组件fastreport2.5

TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015TPS2477x2.
5至至18V高高性性能能热热插插拔拔1特特性性3说说明明12.
5V至18V总线操作(30V绝对最大值)TPS2477x是一款针对2.
5V至18V系统的高性能模拟热插拔控制器.
TPS2477x精确且具有高度可编程可编程保护设置:保护设置,对设计故障隔离要求较高的高功率、高可用–电流限制:10mV时为±5%性系统很有帮助.
–快速跳变:20mV时为±10%可编程场效应管(FET)安全运行区域(SOA)保护该控制器还具有可编程电流限制、快速关断和故障定时可编程快速跳变的响应时间器功能,可在热短路等故障期间保护负载和电源.
可双定时器(浪涌/故障)调整快速关断阈值和响应时间,以确保快速响应实际故模拟电流监视器(25mV时为1%)障,同时避免误跳变.
该器件具有可编程的安全工作可编程欠压(UV)与过压(OV)区域(SOA)保护和浪涌定时器,可在所有条件下对金故障和电源正常状态标志属氧化物半导体场效应晶体管(MOSFET)加以保护.
4mm*4mm24引脚四方扁平无引线(QFN)封装TPS2477x将电源正常状态标志置为有效后,会在过流70=锁存,71=重试,72=快速锁存关闭事件期间作为断路器工作并运行故障定时器,但不会限制电流.
当故障定时器到期后,控制器会关断.
该控2应应用用制器具有两个独立定时器(浪涌/故障),用户可根据企业级存储系统需求定制保护功能.
企业级服务器最后,TPS2477x非常灵活,可帮助热插拔设计满足网络卡240VA要求,本数据表中给出了一个设计示例.
240VA应用器器件件信信息息(1)器器件件型型号号封封装装封封装装尺尺寸寸((标标称称值值))TPS24770TPS24771RGE(24)4.
00mmx4.
00mmTPS24772(1)要了解所有可用封装,请见数据表末尾的可订购产品附录.
4简简化化电电路路原原理理图图将将输输出出功功率率限限制制在在240VA,,20AILIM与与TPS2477x实实现现的的对对比比1AnIMPORTANTNOTICEattheendofthisdatasheetaddressesavailability,warranty,changes,useinsafety-criticalapplications,intellectualpropertymattersandotherimportantdisclaimers.
PRODUCTIONDATA.
EnglishDataSheet:SLVSCZ3TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn目目录录9.
1Overview101特特性性.
19.
2FunctionalBlockDiagram102应应用用.
19.
3FeatureDescription.
113说说明明.
19.
4DeviceFunctionalModes.
164简简化化电电路路原原理理图图.
110ApplicationandImplementation.
175修修订订历历史史记记录录210.
1ApplicationInformation.
176DeviceComparisonTable.
310.
2TypicalApplication177PinConfigurationandFunctions.
311PowerSupplyRecommendations408Specifications.
412Layout.
408.
1AbsoluteMaximumRatings412.
1LayoutGuidelines408.
2ESDRatings412.
2LayoutExample428.
3RecommendedOperatingConditions.
513器器件件和和文文档档支支持持438.
4ThermalInformation513.
1相关链接.
438.
5ElectricalCharacteristics.
513.
2商标.
438.
6TimingRequirements713.
3静电放电警告.
438.
7TypicalCharacteristics.
813.
4术语表439DetailedDescription1014机机械械、、封封装装和和可可订订购购信信息息.
435修修订订历历史史记记录录日日期期修修订订版版本本注注释释2015年3月*最初发布.
2Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH20156DeviceComparisonTablePARTNUMBER(1)LATCH/RETRYOPTIONTPS24770LatchTPS24771Auto–RetryTPS24772FastLatchOff(1)Forthemostcurrentpackageandorderinginformation,seethePackageOptionAddendumattheendofthisdocument,orseetheTIwebsiteatwww.
ti.
com.
7PinConfigurationandFunctionsQFN24-PinwithThermalPadRGEPackageTopViewPinFunctionsPINTYPE(1)DESCRIPTIONNAMENO.
ENHS2IActive-highenableinputofHotSwap.
Logicinput.
Connectstoresistordivider.
FLTb4OActive-low,open-drainoutputindicatingvariousfaults.
FSTP16IFasttripprogrammingsetpinforHotSwap.
AresistorisconnectedfrompositiveterminalofRSNStoFSTP.
GND10–Ground.
HGATE18OGatedriveroutputforexternalHotSwapMOSFET.
IMON12I/OAnalogmonitorandcurrentlimitprogrampoint.
ConnectRIMONtoground.
IMONBUF13OVoltageoutputproportionaltotheloadcurrent(0V–3.
0V).
NC1,3,6,NCNoconnect.
Tietogroundorleavefloating.
20–24(1)I=Input;O=Output;P=Power,NC=NoConnectCopyright2015,TexasInstrumentsIncorporated3TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cnPinFunctions(continued)PINTYPE(1)DESCRIPTIONNAMENO.
OUTH19IOutputvoltagesensorformonitoringHotSwapMOSFET'spower.
ConnectstothesourceterminaloftheHotSwapNchannelMOSFET.
OV9IOvervoltagecomparatorinput.
Connectstoresistordivider.
HGATEispulledlowwhenOVexceedsthethreshold.
Connecttogroundwhennotused.
PGHS5OActive-high,open-drainpower-goodindicator.
PLIM11IPowerlimitprogrammingpin.
AresistorfromthispintoGNDsetsthemaximumpowerdissipationfortheHotSwapFET.
Connecta4.
99kΩresistortodisablepowerlimit.
SENM17ICurrent-sensinginputforthesenseresistor.
Directlyconnectstothenegativeterminalofthesenseresistor.
SET15ICurrent-limitprogrammingsetpinforHotSwap.
Aresistorisconnectedfrompositiveterminalofthesensingresistor.
TFLT8I/OFaulttimer,whichrunswhenthedeviceisinregularoperationandthereisanovercurrentcondition.
TINR7I/OInrushtimer,whichrunsduringtheinrushoperation(start-up)ifthepartisincurrentlimitorpowerlimit.
VDD14PPowerSupply8Specifications8.
1AbsoluteMaximumRatingsoveroperatingfree-airtemperaturerange(unlessotherwisenoted)(1)MINMAXUNITVDD,SET,FSTP,SENM,OUTH,ENHS,FLTb,PGHS,OV–0.
330VHGATEtoOUTH–0.
315VSETtoVDD–0.
30.
3VInputVoltageSENM,FSTPtoVDD–0.
60.
3VTINR,TFLT,PLIM,IMON–0.
33.
6VIMONBUF–0.
37VSinkCurrentFLTb,PGHS5mASourceCurrentIMON,IMONBUF5mAStoragetemperature,Tstg–65150°C(1)StressesbeyondthoselistedunderAbsoluteMaximumRatingsmaycausepermanentdamagetothedevice.
Thesearestressratingsonly,whichdonotimplyfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderRecommendedOperatingConditions.
Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.
8.
2ESDRatingsVALUEUNITHuman-bodymodel(HBM),perANSI/ESDA/JEDECJS-001(2)±1500ElectrostaticV(ESD)(1)VdischargeCharged-devicemodel(CDM),perJEDECspecificationJESD22-C101(3)±500(1)Electrostaticdischarge(ESD)measuresdevicesensitivityandimmunitytodamagecausedbyassemblylineelectrostaticdischargesintothedevice.
(2)JEDECdocumentJEP155statesthat500-VHBMallowssafemanufacturingwithastandardESDcontrolprocess.
(3)JEDECdocumentJEP157statesthat250-VCDMallowssafemanufacturingwithastandardESDcontrolprocess.
4Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH20158.
3RecommendedOperatingConditionsoveroperatingfree-airtemperaturerange(unlessotherwisenoted)MINMAXUNITVDD,SENM,SET,FSTP2.
518InputvoltageVENHS,FLTb,PGHS,OUTH018SinkcurrentFLTb,PGHS02mASourcecurrentIMON01mAPLIM4.
99500kΩIMON16kΩExternalresistanceFSTP104000ΩSET10400Ωw/oRSTBL1070RIMON/RSETWithappropriateRSTBL(1)310withCHGATE>47nF(2)10200TINR,TFLT1nFHGATE,(2)01FExternalcapacitorIMON30pFIMONBUF100pFOperatingjunctiontemperature,TJ–40125°C(1)RefertoRSTBLRequirmentforRIMON/RSET101mV)HotSwaptimertimesout.
OverTemperatureShutDown(OTSD)Copyright2015,TexasInstrumentsIncorporated15TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn9.
4DeviceFunctionalModes9.
4.
1HotSwapFunctionalModesThestatemachinefortheHotSwapsectionisshowninFigure17.
