VUVLO51book.com

bq24171www.
ti.
comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013JEITACompliantStand-AloneSwitch-ModeLi-IonandLi-PolymerBatteryChargerwithIntegratedMOSFETsandPowerPathSelectorCheckforSamples:bq241711FEATURESAPPLICATIONSJEITACompatibleBatteryTemperatureTabletPCSensingNetbookandUltra-MobileComputers1.
6MHzSynchronousSwitch-ModeChargerPortableDataCaptureTerminalswith4AIntegratedN-MOSFETsPortablePrintersUpto94%EfficiencyMedicalDiagnosticsEquipment30VInputRatingwithAdjustableOver-VoltageBatteryBayChargersProtectionBatteryBack-UpSystems–4.
5Vto17VInputOperatingVoltageBatteryChargeVoltageDESCRIPTION–1,2,or3-Cellwith4.
2V/CellThebq24171ishighlyintegratedstand-aloneLi-ionandLi-polymerswitch-modebatterychargerwithtwoHighIntegrationintegratedN-channelpowerMOSFETs.
Itoffersa–AutomaticPowerPathSelectorBetweenconstant-frequencysynchronousPWMcontrollerwithAdapterandBatteryhighaccuracyregulationofinputcurrent,charge–DynamicPowerManagementcurrent,andvoltage.
ItcloselymonitorsthebatterypacktemperatureandallowschargeonlyinaJEITA–Integrated20-VSwitchingMOSFETsprofilecompatiblewindowwithlowerchargerateat–IntegratedBootstrapDiodelowtemperatureandlowerchargevoltageathigh–InternalLoopCompensationtemperature.
Italsoprovidesbatterydetection,pre-conditioning,chargetermination,andchargestatus–InternalDigitalSoftStartmonitoring.
ThethermalregulationloopreducesSafetychargecurrenttomaintainthejunctiontemperatureof–ThermalRegulationLoopThrottlesBack120°Cduringoperation.
CurrenttoLimitTj=120°CThebq24171chargesthebatteryinthreephases:–ThermalShutdownpreconditioning,constantcurrent,andconstant–BatteryThermistorSenseHot/ColdChargevoltage.
ItisadjustableforuptothreeseriesLi+Suspend&BatteryDetectcells.
–InputOver-VoltageProtectionwithChargeisterminatedwhenthecurrentreaches10%ProgrammableThresholdofthefastchargerate.
Aprogrammablechargetimeroffersasafetybackup.
Thebq24171automatically–Cycle-by-CycleCurrentLimitrestartsthechargecycleifthebatteryvoltagefallsAccuracybelowaninternalthreshold,andentersalow-–±0.
5%ChargeVoltageRegulationquiescentcurrentsleepmodewhentheinputvoltagefallsbelowthebatteryvoltage.
–±4%ChargeCurrentRegulation–±4%InputCurrentRegulationThebq24171featuresDynamicPowerManagement(DPM)toreducethechargecurrentwhentheinputLessthan15μABatteryCurrentwithAdapterpowerlimitisreachedtoavoidover-loadingtheRemovedadapter.
Ahighly-accuratecurrent-senseamplifierLessthan1.
5mAInputCurrentwithAdapterenablesprecisemeasurementofinputcurrentfromPresentandChargeDisabledadaptertomonitoroverallsystempower.
SmallQFNPackage–3.
5mm*5.
5mmQFN-24Pin1Pleasebeawarethatanimportantnoticeconcerningavailability,standardwarranty,anduseincriticalapplicationsofTexasInstrumentssemiconductorproductsanddisclaimerstheretoappearsattheendofthisdatasheet.
PRODUCTIONDATAinformationiscurrentasofpublicationdate.
Copyright2011–2013,TexasInstrumentsIncorporatedProductsconformtospecificationsperthetermsoftheTexasInstrumentsstandardwarranty.
