【doc】一种宽电源电压带隙基准源的设计

【doc】一种宽电源电压带隙基准源的设计 一种宽电源电压带隙基准源的设计 第29卷第8期 2008年8月 半导体 J0URNALOFSEMICONDUCTORS Vo1.29No.8 Aug.,2008 DesignofaBandgapReferencewithaWideSupplyVoltageRange SunYueming,ZhaoMenglian,andWuXiaobo (InstituteofVLSIDesign,ZhejiangUniversity,Hangzhou310027,China) Abstract:Anon— chipvoltagereferencewithawidesupplyvoltagerangeisrequiredbysomeapplications,especiallythat ofpowermanagement(PM)controllerchipsappliedtotelecommunication,automotive,lightingequipment,etc.,when highpowersupplyvoltageisneeded.Accordingly,anewbandgapreferencewithawidesupplyvoltagerangeisproposed? Duetotheimprovedstructure,itfeaturesahighpowersupplyrejectionratio(PSRR)andhightemperaturestability.In addition.allauxiliarymicro— powerreferenceisintroducedtosupportthesleepmodeofthePMchipandreduceitsstandby powerconsumption.Theauxiliaryreferenceprovidesbiascurrentsinnormalmodeanda1.28Vreferencevoltageinsleep modetoreplacethemainreferenceandsavepower.Simulationresultsshowthatthereferenceprovidesareferencevolt— ageof1.27V,whichhasa3.5mVdriftoverthetemperaturerangefrom一20to120? and56/*Vdeviationoverasupply voltagerangefrom3to40V.ThePSRRishigherthan100dBforfrequencybelow10kHz.Thec ircuitwascompletedin 1.5umBCD(Bipolar—CMOS— DMOS)technology.Theexperimentalresultsshowthatallmainexpectationsareachieved. Keywords:widesupplyvoltagerange;bandgapreference;lineregulation;sleepmode;micro power EEACC:2570A CLCnumber:TN433Documentcode:AArticleID:0253—4177(2008)08—1529—06 1Introduction Bandgapreferenceiswidelyappliedinmostana— logandmixedsignalintegratedcircuits(ICs).Since someICs,especiallyPM1Cs,workunderawideoper— atingvoltagerange,typically24V/48Vincommunica? tionapparatus,14V/42Vinautomobiles,and3to40V inlightingsuchasLEDequipment.Thus,abandgap referencecapablcofoperatingwithawidesupply voltagerangeisdemandedinsuchapplications. Asavoltagereference,thebandgapreference shouldprovideavoltageindependentofpowersupply andtemperature.Moreover,highPSRRisalsoacriti. calfeaturesincethepowersupplyrippleswillaffect itsstabilityandinfluenceitsoutputreferencevolt. age. Atypicalbandgapreferencecontainstwovoltage sourceswithoppositetemperaturccocfficients(TC) tocompensatcitstemperaturedrift.ThepositiveTC (PTC)voltagesourceconsistsofatransistorpairwith differentemitterareas.Theirbase.emittervoltage difference(AVBE)isanidealPTCvoltagesource.The voltagewithnegativeTC(NTC)isderivedfromthe forwardvoltagesofpnjunctions.Byaboratively matchingtheoppositeTCsoftwovoltagesources,ac. curatetemperaturecompensationcanbeachieved overacertainrange. Intheconventionaltopology,theoffsetvoltage (Vos)oftheamplifierisamajorerrorsourceandis unpredictablesinceitisarandomerrorproduced fromdispersionduringthemanufacturingprocess4.. Moreover,thisstructurerestrictstheoperatingsupply voltagerangebecausethecommonmodeinputvoltage oftheamplifierislimited.Themarginoftheam. plifieralsorestrictsthePSRR. Inthispaper,anovelbandgapreferencestructure isproposed.Differentfromconventionalstructures, itsPTCvoltageisdirectlygeneratedbyaninneram— plifier.Moreover,theinneramplifierissuppliedbya pre—regulatedreferencevoltage,whichguaranteesits n'ormaloperationoverawidesupplyvoltagerange.It alsoeffectivelyimprovesthePSRRandloadregula— tionofthereference.Thenovelbandgapreference wasimplementedin1.5#mBCD(bipolar.CMOS. DMOS)technologyandverifiedbyexperimentalre. su1ts. 2Proposedbandgapreference Figure1showsaconventionalbandgapreference andFigure2showsthecompleteschematicofthe proposedbandgapreference.Thereferenceisdiffer. entfromconventionalone.Itiscomposedoftwo parts:amicro'powerreferenceandapowersupplyin— dependentbandgapreference.Itcanbeimplantedin. ProjectsupportedbytheNationalNaturalScienceFoundationofChina(No.90707002)andt heNaturalScienceFoundationofZhejiangProvince (No.Z104441) tCorrespondingauthor.Email:zhaoml@zju.edu.cn Received26January2008,revisedmanuscriptreceived29February2008? 