AfteraPOR/UVLOeventtheHotSwapenterstheInrushup.
OnceoperationaltheHotSwaphasthefollowingfunctionalmodes:InrushMode(INR):InthisstatetheHotSwapcontrollerisactivelyregulatingtheHGATEtomeetthecurrentlimitandpowerlimitsettings.
Theinrushtimerisrunningifthecontrollerisinpowerorcurrentlimiting.
Iftheinrushtimertimesoutthegatewillbepulleddown.
TheTPS24770andTPS24772willgotolatchedmodeandTPS24771willgointoretrymode.
RegularOperationMode(REG):InthismodeeverythingisoperatingproperlysoboththetimersaredischargedandtheHGATEishigh.
Ifthereisanovercurrentcondition(VSNS>VSNS,CL),thedevicewillgointofaultmode.
Ifthereisafasttripcondition(VSNS>VFSTP),thegatewillbepulleddownwitha1A/63spulse.
TheTPS24772willgotothelatchedstateandtheTPS24770andTPS24771willgobacktoinrushforaretry.
FaultMode(FLT):InthismodetheTPS2477xrunsthefaulttimer.
OncethetimerexpirestheTPS24770andTPS24772willgotolatchmodewhileTPS24771willgotoretrymode.
Iftheovercurrentconditionisremovedthecontrollerwillgobacktotheregularoperationmode.
LatchedMode(Latched):InthelatchedmodetheHGATEislow,thetimerisbeingdischarged,andtheFLTbisasserted.
IfthereisarisingedgeonENHSthepartwilldischargethetimersandgototheinrushmode.
RetryMode(Retry):Herethepartwillchargeanddischargetheinrushtimer64timesbeforeattemptinganotherretry.
Figure17.
HotSwapStateMachine16Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH201510ApplicationandImplementationNOTEInformationinthefollowingapplicationssectionsisnotpartoftheTIcomponentspecification,andTIdoesnotwarrantitsaccuracyorcompleteness.
TI'scustomersareresponsiblefordeterminingsuitabilityofcomponentsfortheirpurposes.
Customersshouldvalidateandtesttheirdesignimplementationtoconfirmsystemfunctionality.
10.
1ApplicationInformationTheTPS2477xisahighlyconfigurableHotSwapcontrollerthatcanbefine-tunedfortheapplicationrequirement.
WhendesigningaHotSwap3keyscenariosshouldbeconsidered:Start-up.
OutputofaHotSwapisshortedtogroundwhentheHotSwapison.
Thisisoftenreferredtoasa"Hot-Short".
Poweringupaboardwhentheoutputandgroundareshorted.
Thisisusuallycalleda"startintoshort".
AllofthesescenariosplacealotofstressontheHotSwapMOSFETandspecialcaremustbetakenwhendesigningtheHotSwapcircuittokeeptheMOSFETwithinitsSafeOperatingArea(SOA).
Notethatthecomponentselectioncanoftenbeiterativelyandit'srecommendedtousethepublicallyavailableexcelcalculatorstocrunchthenumbers.
SeetheTPS24770DesignCalculatorintheTools&SoftwarelinkontheProductfolder.
10.
2TypicalApplicationThreeapplicationexamplesareprovided.
Thefirstoneisfora100AHotSwapwith5,500Fofoutputcapacitancethatusesstandardpowerlimitedbasedstart-up.
Thentherearetwoexamplesofdesigningforthe240VAdesignrequirment.
OneusestheCSD16415Q5B,whichisanoldergenerationMOFSETwithgreatSOA.
ThesecondoneusestheCSD17573Q5B,whichhaslowerSOA,butismorecosteffective(pricevsRDSON).
10.
2.
112V,100A,5,500FAnalogHotSwapDesignThediagrambelowshowstheapplicationschematicforthisdesignexample.
Figure18.
ApplicationSchematicfor100AHotSwapCopyright2015,TexasInstrumentsIncorporated17TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cnTypicalApplication(continued)10.
2.
2DesignRequirementsTable1summarizesthedesignparametersthatmustbeknownbeforedesigningaHotSwapcircuit.
WhenchargingtheoutputcapacitorthroughtheHotSwapMOSFET,theFET'stotalenergydissipationequalsthetotalenergystoredintheoutputcapacitor(1/2CV2).
ThusboththeinputvoltageandoutputcapacitancewilldeterminethestressexperiencedbytheMOSFET.
Themaximumloadcurrentwilldrivethecurrentlimitandsenseresistorselection.
Inaddition,themaximumloadcurrent,maximumambienttemperature,andthethermalpropertiesofthePCB(RθCA)willdrivetheselectionoftheMOSFETRDSONandthenumberofMOSFETsused.
RθCAisastrongfunctionofthelayoutandtheamountofcopperthatisconnectedtothedrainoftheMOSFET.
AircoolingwillalsoreduceRθCA.
It'salsoimportanttoknowifthereareanytransientloadrequirements.
Finally,whethercurrentmonitoringisneededanditsaccuracyrequirementwilldrivetheselectionofRSNS,RIMON,andRSET.
Table1.
DesignRequirementsfora12V,100A,5500FHotSwapDesignDESIGNPARAMETEREXAMPLEVALUEInputvoltagerange11V–13VMaximumDCloadcurrent100AMaximumOutputCapacitanceoftheHotSwap5500FMaximumAmbientTemperature55°CMOSFETRθCA(functionoflayout)50°C/WTransientloadrequirement130Afor250msPass"Hot-Short"onOutputYesPassa"Startintoshort"YesIstheloadoffuntilPGassertedYesCanaHotBoardbepluggedinorPowerCycledNoICusedTPS24772AnalogCurrentMonitorUsedNo10.
2.
3DetailedDesignProcedure10.
2.
3.
1SelectRSNSandVSNS,CLSettingTPS2477xhasaprogrammableVSNS,CLwitharecommendedrangeof10mVto67.
5mV.
ItcanbeusedwithaVSNS,CLupto200mV,butthatrequiresaresistorbetweenSETandSENMtoensurestabilityofaninternalloop.
ThisisshowninFigure19.
RSTBLcanbecomputedusingtheequationbelow.
(10)ForhighpowerapplicationsalowerVSNS,CLleadstobetterefficiencyso20mVistargetedforthisdesign.
Targetingacurrentlimitof110Atoallowmarginfortheload,thesenseresistorcanbecalculatedasfollows:(11)Since0.
18mresistorsaren'tavailable,thecloseststandardresistorshouldbechosen.
Tohavebetterefficiency,three0.
5mresistorsareusedinparallel.
NexttheVSNS,CLshouldbecomputedbasedontheactualRSNSandthenusedtocomputeRSETandRIMON.
RSETischosentotarget250AofcurrentthroughSETandIMONpinsduringcurrentlimit.
(12)(13)ChoseRSETtoequal73.
2,whichistheclosestavailablestandardresistor.
NextobtainthecalculatedRIMON(RIMON,CLC)asfollows:(14)18Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH2015Choose2.
67kresistorforRIMON,whichistheclosestavailablestandardresistor.
Sinceaccuratecurrentmonitoringisnotneededa25122terminalsenseresistorcanbeused.
Finally,computetheactualcurrentlimit(ILIM,CL)andtheanalogcurrentmonitoringscalingfactorVIMON,GAIN(VIMONvsILOAD)(15)sp(16)Figure19.
AddingRSTBLforVSNS,CL>67.
5mV10.
2.
3.
2SelectingtheFastTripThresholdandFilteringTheTPS2477xallowstheusertoprogramthefasttripthreshold.
Whenthisthresholdisexceededthegateisquicklypulleddown(PLIMsotheHotSwapwillstartinpowerlimitandtransitionintocurrentlimit.
Inthatcasethemaximumstarttimecanbecomputedasfollows:(24)Notethattheabovestart-timeisbasedontypicalcurrentlimitandpowerlimitvalues.
Toensurethatthetimernevertimesoutduringstart-upitisrecommendedtosetthefaulttime(TINR)tobe1.
5xtstart,maxor6ms.
Thiswillaccountforthevariationinpowerlimit,timercurrent,andtimercapacitance.
NextthedesignershoulddecideifhavingequalTINRandTFLTisacceptable.
Notethattopasstheloadtransientthefaulttimerneedstobelongerthan200ms.
Iftheinrushtimeisthislong,itwillplacetoomuchstressontheMOSFETduringastartintoshort.
Forthisreason,it'sidealtohavetwoseparatetimers.
Toensureproperstartupandtopasstheloadtransientatargetinrushtime(TINR,TGT)of6msandatargetfaulttime(TFLT,TGT)of250msisused.