Productionprocessingdoesnotnecessarilyincludetestingofallparameters.
bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
ti.
comThesedeviceshavelimitedbuilt-inESDprotection.
TheleadsshouldbeshortedtogetherorthedeviceplacedinconductivefoamduringstorageorhandlingtopreventelectrostaticdamagetotheMOSgates.
DESCRIPTION(CONTINUED)Thebq24171providespowerpathselectorgatedriverACDRV/CMSRConinputNMOSpairACFET(Q1)andRBFET(Q2),andBATDRVonabatteryPMOSdevice(Q3).
Whenthequalifiedadapterispresent,thesystemisdirectlyconnectedtotheadapter.
Otherwise,thesystemisconnectedtothebattery.
Inaddition,thepowerpathpreventsbatteryfromboostingbacktotheinput.
Thebq24171chargesbatteryfromDCsourceashighas17V,includingcarbattery.
Theinputover-voltagelimitisadjustablethroughOVPSETpin.
TheAVCC,ACPandACNpinsare30Vrating.
Whenahigh-voltageDCsourceisinserted,Q1/Q2remainofftoavoidhigh-voltagedamagetothesystem.
For1cellapplications,ifthebatteryisnotremovable,thesystemcanbedirectlyconnectedtothebatterytosimplifythepowerpathdesignandlowerthecost.
Withthisconfiguration,thebatterycanautomaticallysupplementthesystemloadiftheadapterisoverloaded.
Thebq24171isavailableina24-pin,3.
5mmx5.
5mmthinQFNpackage.
RGYPACKAGE(TOPVIEW)PINFUNCTIONSPINTYPEDESCRIPTIONNO.
NAME1,24SWPSwitchingnode,chargecurrentoutputinductorconnection.
Connectthe0.
047-FbootstrapcapacitorfromSWtoBTST.
2,3PVCCPChargerinputvoltage.
Connectatleast10-FceramiccapacitorfromPVCCtoPGNDandplaceitascloseaspossibletoIC.
4AVCCPICpowerpositivesupply.
Placea1-FceramiccapacitorfromAVCCtoAGNDandplaceitascloseaspossibletoIC.
Placea10-ΩresistorfrominputsidetoAVCCpintofilterthenoise.
For5Vinput,a5-Ωresistorisrecommended.
5ACNIAdaptercurrentsenseresistornegativeinput.
A0.
1-FceramiccapacitorisplacedfromACNtoACPtoprovidedifferential-modefiltering.
Anoptional0.
1-FceramiccapacitorisplacedfromACNpintoAGNDforcommon-modefiltering.
6ACPP/IAdaptercurrentsenseresistorpositiveinput.
A0.
1-FceramiccapacitorisplacedfromACNtoACPtoprovidedifferential-modefiltering.
A0.
1-FceramiccapacitorisplacedfromACPpintoAGNDforcommon-modefiltering.
7CMSRCOConnecttocommonsourceofN-channelACFETandreverseblockingMOSFET(RBFET).
Place4-kΩresistorfromCMSRCpintothecommonsourceofACFETandRBFETtocontroltheturn-onspeed.
TheresistancebetweenACDRVandCMSRCshouldbe500-kΩorbigger.
2SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013PINFUNCTIONS(continued)PINTYPEDESCRIPTIONNO.
NAME8ACDRVOACadaptertosystemswitchdriveroutput.
Connectto4-kΩresistorthentothegateoftheACFETN-channelpowerMOSFETandthereverseconductionblockingN-channelpowerMOSFET.
ConnectbothFETsascommon-source.
Theinternalgatedriveisasymmetrical,allowingaquickturn-offandslowerturn-oninadditiontotheinternalbreak-before-makelogicwithrespecttotheBATDRV.
9STATOOpen-drainchargestatuspinwith10-kΩpulluptopowerrail.
TheSTATpincanbeusedtodriveLEDorcommunicatewiththehostprocessor.
Itindicatesvariouschargeroperations:LOWwhenchargeinprogress.