2008ChineseInstituteofElectronics 1530半导体第29卷 Fig.1Conventionalbandgapreference toatypicalswitchmodepowersupply(SMPS)con' trollerIC.Inaddition,itsupportstheprevailingsleep' modetechnique.Whenthecontrollerisshutdown, onlythemicro?powerreference1sactive,providinga roughthresholdvoltageforthestartupcomparator- Whilethecontrollerisworking.thesupply?independ? entbandgapreferencewillbeactivatedtoprovidea moreprecisereferencevoltage. 2.1Micro—powerreference Thiscircuithastwocharacteristics:providinga primaryreferencevoltageof1.28VfortheRUN comparatorwhenthecontrollerisinsleepmodeand providingaPTATcurrentforthesupply?independent bandgapreferenceandothercircuitblockswhenthe controllerisworking.Whileworkingastheprimary reference,itstypicalquiescentcurrentislessthan 10t~A,whichmakesitfeaturemicro—powerdissipa— tion.Byusingtransistorsthatcanendurehighvolt— age.itcanbedirectlysuppliedbyVIN,whichmayva- ryfrom3to40V. TheprincipleofthiscircuitisshowninFig.3. Here,mistheratiooftheemitterareasofQA2 andQA1,aisthecurrentgainofM1,M3,andis thecurrentgainofM4,M6.AresistorRlofseveral megaohmsdeterminesthecurrentIA.Theforward voltagesofthebase?emitter(BE)ofQA1andQA2 are: T BE_QAl=TIn(1) Q — I———] l + }—m 1丽?一 }MI,_1_— ..J' 卜 . : q...—_JQQAQB8t__JR} 『lI Micron''crrcllzrence&biascircuitsSuppbindcpcndcmbandgaprcli:rcnce Fig.2Proposedsupply—independentbandgapreference Fig.3Micro—powerreference BE_n) whereV=kT/q,kistheBoltzmann'sconstant,qis theelectroncharge,TisthetemperatureinKelvin (orabsolutetemperature),andIssisthereversesatu' rationcurrentofthebase.emitterjunctionofQA1. UsingthecurrentmirrorM1——M3,thecurrent IM2and1M3is: IM2=IM3=a/A(3) ThenthevoltageacrossR2andR3becomes: VR2=IM2R2=aIAR2(4) VR3=(IM3+IM4)R3=(alA+IB)R3(5) BecauseQA1andQA2sharethesamebasenode, thebasevoltageis: BE_oAl+VR2=VBE_QA2+VR3(6) FromEqs.(1),(5),wecanderive: R3IB+a/A(R3一R2)=VTlnm(7) Here,R2isequaltoR3.Thus,aproportionaltoabso— lutetemperature(PTAT)currentisobtainedas: JB Therefore,theoutput voltagereferenceis: VTInm R voltage (8) ofthemicro?power VREFl=VBE_QA4+IpTlATR5 =+卢(9) whereBE-QA4hasanegativetemperaturecoefficient. Thus,astablereferencevoltagewithanearzerotem? peraturecoefficientcanbeobtainedbychoosingap. propriatevaluesof卢,R3,R5,andm. BecausethebiascurrentIAisgeneratedbyR], thisreferencedoesnotneedastartupcircuit.Moreo. ver.theaccuracyofRisnotcriticalbecausetheref— erencevoltagedoesnotdependuponIA. TransistorsM7andQA3formafeedbackloopto keepQA1andQA2workingintheforwardactivere? gion.IfthesupplyvoltageVINrises,thevoltageacross R2andR3willalsorise,aswellasthegatevoltageof M7.ThenthecurrentflowingthroughM7andQA3 risestoo,pullingupthebasevoltageofQA3,QA1, 第8期 SunYuemingeta1.:DesignofaBandgapReferencewithaWideSupplyVoltageRangel531 Fig.4Proposedsupply—independentbandgapreference andQA2.Asaresult,QA1andQA2keeptheirstatus intheforwardactiveregion.TransistorM6worksasa voltagecontrolledresistor.BecauseR2equalsR3, whensupplyvoltageVINclimbsup,thevoltagevaria— tionovergateandsourcenodesofM6isapproximate— lyequa1.SothecurrentflowingthroughM6isnotin— fluencedbythesupplyvoltage. Inthelayoutofthisbandgapreference.R5isre— placedbyseveraltrimmableresistorstoachieveapre— cisepredictedreferencevoltageaftertape—outing. 