENANJINGwujinPTATPTATIndirectwaytoobtainPTATbyΔVBEorΔVGSwhichoperatedinW.I.range,Iin/Iout=1,Se2/Se1=N00ln(ln)(ln)TBETVkVVNNTNTqTΔ===ThedistanceofTCbetweenVBEandVTisnearlyaconstant/2/23/0.087/BETVTmVCkVTmVC∂∂°=≈≈∂∂°0026TkTVmVq=≈000.087/TTVVmVCTT∂=≈+∂o@T0=300k9SENANJINGwujinVVrefrefoutputforVMBGRoutputforVMBGR110000(ln)()BErefBEBETBETVRVVMRVMNVVTkVRRΔ=+×=+≈+0()60023261.2refVTmVmVV≈+×≈TheVrefisfixedaround1.2VforVMBGRifthecircuitcanproperlyoperatedundertheminimalVDDofover1.2V.WhyVrefisnearlyunrelatedwithVDDwhentheBGRcanoperate;WhyVrefisnearlyunrelatedwithTemp.?TC≡0?;IsVrefnealyunrelatedwithfabricationProcess?TrimmingHowtoobtainavoltagereferenceofless1.2VorwhenVCC1.2V?IflineartransferratioisM,then10SENANJINGwujinWhereBGRcomefrom?WhereBGRcomefrom?()()refbeTVTVTmV=+⋅0refbedVdVkmdTdTq=+=00000000()[1ln]0beGTTVVVVTmTTTTαη−+−++=0()()(1ln)refGTTVVTVTηα≈+−−004,()()(/)nnTTTTημμ−=−=m≈23TTVmmVTT)(00=212()(0)()GGVTVTCTTCT≈+Δ+Δ000()(/),1,biasbiasRRRIITTTTCTαααα==−=⋅}2,0,21≤≤ααRn0ηα−开口向下0)()(00≈≈TTCTVVrefGref，11SENANJINGwujinCurrentModeCurrentMode--BGRPrincipleBGRPrinciple__1,outrefCMrefVMRVVRκκ==0110110()(ln)(ln)BEToutoutoutBETVVIIRRNRRRRVNVRR+=+=+Bycurrentmode,VBEispartialscaledandderivedtotheoutputbycurrenttransportation,arbitraryVref_CMisobtainedbyvariableκ.VoltageModeBETBEBEVVNRRVRIRVI+⇒+⇒Δ=)ln(211100CurrentMode0011BEBEVIRVIRΔ==}⇒RelationofVM&CMVÆIÆVprinciple12SENANJINGwujinHighHigh--ordercompensatedPrincipleordercompensatedPrincipleResidualnonlinearTCcanonlybecompensatedby--segmentalcompensation(linear/nonlinear);--nonlinearcompensation(oppositeofnonlinearcomponentsareextractedandturnbackforcompensation.--byusingoffsetvoltageartificiallyforcompensation.TCcanbeobviouslyreducedduetomulti-valleyformedinhighorderBGR,buttheriskofpropertydegradationisrelativehigh.13SENANJINGwujinComparisonbetweenVM&CMBGRComparisonbetweenVM&CMBGRComparisonConditionsforcomprisable-SameoutputVref;-Sameoutputcurrentandoutputbranchstructureandparameters(suchasCascode);Conclusion-underconditionsabove,thePSRRofVMBGRisfarlargethanthatofVMVGR;biasTmbeIVgr==1,BEonRVBEbiasVrI−=⇔onBETVV,beRVBErr−WhendiodeisinsteadbyRinCM-BGR,theimpedancefromoutputtoGNDisobviouslyincreased,thusPSRRisdegenerated.14SENANJINGwujinOffsetVoltageEffectOffsetVoltageEffectInpracticecircuits,manyfactorcanbringVosinΔVBE101100__[(ln)]EBOSrefBEBETOSr