CINR,CLCandCFLT,CLCiscomputedasfollows:(25)sp(26)ThenextlargestavailableCINRischosenas47nFandthenextlargestavailableCFLTischosenas2.
2FNext,theactualTINRandTFLTcanbecomputedasshownbelow:OncetheCTMRischosentheactualprogrammedtimeoutcanbecomputedasfollows.
(27)sp(28)10.
2.
3.
6CheckMOSFETSOAOncethepowerlimitandfaulttimerarechosen,it'scriticaltocheckthattheFETwillstaywithinitsSOAduringalltestconditions.
ForthisdesignexampletheTPS24772isused,whichdoesnotretryduringahot-short.
Thustheworstconditionisastart-upintoashortcircuit.
InthiscasetheTPS24772willstartintoapowerlimitandregulateatthatpointfor6.
2ms(TINR).
BasedontheSOAoftheCSD16415Q5B,itcanhandle13V,15Afor10msanditcanhandle13V,100Afor1ms.
TheSOAfor6.
2mscanbeextrapolatedbyapproximatingSOAvstimeasapowerfunctionasshownbelow:(29)Copyright2015,TexasInstrumentsIncorporated21TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cnNotethattheSOAofaMOSFETisspecifiedatacasetemperatureof25°C,whilethecasetemperaturecanbehotterduringastartintoashort.
ItisimportanttounderstandthehottesttemperaturethataMOSFETcanbeduringastart-up(TC,MAX,START).
Ifaboardhasbeenoffforawhileandthenit'sturnedonTA,MAXisagoodestimateforTC,MAX,START.
However,ifaboardisonandthengetspowercycledorahotboardisunpluggedandpluggedbackinTC,MAXshouldbeusedforTC,MAX,START.
Thiswilldependonsystemrequirements.
Forthisdesignexampleit'sassumedthattheboardcanonlybepluggedincoldandTA,MAXisusedtoestimateTC,MAX,START.
(30)BasedonthiscalculationtheMOSFETcanhandle17A,13Vfor6.
2msat55°Celevatedcasetemperature,butisonlyrequiredtohandle9Aduringastartintoshort.
Thusthereisgoodmarginandthiswillbearobustdesign.
Ingeneral,itisrecommendedthattheMOSFETcanhandle1.
3xmorethanwhatisrequiredduringahot-short.
Thisprovidesmargintocoverthevarianceofthepowerlimitandfaulttime.
10.
2.
3.
7ChooseUnderVoltageandOverVoltageSettingsTheTPS2477xhascomparatorswith1.
35VthresholdontheENHS,ENOR,andOVpins.
AresistordividercanbeusedtosetUndervoltageandOvervoltagethresholdsforthebus.
Forthisdesignexample10Vand14Vwerechosenasthelimitstoallowsomemarginforthe11Vto13Vinputbus.
Oncetheselimitsareknown,RDIV2andRDIV3canbecomputedusingtheequationsbelow.
RDIV1wassetto49.
9k,whichkeepsthepowerconsumptionreasonablelowwithoutbeingtoosusceptibletoleakagecurrents.
(31)sp(32)sp(33)Chooseclosestavailableresistorsstandard1%resistors:RDIV2=2.
21kandRDIV3=5.
62k.
TheactualUnderVoltageandOverVoltagesettingscanbecomputedforthechosenresistorsasfollows:(34)sp(35)10.
2.
3.
8SelectingC1andCOUTItisrecommendedtoaddceramicbypasscapacitorstohelpstabilizethevoltagesontheinputandoutput.
SinceCINwillbechargeddirectlyonhot-plug,itsvalueshouldbekeptsmall.
0.
1Fisagoodtarget.
SinceCOUTdoesn'tgetchargedduringhot-plug,alargervaluesuchas1Fcouldbeused.
10.
2.
3.
9AddingCENHSWhentheENHSpinispulledbelowitsthresholdandraisedbackuptheICwillreset.
NotethatduringahotshorttheinputvoltagecaneasilydroopbelowtheUVthresholdandcycletheENHSpin.
FortheTPS24770andTPS24771ICsthiswillnotchangethebehavior.
However,whenusingtheTPS24772thecyclingoftheENHSwillresultintheICattemptingtorestart,whichisundesired(thisisthemainreasonwhysomeonewouldusetheTPS24772).
ToavoidthisbehavioracapacitorshouldbeaddedtotheENHStoprovidefiltering.
33nFwaschosenforthisexample.
22Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH201510.
2.
3.
10SelectingD1andD2DuringhotplugandhotshorteventstherecouldbesignificanttransientsontheinputandoutputoftheHotSwapthatcouldcauseoperationoutsideoftheICspecifications.
ToensurereliableoperationaTVSontheinputandaSchottkeydiodeontheoutputarerecommended.
InthisexampleaSMDJ14AandMBRS330T3Gareused.
10.
2.
3.
11CheckingStabilityFormostapplications,theTPS2477xisstablewithoutanyadditionalcomponents.
HoweverinsomecasesadditionalCGS,EXTisrequiredasshowninthefollowingfiguretohelpstabilizethecurrentandpowerlimitloop.
Typicallythisisforlowcurrentlimitsandlowsensevoltages.
Itiseasytocheckwhethertheseextracomponentsareneededusingtheequationsbelow.
Notethatthetransconductance(alsoreferredtoasgmandgfs)oftheFETwillvarybasedonthecurrentandthusgm'isusedintheequationsasanormalizingparameter.
TheCSD16415Q5Bhasagmof168siemensat40AofIDS,resultingingm'of26.
56.
Forthisexample,CGS,MIN(perFET)wascomputedtobe0.
25nF,whiletheCISSoftheCSD16415Q5Bis3.
15nFprovidingplentyofmarginforthedesign.
Ingeneralitisrecommendedtohavea2xmarginfromthetypicalCISSandCGS,MINtoaccountforanyvariationthattheFETwouldhave.
IftheCISSoftheMOSFETisn'tlargeenoughanexternalRCshouldbeaddedasshowninthefigurebelow.
(36)(37)(38)Figure20.
AddingCGS,EXTtoEnsureStability10.
2.
3.
12ComputeTolerancesAfterfinishingadesignitisoftendesiredtoknowthevariationsofeachsetting.
Oftentimestherearemultipleerrorsourcesandtherearetwocommonwaystoanalyzethecircuit.
Oneisworstcase,whichaddsalloftheerrorsourcesandtheotheroneisrootsumsquare(RSS),whichislessconservative.
Whenerrorsourcesareindependent,usingtheRSSmethodprovidesamorestatisticallyaccurateviewofthetolerances.
Thismethodisusedinthissection.
Notethattheerrorcalculationsarequitelongandtediousandit'srecommendedtouseTI'sexceltools,whichsupportbothworstcaseandRSSanalysis.
Forthisexamplethebelowtolerancesareassumed.
Thefollowingtableliststheassumptionsforthecomponenttolerances.
Notethatthesenseresistoritselfis1%accurate,butmultipletwoterminal2512resistorsareusedsoadditionalerrorisintroducedfromsolderresistanceandlayoutlimitationsofparallelingresistors.
Forthisexample3%isassumedasthetotalerrorofthesensingnetwork.
Copyright2015,TexasInstrumentsIncorporated23TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cnTable2.
ComponentTolerancesCOMPONENTSTOLERANCERIMONandRSET1%RSNS(IncludingLayout+Soldering)3%RDIV1,RDIV2,RDIV3,RPLIM,RFST1%CINR,CFLT10%First,thetoleranceofthecurrentmonitoringandcurrentlimitiscomputed.
Thereare5errorsourcingcontributingtothecurrentmonitoringaccuracyontheIMONpin:toleranceofRSET(ERSET),toleranceofRIMON(ERIMON),toleranceofRSNS(ERSNS),theICgainerror(ERGAIN),andtheICoffseterror(EROS).
Alloftheseerrorsarein%withtheexceptionoftheoffseterror.
Togetapercenterrorduetotheoffseterror(EROS%)simplydividetheoffsetbythesensevoltage.
FortheTPS2477x,ERGAINis0.
4%,andEROSis150V.
Basedonthesevaluesthefullscale(IFS,ERR,IMON)currentmonitoringaccuracyattheImonpincanbecomputedwiththefollowingequations.
(39)NotethattheTPS2477xdetectsthecurrentlimitwhentheIMONpinexceeds675mV.
ThusthecurrentlimiterrorILIM,ERisacombinationoftheIFS,ERR,IMONandthecurrentlimiterrorattheIMONpin(ILIM,ERR,IMON).
The675mVthresholdvariesupto15mVsoILIM,ERR,IMONis2.
3%andthecurrentlimiterrorcanbecomputedasfollows:(40)Nextthepowerlimiterroriscomputed.