HIGHwhenchargeiscompleteorinSLEEPmode.
Blinkingat0.
5Hzwhenfaultoccurs,includingchargesuspend,inputover-voltage,timerfaultandbatteryabsent.
10TSITemperaturequalificationvoltageinput.
Connectanegativetemperaturecoefficientthermistor.
ProgramthehotandcoldtemperaturewindowwitharesistordividerfromVREFtoTStoAGND.
The103ATthermistorisrecommended.
11TTCISafetyTimerandterminationcontrol.
ConnectacapacitorfromthisnodetoAGNDtosetthefastchargesafetytimer(5.
6min/nF).
Pre-chargetimerisinternallyfixedto30minutes.
PulltheTTCtoLOWtodisablethechargeterminationandsafetytimer.
PulltheTTCtoHIGHtodisablethesafetytimerbutallowthechargetermination.
12VREFP3.
3Vreferencevoltageoutput.
Placea1-μFceramiccapacitorfromVREFtoAGNDpinclosetotheIC.
ThisvoltagecouldbeusedforprogrammingISETandACSETandTSpins.
13ISETIFastchargecurrentsetpoint.
UseavoltagedividerfromVREFtoISETtoAGNDtosetthefastchargecurrent:Thepre-chargeandterminationcurrentisinternallyasonetenthofthechargecurrent.
ThechargerisdisabledwhenISETpinvoltageisbelow40mVandenabledwhenISETpinvoltageisabove120mV.
14FBIChargevoltageanalogfeedbackadjustment.
ConnecttheoutputofaresistordividerpoweredfromthebatteryterminalstoFBtoAGND.
Outputvoltageisregulatedto2.
1VonFBpinduringconstant-voltagemode.
15SRNIChargecurrentsenseresistornegativeinput.
A0.
1-μFceramiccapacitorisplacedfromSRNtoSRPtoprovidedifferential-modefiltering.
A0.
1-μFceramiccapacitorisplacedfromSRNpintoAGNDforcommon-modefiltering.
16SRPI/PChargecurrentsenseresistor,positiveinput.
A0.
1-μFceramiccapacitorisplacedfromSRNtoSRPtoprovidedifferential-modefiltering.
A0.
1-μFceramiccapacitorisplacedfromSRPpintoAGNDforcommon-modefiltering.
17ACSETIInputcurrentsetpoint.
UseavoltagedividerfromVREFtoACSETtoAGNDtosetthisvalue:18OVPSETIValidinputvoltagesetpoint.
UseavoltagedividerfrominputtoOVPSETtoAGNDtosetthisvoltage.
Thevoltageaboveinternal1.
6Vreferenceindicatesinputover-voltage,andthevoltagebelowinternal0.
5Vreferenceindicatesinputunder-voltage.
Ineithercondition,chargeterminates,andinputNMOSpairACFET/RBFETturnoff.
LEDdrivenbySTATpinkeepsblinking,reportingfaultcondition.
19BATDRVOBatterydischargeMOSFETgatedriveroutput.
Connectto1kohmresistortothegateoftheBATFETP-channelpowerMOSFET.
ConnectthesourceoftheBATFETtothesystemloadvoltagenode.
ConnectthedrainoftheBATFETtothebatterypackpositivenode.
Theinternalgatedriveisasymmetricaltoallowaquickturn-offandslowerturn-on,inadditiontotheinternalbreak-before-makelogicwithrespecttoACDRV.
20REGNPPWMlowsidedriverpositive6Vsupplyoutput.
Connecta1-μFceramiccapacitorfromREGNtoPGNDpin,closetotheIC.
Generatehigh-sidedriverbootstrapvoltagebyintegrateddiodefromREGNtoBTST.
21BTSTPPWMhighsidedriverpositivesupply.
Connectthe0.
047-FbootstrapcapacitorfromSWtoBTST.
22,23PGNDPPowerground.
Groundconnectionforhigh-currentpowerconverternode.