2.2SuppLy—independentbandgapreference Usingauniquestructuretogeneratetherefer— eneevoltage,thebandgapreferencehasgoodlinereg— ulation.Differentfromthemicro—powerreference above,itcansupplyacurrentuptolmA,whichissig— nificanttotheSMPScontroller.Inaddition.thisref— ereneecanbeshutdowninsleepmodetosavepower. ThedetailedcircuitisshowninFig.4. Usually,bipolartransistorshaveasmalleroffset andhighergainthanMOStransistors_6].Thus,bipolar transistorsareadoptedasinputdifferentialpairsto reducetheoffsetandtoprovideahighergain. Here,theparameternistheratiooftheemitter junctionsizesofQB3andQB4.Ibi.isabiascurrent providedbythemicro—powerreference.Transistors QB1,QB4andresistorR9constituteanOTAcircuit. Whileworkingstably,thecurrentsflowingthrough QB3,QB4differentia1pairswil1tendtobeequa1. Thus,thedifferenceofthebase.emittervoltageof QB3andQB4is: ?VBE=VBE_oB3一BE_oB4 =一VTlnn(10) ThebasenodesofQB3andQB4clampthevolt— agedropacrossR7,generatingaPTATcurrent Fig.5ReversednestedMillercompensation throughR7.Thereferencevoltageincludestwoparts: thePTCvoltageacrossR6andR7,whichisproduced bythePTATcurrent,andtheNTCvoltageofVBE. REF=脏-oB5+(R6+R7) 1,7 =BE_oB+(R6+R7)(11) 1,7 TransistorsQB6,,QB9constituteafeedbackloop tostabilizethecollectorcurrentofQB5.Ifthiscur— rentfalls,thevoltageacrossR7willbecomesmaller, whichisamplifiedbytheOTA.ThebaseofQB6is connectedtothereverseoutputterminalofOTA: therefore.italsorises.TransistorQB7isbiasedby QB5,soitalwaysworksintheforwardactiveregion. QB6andQB7canberegardedasasimpleamplifier. Therefore,thevoltagerisingofthebaseofQB6cau— sesasignificantreductioninthecollectorcurrentof QB8andthenanincreaseinthebasevoltageofQB9. Asaresult,thecurrentflowingthroughRe,R7,and QB5risesandsucceedsincompensatingtheinitial currentfluctuation.Thus,thecurrentflowingthrough QB5stabilizes. HeretransistorQB9isthekeycomponent.It worksintheforwardactiveregion.Thecurrentflow— ingthroughQB9ensuresthelargecurrentoutputabil— ityofVREFuptolmA.Inaddition,becauseQB9is forwardbiased,thevoltageonnodeAequalstheref— ereneevoltageplusVBE(forward—biaseddiodevoltage dropofQB9).Itisabout2Vinthisdesignandispow— ersupply—independent,ensuringthecircuitcanbesup— pliedbyawidevoltagerange. 2.3Frequencycompensation Asmentionedabove,theamplifierusedtostabi— lizethereferencevoltageisasathree—stageampli— fier,asshowninFig.5,andonlytheinnerstagecon— stitutedbyQB6andQB7hasapositiveG2.Here,the pointsA,B,andCcorrespondtothoseinFig.4.In thissituation,reversednestedMillercompensation (RNMC)isthemostsuitableapproachE.Basedon theMillereffect,thedominantpolePisrelatedto thecompensationcapacitorCc】.Therefore,thevalue ofCc1determinesthesystem'sstability.Here,nulling resistorsareintroducedtocanceltheRHPzeroandto achieveabetterhigh—frequencydynamicrange.More— 1532半导体第29卷 12 1,2 之12 j12 12 12 12 Fig.6Simulatedtemperaturedependenceofoutputreference voltage Powersupply/V Fig.7Simulatedoutputvoltageofbandgapreferencecircuit versuspowersupply over,aproperresistorloadattheoutputnodecanal? soreducetheoutputimpedanceforbetterstability. 3Simulationandexperimentalresults Simulationsoftheproposedbandgapreference werepreformedin1.5ptmBCDtechnology.Figure6 showsthesimulatedoutputvoltagesofthetworefer. ences,micro?powerreference,andsupply?independent reference,respectively,whentemperaturesweeps from一20to120~C.Here,asupplyvoltageof12Vis applied.TheVREF1ofthemicro—powerreferencehasa maximumdriftof?3mVaroundthemeanoutput voltageof1.286V.TheVREFofthesupply?independ. entreferencehasamaximumdriftof?1.7mV aroundthemeanoutputvoltageof1.276V. Figure7showsthesimulatedoutputvoltageof powersupply?independentreferenceasafunctionof thepowersupplyvoltageat27~C.Thefigureshows thatthelineregulationof1.5uv/visachievedover thesupplyvoltagerangefrom3to40Vwithamaxi. mumquiescentcurrentof801.tA. Poweredbya12Vsupply,thesimulatedPSRR curveofthebandgapreferenceisshowninFig.8.The curveshowsthatthePSRRishigherthan100dBfor frequenciesbelow1OkHz. ? ? 