Thiserrorismadeupofthreesources:theerrorfromexternalcomponents(ERCOMP),theerrorwhentranslatingthesensevoltagetoIMON(IPL,ERR,IMON),andtheerrorofthepowerlimitengineatIMON(ERIMON,PL).
BothERSNSandERIMON,PLareafunctionoftheoperatingpointofthepowerlimitengine.
NotethatthiserrorisgreatestatlargestVDS,sinceVSNS,PLissmallest(refertoFigure12).
ForthisexampleVDSislargestwhenVIN=13V(maximumVIN)andVOUT=0Vandtheerroriscomputedatthisoperatingpoint.
Thesensevoltage(VSNS)andthevoltageattheIMONpin(VIMON)shouldbecomputedforthisoperatingpointusingtheequationsbelow:(41)sp(42)TheIPL,ERR,IMONcanbecomputedsimilarlytoIFS,ERR,IMONusingtheequationbelow.
sp(43)ThetoleranceofthepowerlimitengineisspecifiedatthreeVIMONpointsinthedatasheet:135mV(±20.
3mV),67.
5mV(±10.
1mV),and27mV(±8.
1mV).
Togetthe%errorattherealoperatingpoint,theabsoluteerrorshouldbeextrapolatedanddividedbyVIMONasshownintheequationbelow.
ThisisgraphicallydepictedinFigure23.
(44)24Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH2015Figure21.
ExtrapolatingPowerLimitErrorOnceERIMON,PLandIPL,ERR,IMONareknownthetotalpowerlimiterror(PLERR,TOT)canbecomputedusingtheequationbelow.
Thecomponenterror(3.
5%)comesfromRSNS(3%),RPLIM(1%),RSET(1%),andRIMON(1%).
(45)Aftercomputingthefasttripvoltagethresholdtobe24.
9mV(100A*249),thefasttripthresholderrorresultingfromtheIC(FSTERR,IC)canbecomputedusingasimilarextrapolationmethodasusedforpowerlimit.
ThecomponenterrorofRSNSandRFSTshouldbeaddedtoobtainthetotalfasttriperror(FSTERR,TOT).
Bothequationsareshownbelow.
(46)sp(47)TheICerroroftheUV/OVthresholdisalways3.
7%(0.
05V/1.
35V).
Assumingthatallresistorshavea1%errorthecomponenterroris1.
41%(2resistors).
WhenusingtheRSSmethodthetotalerroris4%.
Forthetimererror,theICcontributes22%and10%comesfromthecomponent.
WhenusingtheRSSmethodthetotalerrorbecomes24.
2%.
Thetablebelowsummarizesthefinaltolerancesofthedesign:Table3.
DesignTolerancesSETTINGSACCURACYCurrentLimit4.
1%FastTrip9.
4%PowerLimit20.
3%TFLT,TINR24.
2%UV/OV4.
0%Copyright2015,TexasInstrumentsIncorporated25TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn10.
2.
4ApplicationCurvesFigure22.
Startup(COUT=5500F)Figure23.
UndervoltageandOvervoltageFigure24.
StartUpwithOutputShortedtoGNDFigure25.
LoadStep100Ato120AFigure26.
HotShortonOutputwithFullLoadFigure27.
HotShortonOutputwithFullLoad(zoomedout)(zoomedin)26Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH2015Figure28.
HotShortonOutputwithNoLoad(zoomedout)Figure29.
HotShortonOutputwithNoLoad(zoomedin)10.
2.
5240VAApplicationUsingCSD16415Q5BThediagrambelowshowstheapplicationschematicforthisdesignexample.
SeetheTPS24770DesignCalculatortohelpwiththesecalculations.
Figure30.
ApplicationSchematicfor240VADesignwithCSD16415Q5B10.
2.
5.
1DesignRequirementsThefollowingtablesummarizestherequirementsforthisdesign.
Notethattheoutputpowercannotexceed240Wformorethan250ms.
Copyright2015,TexasInstrumentsIncorporated27TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cnTable4.
DesignRequirementsfora240VADesignusingCSD16415Q5BDESIGNPARAMETEREXAMPLEVALUEInputvoltagerange10.
8V–13.
2VOutputPowerLimit(VAlimiting)240WMaximumOutputCapacitanceoftheHotSwap2500uFMaximumAmbientTemperature55°CMOSFETRθCA(functionoflayout)35°C/WTransientloadrequirementPOUTisallowedtosurpass240Wfor<250msPass"Hot-Short"onOutputYesPassa"Startintoshort"YesIstheloadoffuntilPGassertedYesICusedTPS24772AnalogCurrentMonitorUsedNoMOSFETCSD16415Q5BCanaHotBoardbepluggedinorPowerCycledYes10.
2.
5.
2TheoryofOperationsBeforegoingintothedetailsofthedesignit'simportanttounderstandtheimpactthatRPOWhasonthecircuit.
RefertoFigure31forthisdiscussion.
Figure31.
ImpactofRPOWResistorNotethattheTPS2477xdetectsovercurrentconditionswhenVIMONreaches675mV,whichoccurswhenthereissufficientcurrent(iIMON)flowingthroughRIMON.
AlsonotethatiIMONisasumofiSETandiPOW.
IfiIMON,CL,iSET,CL,andiPOW,CLcorrespondtothesesamecurrentwhenVIMONreaches675mVandTPS2477xdetectscurrentlimit,thefollowingequationscanbewritten.
(48)(49)28Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH2015AlsonotethattheamplifierensuresthatSETandSENMareequalandthusILIMcanbederivedasfollows:(50)(51)Examiningtheequationabove,itcanbeseenthatILIMreducesasVINbecomeslarger.
Notethattheultimategoalistolimitoutputpower.
However,whentheFETison,VINisveryclosetoVOUTandtheycanbeassumedtobeequal.
ThefigurebelowcomparestheidealILIMvsVOUT(ILIM=240W/VOUT)profiletothatoftheRPOWimplementationshownhere.
Theerrorislargewhentheoutputvoltageisfarfrom12V,buttheperformanceisquitegoodnear12V.
Thenextfigureshowstheeffectiveoutputpowerlimitforoutputvoltagesfrom10Vto14V.
Itcanbeseenthattheresultsarequitegoodandmuchbetterthanusingasimple20Acurrentlimit,withouttheRPOWresistortocompensateforVINvariation.
Figure32.
CurrentLimit(withRPOW)vsOutputVoltageFigure33.
OutputPowerLimitingusingRPOWvsStandardILIM10.
2.
5.
3DesignProcedure10.
2.
5.
3.
1SelectVSNS,CL,RSNS,andRSETSettingForthisexample,VSNS,CLof10mVwasselectedtooptimizeefficiency.
ThenRSNScanbecomputedto0.
5m.
ThereissomeflexibilityinpickingtheRSETvalue.
Inthiscasetargeting100AforISET,CL,RSETiscomputedtobe100asshowninthefollowingequation.
(52)10.
2.
5.
3.
1.
1SelectRPOWandRIMONRPOWcontrolstheslopeoftheILIMvsVINcurveandthustheidealslopeshouldbefoundfirstbeforeselectingRPOW.
Thiscanbedonebytakingthederivativeoftheidealcurrentlimit(ILIM,IDEAL)vsVINcurveandevaluatingitat12V.
Thisisfoundtobe–1.
667A/Vasshownintheequationsbelow.
Nextthederivativeofequation51istakentoisolatethetermsthatinfluencetheslopeofILIMvsVINcurve.
SinceRSETandRSNShavealreadybeenselected,RPOWremainstheonlyparameterthatcanbevaried.
Thus,RPOWiscomputedusingthelastequationbelow.
(53)(54)Copyright2015,TexasInstrumentsIncorporated29TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn(55)TheclosestavailablestandardresistorischosenforRPOW,whichis121k.
NextRIMONshouldbechosentoensurethattheoutputpowerlimitis240Wat12V,whichisthetypicaloperatingpoint.
RIMONiscomputedtobe3.
49kandtheclosestavailablestandardresistorof3.
48kischosen.
(56)sp(57)10.
2.
5.
3.
1.
2SelectingtheHotSwapFET(s)ItiscriticaltoselectthecorrectMOSFETforaHotSwapdesign.
Thedevicemustmeetthefollowingrequirements:TheVDSratingshouldbesufficienttohandlethemaximumsystemvoltagealongwithanyringingcausedbytransients.
Formost12Vsystemsa25Vor30VFETisagoodchoice.
TheSOAoftheFETshouldbesufficienttohandleallusagecases:start-up,hot-short,startintoshort.
RDSONshouldbesufficientlylowtomaintainthejunctionandcasetemperaturebelowthemaximumratingoftheFET.
Infact,itisrecommendedtokeepthesteadystateFETtemperaturebelow125°Ctoallowmargintohandletransients.
Maximumcontinuouscurrentratingshouldbeabovethemaximumloadcurrentandthepulseddraincurrentmustbegreaterthanthecurrentthresholdofthecircuitbreaker.
MostMOSFETsthatpassthefirstthreerequirementswillalsopassthesetwo.
AVGSratingof+16Visrequired,becausetheTPS2477xcanpullupthegateashighas15.
5Vabovesource.
ForthisdesigntheCSD16415Q5BwasselectedforitslowRDSONandsuperiorSOA.
AfterselectingtheMOSFET,themaximumsteadystatecasetemperaturecanbecomputedasfollows:(58)IntheequationabovenisthenumberofFETsusedinparallel.
NotethattheRDSONisastrongfunctionofjunctiontemperature,whichformostMOSFETSwillbeveryclosetothecasetemperature.
AfewiterationsoftheaboveequationsmaybenecessarytoconvergeonthefinalRDSONandTC,MAXvalue.
AccordingtotheCSD16415Q5Bdatasheet,itsRDSONisabout1.
2xgreaterat75°Ccomparedtoroomtemperature.
.
TheequationbelowusesthisRDSONvaluetocomputetheTC,MAX.
NotethatthecomputedTC,MAXisclosetothejunctiontemperatureassumedforRDSON.
Thusnofurtheriterationsarenecessary.
(59)10.
2.
5.
3.
1.
3KeepingMOSFETwithinSOADuringNormalStart-upNext,thedesignermustensurethattheMOSFETwillstaywithinSOAduringstart-upandastart-upintoshort.
NotethattheTPS24772(fastlatchoff)isusedforthisdesignsotheMOSFETstressduringahotshortisminimal.
SinceRPOWbiasestheIMONpin,itinterfereswithFETpowerlimitingandit'srecommendedtodisableFETpowerlimitingitbyselectinga4.
99kresistorforRPOW.
30Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH2015TheinrushcurrentcanbelimitedbyaddingacapacitorfromHGATEtoGND(CDVDT)asshownintheapplicationdiagram.
ThiscapacitorlimitstheslewrateofHGATEatstart-up,whichwillinturnlimittheslewrateofVOUT.
AssumingthattheloadisoffuntilPGHSisasserted,alloftheinrushcurrentwouldbegoingintoCOUTandbeinverselyproportionaltotheslewrateofVOUT.
Refertotheapplicationplotsforastart-upwaveform.
Inaddition,a1kresistorisplacedinserieswithCDVDTtoensurethatCDVDTdoesn'tslowdowntheshortcircuitresponseoftheHotSwap.
Forthisexample,a100nFcapacitorwasusedforCDVDT.
Thisresultsinaninrushcurrent(IINR)of1.
375A,totalinrushtime(tINR)of24.
5,andpeakFETpowerdissipation(PFET,PEAK)of18.
7Wasshowninequationsbelow.
Thisassumesmaximuminputvoltageof13.
2V(60)sp(61)sp(62)Next,it'simportationtocheckthattheMOSFETcanhandlethisstresslevel.
NotethatthepowerdissipationoftheMOSFETwillstartatPINR,MAXandwillreducetozeroastheVDSdropacrosstheMOSFETreduces.
TheeffectivestressontheMOSFETcanbeapproximatedtobePINR,MAXfortINR/2,whichistheequivalentamountofenergy.
Forthisexample,theFETstressis18.
7Wfor12.
3ms.
LookingattheSOAcurveoftheCSD16415Q5B,atVDSof13.
2Vitcanhandle~15Afor10msor~4Afor100ms.
Usingthesamemethodasthepreviousdesignexample,itcanbecomputedthattheMOSFETcanhandle13.
4Afor12.
3mswhenVDS=13.
2V.
TheSOAofaMOSFETisspecifiedatacasetemperatureof25°C,whiletherealcasetemperaturecanbehotterduringastartintoashort.
ItisimportanttounderstandthehottesttemperaturethataMOSFETcanbeduringastart-up(TC,MAX,START).
Ifaboardhasbeenoffforawhileandthenit'sturnedon,TA,MAXisagoodestimateforTC,MAX,START.
However,ifaboardisonandthengetspowercycledorgetsunpluggedandpluggedbackin,TC,MAXshouldbeusedforTC,MAX,START.
Thiswilldependonsystemrequirements.
Forthisdesignexample,itisassumedthatahotboardcanbepowercycledorhotpluggedandthusTC,MAXisusedtoestimateTC,MAX,START.
(63)BasedonthiscalculationtheMOSFETcanhandle8.
4A,13.
2Vfor12.
3msat72°Celevatedcasetemperature,butisonlyrequiredtohandle1.
375A.
Thusthereisgoodmarginandthiswillbearobustdesign.
Ingenerala1.
3xmarginisrecommendedtocoverforvariations.
Next,thestartintoshortcaseisconsidered.
SincetheMOSFETpowerlimitisdisabled,thecurrentthroughtheMOSFETwillreach20Abeforethepartstartstoregulateandrunstheinrushtimer.
InordertominimizeFETstress,ashortinrushtimerischosen(1nFofCINR).
Unfortunately,whenaveryshorttimerisusedandthereisadv/dtcapacitor,theFETstresscannotbesimplyestimatedbyTINR.
Inthefollowingfigure,itisclearthattheFEThasbothvoltageandsignificantcurrentacrossitforlongerthanjustTINR.
ThisoccursbecauseTINRisonlyactivatedwhenIINreachesthecurrentlimitthreshold,whichdoesn'thappenimmediatelyduetotheslowdv/dtonthegateandthelimitedtransconductanceoftheFET.
Thecurrentisnotasquarepulse,whichmakesithardtocomparetheFETstresstotheSOAcurves.
Thusthestressshowninthefollowingfigureneedstobeconvertedtoanequivalentsquarepulse.
Forthisexample,theequivalentpulsewasassumedtobe20Afor1ms.
TheMOSFETcanhandle100A,13.
2Vfor1ms,whichcanbederatedto62Awhenaccountingforelevatedcasetemperature.
Thisprovidesplentyofmarginandensuresarobustdesign.
Copyright2015,TexasInstrumentsIncorporated31TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn(64)Figure34.
Start-upIntoShort10.
2.
5.
3.
1.
4ChooseFaultTimerTopasstheloadtransient,atargetfaulttime(TFLT,TGT)of250msisused.
CFLT,CLCiscomputedasfollows:sp(65)ThenextlargestavailableCFLTischosenas2.
2F,whichresultsinaTFLTof290msasshownbelow.
(66)10.
2.
5.
3.
1.
5ChooseUnderVoltageandOverVoltageSettingsForthisdesignexample10Vand14Vwerechosenasthelimitstoallowsomemarginforthe10.
8Vto13.
2Vinputbus.
Theseareidenticaltothepreviousdesignexample.
SeeChooseUnderVoltageandOverVoltageSettingssectionforprogrammingthesethresholds.
10.
2.
5.
3.
1.
6SelectingCINandCOUTItisrecommendedtoaddceramicbypasscapacitorstohelpstabilizethevoltagesontheinputandoutput.
SinceCINwillbechargeddirectlyonhot-plug,it'svalueshouldbekeptsmall.
0.
1Fisagoodtarget.
SinceCOUTdoesn'tgetchargedduringhot-plug,alargervaluesuchas1Fcouldbeused.
10.
2.
5.
3.
1.
7SelectingD1andD2DuringhotplugandhotshorteventstherecouldbesignificanttransientsontheinputandoutputoftheHotSwapthatcouldcauseoperationoutsideoftheICspecifications.
ToensurereliableoperationaTVSontheinputandaSchottkeydiodeontheoutputarerecommended.
InthisexampleaSMDJ14AandMBRS330T3Gareused.
32Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH201510.
2.
5.
3.
1.
8AddingCENHSWhentheENHSpulledbelowitsthresholdandraisedbackuptheICwillreset.
NotethatduringahotshorttheinputvoltagecaneasilydroopbelowtheUVthresholdandcycletheENHSpin.
FortheTPS24770andTPS24771ICsthiswillnotchangethebehavior.
However,whenusingtheTPS24772thecyclingoftheENHSwillresultintheICattemptingtorestart,whichisundesired(thisisthemainreasonwhysomeonewouldusetheTPS24772).
ToavoidthisbehavioracapacitorshouldbeaddedtotheENHStoprovidefiltering.
33nFwaschosenforthisexample.
10.
2.
5.
3.
1.
9StabilityConsiderationsSincethereisa100nFCDVDTattachedtoHGATE,thissignificantlyincreasestheeffectivecapacitanceofHGATEandguaranteesstabilityforthisapplication.
10.
2.
5.
4ApplicationCurvesFigure35.