凸_ Fig.8SimulatedPSRRofthebandgapvoltagereference Outputcurrent/mA Fig.9Simulatedoutputvoltageofbandgapreferencecircuit versusoutputcurrent Fig.10Photographofproposedbandgapreference Figure9showsthesimulatedoutputvoltageof thebandgapreferenceasafunctionoftheoperating currentwhenpoweredbya12Vsupply.TheVREFis nearlylinearwiththeoperatingcurrentandthemaxi? mumvariationisabout22mV. Thebandgapcircuitwasfabricatedin1.5#m 2p2mBCDtechnology.Thechipphotographisshown inFig.10.Thecircuitareais1180/.tm×434I~minclu? dingtwotrimmingresistorarrays. ThetestingschemesareshowninFig.11. Adjustingthesupplyvoltagefrom2.5to16V,the measuredlineregulationcurveisplottedinFig.12. Thecurveisflatoverawiderangeofinputvoltages from2.5to10Vwithadriftofabout300/~V.Adra? maticchangehappenswhenVINexceeds10V.Thisis duetothetransistorbreakdownunderhighvoltages, whichisrestrictedbytheprocess.Theworkingvolt. agecouldextendto40Viftheproperhighvoltage processisavailable. Testingschemeoflineregulation Testingschemeofloadregulation Fig.11Testingschemesforlineandloadregulation 第8期SunYueminget口 1.:Design.faBandgapReferencewithaWideSupplyVoltageRange1533 Fig.12Measuredoutputvoltageofbandgapreferencecircuit versuspowersupply l28 l26 124 122 120 1.18 116201*30bt401*50g60p80g100tr25(1051111211325m40m 1,oAJA Fig.13Measuredreferencevoltageversusoutputcurrentcurve ofthebandgapreferencecircuit Theloadregulationwastestedatasupplyvoltage of8V.Amicroamperemeterinserieswithaloadre- sisterRLisusedtomonitorthecurrent.Byadjusting |RL,thecurveofVREFversusoutputcurrentisob- tained.asshowninFig.13. Forsupplyvoltagesbetween2.5and10V,the testshowsthatthemaximumquiescentcurrentofthis referenceis66pAinnormalmodeand10.5Ain sleepmode. Table1summarizesthereferencesDecifications obtainedfromsimulationandmeasurement,respec- tively. Table1Simulatedandmeasuredresultsoftheproposed bandgapreference SpecificationSimulatedMeasured Supplyvoltagerange3,40V2.5,10V Supplydependency1.5t~v/v40t~V/V 一 2O,120oC Temperaturecoefficient 20ppm 0,1mA0,100btA Loadregulation 22mV/mA20mV/mA PSRR(<10kHz)102dB MaximumquiescentSleepmode90uW105~W powerconsumptionNormalmode556~W660gW *Limitedbyrecentproeess **Thevalueatsupplyvoltageof10V Table2presentsacomparisonbetweentherefer— enceandreportedwide—rangesuppliedbandgaprefer— encesandshowsthattheproposedreferenceoffers betterlineregulationthanthosepreviouslyreported. Table2Comparisonofwide—rangesuppliedbandgapreference Rincon—MoraEs3Pau1[93Thiswork Year199820052007 2"mCMOS Technologywithanadded0.5um—BCD1.5fxm—BCD P—baselayer Supplyvoltage4 , 8V2.5,10V1.2,10V range—— Measuredline 408uV/V2mV/V40~V/V regulation 4Conclusion Abandgapreferencefeaturingsupply-independ- entperformanceoverawiderangeofsupplyvoltages wasdesignedandfabricatedin1.5ptmBCDtechnolo- gY.Anovelstructurewasproposedtoimproveltsper' formancessuchasPSRRandtemperaturestability. Moreover,anauxiliarymicro-powerreferencewasin- troducedtosupportthesleepmodeandreduceits standbypowerconsumption.Experimentalresults showedthatbesideswidesupplyvoltageadaptability, anearzerotemperaturecoefficientof20ppm/?,a lineregulationof40tzV/V.aPSRRhigherthan 100dB.andaloadregulationof22mV/mAwerealso achjeved. AcknowledgmentsTheprojectreceivedsupportfrom theNationalSemiconductorCorp.(NSC).Thean- thorswouldliketothankDavidPace,KalonChu,and GuyCheung,theseniorengineersofNSC,fortheir helpfuldiscussionsandinstructions. References [1]SodagarAM,NajafiK.Awide—rangesupply—independentCMOS voltagereferencefortelemetry—poweringapplications.Proceed— ingsoftheIEEEInternationalConferenceonElectronics,Cir— cuits,