NoLoadthenHotShort(ZoomedOut)Figure36.
FullLoadthenHotShort(ZoomedIn)Figure37.
OvercurrentFigure38.
StartUpintoShortCopyright2015,TexasInstrumentsIncorporated33TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cnFigure39.
Startup(COUT=2500F)Figure40.
StartupshowingPGHSandFLTb(COUT=2500F)Figure41.
UnderVoltageandOverVoltagewithVINRising34Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH201510.
2.
6240VAApplicationUsingCSD17573Q5BThisdesignexamplehasidenticalrequirementstothepreviousone,buttheCSD17573Q5BisusedinsteadoftheCSD16415Q5B.
TheCSD17573Q5BischeaperandoffersbetterRDSON,butitsSOAisnotasgood.
ThusitwasnecessarytoaddQ2andRSET2toreducethestressduringastartupintoashortcircuit.
GiventhatQ2isasmallsignalPFETthatischeap,theoverallBOMcostofthissolutionshouldbecheaperthanthepreviousone.
SeetheTPS24770DesignCalculatortohelpwiththesecalculations.
Figure42.
240VADesignUsingCSD17573Q5BCopyright2015,TexasInstrumentsIncorporated35TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn10.
2.
6.
1DesignRequirementsThefollowingtablesummarizestherequirementsforthisdesign.
Table5.
DesignRequirementsforthe240VADesignUsingCSD17573Q5BDESIGNPARAMETEREXAMPLEVALUEInputvoltagerange10.
8V–13.
2VOutputPowerLimit(VAlimiting)240WMaximumOutputCapacitanceoftheHotSwap2500FMaximumAmbientTemperature55°CMOSFETRθCA(functionoflayout)35°C/WTransientloadrequirementPOUTisallowedtosurpass240Wfor<250msPass"Hot-Short"onOutputYesPassa"Startintoshort"YesIstheloadoffuntilPGisassertedYesICusedTPS24772AnalogCurrentMonitorUsedNoMOSFETCSD17573Q5BCanaHotBoardbepluggedinorPowerCycledYes10.
2.
6.
1.
1ChoosingC1,COUT,CFLT,CENHS,D1,D2,RSET,RPOW,RIMON,RSNS,CDVDT,RPLIM,andUV/OVThresholdsThesecomponentsandsettingsarechoseninthesamefashionasthepreviousdesignexample.
See240VAApplicationUsingCSD16415Q5B.
10.
2.
6.
1.
2SelectingtheHotSwapFET(s)ItiscriticaltoselectthecorrectMOSFETforaHotSwapdesign.
Thedevicemustmeetthefollowingrequirements:TheVDSratingshouldbesufficienttohandlethemaximumsystemvoltagealongwithanyringingcausedbytransients.
Formost12Vsystemsa25Vor30VFETisagoodchoice.
TheSOAoftheFETshouldbesufficienttohandleallusagecases:start-up,hot-short,startintoshort.
RDSONshouldbesufficientlylowtomaintainthejunctionandcasetemperaturebelowthemaximumratingoftheFET.
Infact,itisrecommendedtokeepthesteadystateFETtemperaturebelow125°Ctoallowmargintohandletransients.
Maximumcontinuouscurrentratingshouldbeabovethemaximumloadcurrentandthepulseddraincurrentmustbegreaterthanthecurrentthresholdofthecircuitbreaker.
MostMOSFETsthatpassthefirstthreerequirementswillalsopassthesetwo.
AVGSratingof+16Visrequired,becausetheTPS2477xcanpullupthegateashighas15.
5Vabovesource.
ForthisdesigntheCSD17573Q5BwasselectedforitslowRDSONandgreatcostpoint.
AfterselectingtheMOSFET,themaximumsteadystatecasetemperaturecanbecomputedasfollows:(67)IntheequationabovenisthenumberofFETsusedinparallel.
NotethattheRDSONisastrongfunctionofjunctiontemperature,whichformostMOSFETSwillbeveryclosetothecasetemperature.
AfewiterationsoftheaboveequationsmaybenecessarytoconvergeonthefinalRDSONandTC,MAXvalue.
AccordingtotheCSD17573Q5Bdatasheet,itsRDSONisabout1.
2xgreaterat65°Ccomparedtoroomtemperature.
TheequationbelowusesthisRDSONvaluetocomputetheTC,MAX.
NotethatthecomputedTC,MAXisclosetothejunctiontemperatureassumedforRDSON.
Thusnofurtheriterationsarenecessary.
(68)36Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH201510.
2.
6.
1.
3KeepingtheMOSFETwithinSOAAsinthepreviousexample,itisimportanttoensurethattheMOSFETstayswithinitsSOAduringbothregularstart-upandstart-upintoshort.
Firstconsidertheregularstart-up.
ThesameCDVDTisusedasthelastexamplesotheFETisrequiredtohandle18.
2W(or1.
38Aand13.
2V)for12.
3ms.
BasedontheSOAcurveoftheCSD17573Q55B,atVDSof13.
2Vitcanhandle4.
5Afor10msor2Afor100ms.
Usingthesamemethodasthepreviousdesignexample,itcanbeinferredthattheMOSFETcanhandle4.
2Afor12.
3mswhenVDS=13.
2V.
TheSOAofaMOSFETisspecifiedatacasetemperatureof25°C,whilethecasetemperaturecanbehotterduringastartintoashort.
ItisimportanttounderstandthehottesttemperaturethataMOSFETcanbeduringastart-up(TC,MAX,START).
Ifaboardhasbeenoffforawhileandthenit'sturnedonTA,MAXisagoodestimateforTC,MAX,START.
However,ifaboardisonandthengetspowercycledTC,MAXshouldbeusedforTC,MAX,START.
Thiswilldependonsystemrequirements.
Forthisdesignexample,it'sassumedthatahotboardcanbepowercycledorhotpluggedandTC,MAXisusedtoestimateTC,MAX,START.
(69)BasedonthiscalculationtheMOSFETcanhandle2.
7A,13.
2Vfor12.
3msat69°Celevatedcasetemperature,butisonlyrequiredtohandle1.
38A.
Thusthereissufficientmargintomakethisarobustdesign.
Againa1.
3xmarginisrecommendedtocoverforvariations.
Next,considerthestartintoshortcondition.
SimilartothepreviousdesigntheMOSFETwouldneedtohandle20Aand13.
2Vfor~1ms.
CheckingtheSOAcurveoftheCSD17573Q5B,itcanonlyhandle10Aand13.
2Vfor1ms,soit'sSOAisclearlynotsufficient.
ThisiswhereQ2andRSET2comein.
Theyservetoreducethecurrentlimitduringstartingup(ILIM,START)whiletheVDSoftheHotSwapMOSFETisaboveVTofQ2(1Vto2V).
TheratioofILIMtoILIM,START,denotedasIRATIO,isafunctionofRSETandRSET2asshownbelow.
Forthisexamplearatioof0.
2(ILIM,START=4A)wastargetedtoreduceMOSFETstress,keepthecurrentlimitaboveIINR,andensuresufficientsignalonVSNStokeeptheerrorreasonable.
OnceIRATIOischosen,RSET2iscomputedtobe25asshownbelow.
(70)(71)Thestart-upintoshort(withRSET2andQ2)isshowninFigure43below.
Theequivalentpowerpulseisnow4Afor~0.
5ms.
TheMOSFETcanhandle10A,13.
2Vfor1ms,whichcanbederatedto6.
5Awhenaccountingforelevatedcasetemperature.
SincetheMOSFETisonlyrequiredtohandle4Afor0.
5msthereisplentyofmargininthedesign.
(72)Copyright2015,TexasInstrumentsIncorporated37TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cnFigure43.
Start-upIntoShort(withRSETandQ2)10.
2.
6.
2Q2SelectionThereisalotofflexibilitywhenselectingQ2.
AnyPMOSwitha±20VVGSratingand20VofVDSratingissufficient.
ForthisexampleIRLML5203PbFwasused.
Notethatthe100kseriesresistoralongwiththeCISSofQ2(~500pF)forafilterwitha50stimeconstant.
ThisprotectsQ2incasethereishighfrequencyringingonVINthatcausesVIN–VOUTtoexceed20V.
Thiswillusuallyhappenedduringhot-plugorhot-short.
10.
2.
6.
3ApplicationCurvesFigure44.
FullLoadthenHotShort(ZoomedOut)Figure45.
FullLoadthenHotShort(ZoomedIn)38Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH2015Figure46.
OverCurrentFigure47.
StartUpIntoShortFigure48.
Startup(COUT=2500F)Figure49.
StartupshowingPGHSandFLTb(COUT=2500F)Figure50.
Copyright2015,TexasInstrumentsIncorporated39TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn11PowerSupplyRecommendationsIngeneral,operationisbestwhentheinputsupplyisn'tnoisyanddoesn'thavesignificanttransients.
Fornoisierenvironmentsfilteringoninput,output,andfasttripshouldbeadjustedtoavoidnuisancetrips.
12Layout12.
1LayoutGuidelinesWhendoingthelayoutoftheTPS2477xthefollowingareconsideredbestpractice.
EnsureproperKelvinSenseofRSNS.
KeepthefilteringcapacitorCFSTPasclosetotheICaspossible.
PlaceaShottkydiodeandaceramicbypasscapacitorclosetothesourceoftheHotSwapMOSFETDonotconnectVDDtotheKelvinSensetraceforSETandFSTPNotethatspecialcaremustbetakenwhenplacingthebypasscapacitorfortheVDDpin.
DuringHotShorts,thereisaverylargedv/dtoninputvoltageduringtheMOSFETturnoff.
IfthebypasscapacitorisplacedrightnexttothepinandthetracefromRSNStothepinislong,anLCfilterisformed.
AsaresultalargedifferentialvoltagecandevelopbetweenVDDandSENMifthereisalargetransientonVin.
ThiscouldresultinaviolationoftheabsmaxratingfromVDDtoSENM.
Toavoidthis,placethebypasscapacitorclosetoRSNSinsteadoftheVDDpin.
Figure51.
LayoutDon'tWhenusingparallelresistorsthelayoutbecomesevenmorecritical.
DuetoPCBparasitics,thecurrentthrougheachRSNSmaybedifferent,whichresultsindifferentsensevoltagesacrossthetworesistors.
It'simportanttoaveragetheseinordertogetapropercurrentmeasurement.
Thiscanbeaccomplishedbyformingaresistordividerwiththetraces.
AslongasDis1=Dis2,thefinalVSNSwillbeanaverageofthedropacrossthetworesistors.
40Copyright2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH2015LayoutGuidelines(continued)Figure52.
SenseLayoutwith2RSNS版权2015,TexasInstrumentsIncorporated41TPS24772TPS24771TPS24770ZHCSDK8–MARCH2015www.
ti.
com.
cn12.
2LayoutExample42版权2015,TexasInstrumentsIncorporatedTPS24772TPS24771TPS24770www.
ti.
com.
cnZHCSDK8–MARCH201513器器件件和和文文档档支支持持13.
1相相关关链链接接以下表格列出了快速访问链接.
范围包括技术文档、支持与社区资源、工具和软件,并且可以快速访问样片或购买链接.
表表6.
相相关关链链接接器器件件产产品品文文件件夹夹样样片片与与购购买买技技术术文文档档工工具具与与软软件件支支持持与与社社区区TPS24770请单击此处请单击此处请单击此处请单击此处请单击此处TPS24771请单击此处请单击此处请单击此处请单击此处请单击此处TPS24772请单击此处请单击此处请单击此处请单击此处请单击此处13.
2商商标标Alltrademarksarethepropertyoftheirrespectiveowners.
13.
3静静电电放放电电警警告告这些装置包含有限的内置ESD保护.
存储或装卸时,应将导线一起截短或将装置放置于导电泡棉中,以防止MOS门极遭受静电损伤.
13.
4术术语语表表SLYZ022—TI术语表.
这份术语表列出并解释术语、首字母缩略词和定义.
14机机械械、、封封装装和和可可订订购购信信息息以下页中包括机械、封装和可订购信息.
这些信息是针对指定器件可提供的最新数据.
这些数据会在无通知且不对本文档进行修订的情况下发生改变.
欲获得该数据表的浏览器版本,请查阅左侧的导航栏.
版权2015,TexasInstrumentsIncorporated43重重要要声声明明德州仪器(TI)及其下属子公司有权根据JESD46最新标准,对所提供的产品和服务进行更正、修改、增强、改进或其它更改,并有权根据JESD48最新标准中止提供任何产品和服务.
客户在下订单前应获取最新的相关信息,并验证这些信息是否完整且是最新的.
所有产品的销售都遵循在订单确认时所提供的TI销售条款与条件.
TI保证其所销售的组件的性能符合产品销售时TI半导体产品销售条件与条款的适用规范.
仅在TI保证的范围内,且TI认为有必要时才会使用测试或其它质量控制技术.
除非适用法律做出了硬性规定,否则没有必要对每种组件的所有参数进行测试.
TI对应用帮助或客户产品设计不承担任何义务.
客户应对其使用TI组件的产品和应用自行负责.
为尽量减小与客户产品和应用相关的风险,客户应提供充分的设计与操作安全措施.
TI不对任何TI专利权、版权、屏蔽作品权或其它与使用了TI组件或服务的组合设备、机器或流程相关的TI知识产权中授予的直接或隐含权限作出任何保证或解释.
TI所发布的与第三方产品或服务有关的信息,不能构成从TI获得使用这些产品或服务的许可、授权、或认可.
使用此类信息可能需要获得第三方的专利权或其它知识产权方面的许可,或是TI的专利权或其它知识产权方面的许可.
对于TI的产品手册或数据表中TI信息的重要部分,仅在没有对内容进行任何篡改且带有相关授权、条件、限制和声明的情况下才允许进行复制.
TI对此类篡改过的文件不承担任何责任或义务.
复制第三方的信息可能需要服从额外的限制条件.
在转售TI组件或服务时,如果对该组件或服务参数的陈述与TI标明的参数相比存在差异或虚假成分,则会失去相关TI组件或服务的所有明示或暗示授权,且这是不正当的、欺诈性商业行为.
TI对任何此类虚假陈述均不承担任何责任或义务.
客户认可并同意,尽管任何应用相关信息或支持仍可能由TI提供,但他们将独力负责满足与其产品及在其应用中使用TI产品相关的所有法律、法规和安全相关要求.
客户声明并同意,他们具备制定与实施安全措施所需的全部专业技术和知识,可预见故障的危险后果、监测故障及其后果、降低有可能造成人身伤害的故障的发生机率并采取适当的补救措施.
客户将全额赔偿因在此类安全关键应用中使用任何TI组件而对TI及其代理造成的任何损失.
在某些场合中,为了推进安全相关应用有可能对TI组件进行特别的促销.
TI的目标是利用此类组件帮助客户设计和创立其特有的可满足适用的功能安全性标准和要求的终端产品解决方案.
尽管如此,此类组件仍然服从这些条款.
TI组件未获得用于FDAClassIII(或类似的生命攸关医疗设备)的授权许可,除非各方授权官员已经达成了专门管控此类使用的特别协议.
只有那些TI特别注明属于军用等级或"增强型塑料"的TI组件才是设计或专门用于军事/航空应用或环境的.
购买者认可并同意,对并非指定面向军事或航空航天用途的TI组件进行军事或航空航天方面的应用,其风险由客户单独承担,并且由客户独力负责满足与此类使用相关的所有法律和法规要求.
TI已明确指定符合ISO/TS16949要求的产品,这些产品主要用于汽车.
在任何情况下,因使用非指定产品而无法达到ISO/TS16949要求,TI不承担任何责任.
产品应用数字音频www.
ti.
com.
cn/audio通信与电信www.
ti.
com.
cn/telecom放大器和线性器件www.
ti.
com.
cn/amplifiers计算机及周边www.
ti.
com.
cn/computer数据转换器www.
ti.
com.
cn/dataconverters消费电子www.
ti.
com/consumer-appsDLP产品www.
dlp.
com能源www.
ti.
com/energyDSP-数字信号处理器www.
ti.
com.
cn/dsp工业应用www.
ti.
com.
cn/industrial时钟和计时器www.
ti.
com.
cn/clockandtimers医疗电子www.
ti.
com.
cn/medical接口www.
ti.
com.
cn/interface安防应用www.
ti.
com.
cn/security逻辑www.
ti.
com.
cn/logic汽车电子www.
ti.
com.
cn/automotive电源管理www.
ti.
com.
cn/power视频和影像www.
ti.
com.
cn/video微控制器(MCU)www.
ti.
com.
cn/microcontrollersRFID系统www.
ti.
com.
cn/rfidsysOMAP应用处理器www.
ti.
com/omap无线连通性www.
ti.
com.
cn/wirelessconnectivity德州仪器在线技术支持社区www.
deyisupport.
comIMPORTANTNOTICE邮寄地址:上海市浦东新区世纪大道1568号,中建大厦32楼邮政编码:200122Copyright2015,德州仪器半导体技术(上海)有限公司PACKAGEOPTIONADDENDUMwww.
ti.
com19-Apr-2015Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Lead/BallFinish(6)MSLPeakTemp(3)OpTemp(°C)DeviceMarking(4/5)SamplesTPS24770RGERACTIVEVQFNRGE243000Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to125TPS24770TPS24770RGETACTIVEVQFNRGE24250Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to125TPS24770TPS24771RGERACTIVEVQFNRGE243000Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to125TPS24771TPS24771RGETACTIVEVQFNRGE24250Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to125TPS24771TPS24772RGERACTIVEVQFNRGE243000Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to125TPS24772TPS24772RGETACTIVEVQFNRGE24250Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to125TPS24772(1)Themarketingstatusvaluesaredefinedasfollows:ACTIVE:Productdevicerecommendedfornewdesigns.
LIFEBUY:TIhasannouncedthatthedevicewillbediscontinued,andalifetime-buyperiodisineffect.
NRND:Notrecommendedfornewdesigns.
Deviceisinproductiontosupportexistingcustomers,butTIdoesnotrecommendusingthispartinanewdesign.
PREVIEW:Devicehasbeenannouncedbutisnotinproduction.
Samplesmayormaynotbeavailable.
OBSOLETE:TIhasdiscontinuedtheproductionofthedevice.
(2)EcoPlan-Theplannedeco-friendlyclassification:Pb-Free(RoHS),Pb-Free(RoHSExempt),orGreen(RoHS&noSb/Br)-pleasecheckhttp://www.
ti.
com/productcontentforthelatestavailabilityinformationandadditionalproductcontentdetails.
TBD:ThePb-Free/Greenconversionplanhasnotbeendefined.
Pb-Free(RoHS):TI'sterms"Lead-Free"or"Pb-Free"meansemiconductorproductsthatarecompatiblewiththecurrentRoHSrequirementsforall6substances,includingtherequirementthatleadnotexceed0.
1%byweightinhomogeneousmaterials.
Wheredesignedtobesolderedathightemperatures,TIPb-Freeproductsaresuitableforuseinspecifiedlead-freeprocesses.
Pb-Free(RoHSExempt):ThiscomponenthasaRoHSexemptionforeither1)lead-basedflip-chipsolderbumpsusedbetweenthedieandpackage,or2)lead-baseddieadhesiveusedbetweenthedieandleadframe.
ThecomponentisotherwiseconsideredPb-Free(RoHScompatible)asdefinedabove.
Green(RoHS&noSb/Br):TIdefines"Green"tomeanPb-Free(RoHScompatible),andfreeofBromine(Br)andAntimony(Sb)basedflameretardants(BrorSbdonotexceed0.
1%byweightinhomogeneousmaterial)(3)MSL,PeakTemp.
-TheMoistureSensitivityLevelratingaccordingtotheJEDECindustrystandardclassifications,andpeaksoldertemperature.
(4)Theremaybeadditionalmarking,whichrelatestothelogo,thelottracecodeinformation,ortheenvironmentalcategoryonthedevice.
(5)MultipleDeviceMarkingswillbeinsideparentheses.
OnlyoneDeviceMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireDeviceMarkingforthatdevice.
PACKAGEOPTIONADDENDUMwww.
ti.
com19-Apr-2015Addendum-Page2(6)Lead/BallFinish-OrderableDevicesmayhavemultiplematerialfinishoptions.
Finishoptionsareseparatedbyaverticalruledline.
Lead/BallFinishvaluesmaywraptotwolinesifthefinishvalueexceedsthemaximumcolumnwidth.
ImportantInformationandDisclaimer:TheinformationprovidedonthispagerepresentsTI'sknowledgeandbeliefasofthedatethatitisprovided.
TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.
Effortsareunderwaytobetterintegrateinformationfromthirdparties.
TIhastakenandcontinuestotakereasonablestepstoproviderepresentativeandaccurateinformationbutmaynothaveconducteddestructivetestingorchemicalanalysisonincomingmaterialsandchemicals.
TIandTIsuppliersconsidercertaininformationtobeproprietary,andthusCASnumbersandotherlimitedinformationmaynotbeavailableforrelease.
InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTItoCustomeronanannualbasis.
重重要要声声明明德州仪器(TI)及其下属子公司有权根据JESD46最新标准,对所提供的产品和服务进行更正、修改、增强、改进或其它更改,并有权根据JESD48最新标准中止提供任何产品和服务.
客户在下订单前应获取最新的相关信息,并验证这些信息是否完整且是最新的.
所有产品的销售都遵循在订单确认时所提供的TI销售条款与条件.
TI保证其所销售的组件的性能符合产品销售时TI半导体产品销售条件与条款的适用规范.
仅在TI保证的范围内,且TI认为有必要时才会使用测试或其它质量控制技术.
除非适用法律做出了硬性规定,否则没有必要对每种组件的所有参数进行测试.
TI对应用帮助或客户产品设计不承担任何义务.
客户应对其使用TI组件的产品和应用自行负责.
为尽量减小与客户产品和应用相关的风险,客户应提供充分的设计与操作安全措施.
TI不对任何TI专利权、版权、屏蔽作品权或其它与使用了TI组件或服务的组合设备、机器或流程相关的TI知识产权中授予的直接或隐含权限作出任何保证或解释.
TI所发布的与第三方产品或服务有关的信息,不能构成从TI获得使用这些产品或服务的许可、授权、或认可.
使用此类信息可能需要获得第三方的专利权或其它知识产权方面的许可,或是TI的专利权或其它知识产权方面的许可.
对于TI的产品手册或数据表中TI信息的重要部分,仅在没有对内容进行任何篡改且带有相关授权、条件、限制和声明的情况下才允许进行复制.
TI对此类篡改过的文件不承担任何责任或义务.
复制第三方的信息可能需要服从额外的限制条件.
在转售TI组件或服务时,如果对该组件或服务参数的陈述与TI标明的参数相比存在差异或虚假成分,则会失去相关TI组件或服务的所有明示或暗示授权,且这是不正当的、欺诈性商业行为.
TI对任何此类虚假陈述均不承担任何责任或义务.
客户认可并同意,尽管任何应用相关信息或支持仍可能由TI提供,但他们将独力负责满足与其产品及在其应用中使用TI产品相关的所有法律、法规和安全相关要求.
客户声明并同意,他们具备制定与实施安全措施所需的全部专业技术和知识,可预见故障的危险后果、监测故障及其后果、降低有可能造成人身伤害的故障的发生机率并采取适当的补救措施.
客户将全额赔偿因在此类安全关键应用中使用任何TI组件而对TI及其代理造成的任何损失.
在某些场合中,为了推进安全相关应用有可能对TI组件进行特别的促销.
TI的目标是利用此类组件帮助客户设计和创立其特有的可满足适用的功能安全性标准和要求的终端产品解决方案.
尽管如此,此类组件仍然服从这些条款.
TI组件未获得用于FDAClassIII(或类似的生命攸关医疗设备)的授权许可,除非各方授权官员已经达成了专门管控此类使用的特别协议.
只有那些TI特别注明属于军用等级或"增强型塑料"的TI组件才是设计或专门用于军事/航空应用或环境的.
购买者认可并同意,对并非指定面向军事或航空航天用途的TI组件进行军事或航空航天方面的应用,其风险由客户单独承担,并且由客户独力负责满足与此类使用相关的所有法律和法规要求.
TI已明确指定符合ISO/TS16949要求的产品,这些产品主要用于汽车.
在任何情况下,因使用非指定产品而无法达到ISO/TS16949要求,TI不承担任何责任.
产产品品应应用用数字音频www.
ti.
com.
cn/audio通信与电信www.
ti.
com.
cn/telecom放大器和线性器件www.
ti.
com.
cn/amplifiers计算机及周边www.
ti.
com.
cn/computer数据转换器www.
ti.
com.
cn/dataconverters消费电子www.
ti.
com/consumer-appsDLP产品www.
dlp.
com能源www.
ti.
com/energyDSP-数字信号处理器www.
ti.
com.
cn/dsp工业应用www.
ti.
com.
cn/industrial时钟和计时器www.
ti.
com.
cn/clockandtimers医疗电子www.
ti.
com.
cn/medical接口www.
ti.
com.
cn/interface安防应用www.
ti.
com.
cn/security逻辑www.
ti.
com.
cn/logic汽车电子www.
ti.
com.
cn/automotive电源管理www.
ti.
com.
cn/power视频和影像www.
ti.
com.
cn/video微控制器(MCU)www.
ti.
com.
cn/microcontrollersRFID系统www.
ti.
com.
cn/rfidsysOMAP应用处理器www.
ti.
com/omap无线连通性www.
ti.
com.
cn/wirelessconnectivity德州仪器在线技术支持社区www.
deyisupport.
comIMPORTANTNOTICEMailingAddress:TexasInstruments,PostOfficeBox655303,Dallas,Texas75265Copyright2015,TexasInstrumentsIncorporated