OnPCBlayout,connectdirectlytogroundconnectionofinputandoutputcapacitorsofthecharger.
OnlyconnecttoAGNDthroughtheThermalPadunderneaththeIC.
ThermalAGNDPExposedpadbeneaththeIC.
AlwayssolderThermalPadtotheboard,andhaveviasontheThermalPadPadplanestar-connectingtoAGNDandgroundplaneforhigh-currentpowerconverter.
ItdissipatestheheatfromtheIC.
Copyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback3ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comTYPICALAPPLICATIONSFigure1.
TypicalApplicationSchematic(12Vinput,2cellbattery8.
4V,2Achargecurrent,0.
2Apre-charge/terminationcurrent,3ADPMcurrent,18VinputOVP)4SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013Figure2.
TypicalApplicationSchematicwithSingleCellUnremovableBattery(USBwithinputOVP8V,selectablechargecurrentlimitof900mAor500mA,systemconnectedaftersenseresistor)ORDERINGINFORMATION(1)PARTNUMBERPARTMARKINGPACKAGEORDERINGNUMBERQUANTITYbq24171RGYR3000bq24171bq2417124-Pin3.
5mm*5.
5mmQFNbq24171RGYT250(1)Forthemostcurrentpackageandorderinginformation,seethePackageOptionAddendumattheendofthisdocument,orseetheTIwebsiteatwww.
ti.
com.
Copyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback5ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comABSOLUTEMAXIMUMRATINGSoveroperatingfree-airtemperaturerange(unlessotherwisenoted)(1)(2)VALUEUNITAVCC,ACP,ACN,ACDRV,CMSRC,STAT–0.
3to30PVCC–0.
3to20BATDRV,SRP,SRN–0.
3to20SW–2to20Voltagerange(withrespecttoAGND)VFB–0.
3to16OVPSET,REGN,TS,TTC–0.
3to7VREF,ISET,ACSET–0.
3to3.
6PGND–0.
3to0.
3MaximumdifferencevoltageSRP–SRN,ACP-ACN–0.
5to0.
5VJunctiontemperaturerange,TJ–40to155°CStoragetemperaturerange,Tstg–55to155°C(1)Stressesbeyondthoselistedunderabsolutemaximumratingsmaycausepermanentdamagetothedevice.
Thesearestressratingsonly,andfunctionaloperationofthedeviceattheseoranyotherconditionsbeyondthoseindicatedunderrecommendedoperatingconditionsisnotimplied.
Exposuretoabsolute-maximum-ratedconditionsforextendedperiodsmayaffectdevicereliability.
(2)AllvoltagesarewithrespecttoGNDifnotspecified.
Currentsarepositiveinto,negativeoutofthespecifiedterminal.
ConsultPackagingSectionofthedatabookforthermallimitationsandconsiderationsofpackages.
THERMALINFORMATIONbq24171THERMALMETRIC(1)RGYUNITS24PINSθJAJunction-to-ambientthermalresistance(2)35.
7ψJTJunction-to-topcharacterizationparameter(3)0.
4°C/WψJBJunction-to-boardcharacterizationparameter(4)31.
2(1)Formoreinformationabouttraditionalandnewthermalmetrics,seetheICPackageThermalMetricsapplicationreport,SPRA953.
(2)Thejunction-to-ambientthermalresistanceundernaturalconvectionisobtainedinasimulationonaJEDEC-standard,high-Kboard,asspecifiedinJESD51-7,inanenvironmentdescribedinJESD51-2a.
(3)Thejunction-to-topcharacterizationparameter,ψJT,estimatesthejunctiontemperatureofadeviceinarealsystemandisextractedfromthesimulationdataforobtainingθJA,usingaproceduredescribedinJESD51-2a(sections6and7).
(4)Thejunction-to-boardcharacterizationparameter,ψJB,estimatesthejunctiontemperatureofadeviceinarealsystemandisextractedfromthesimulationdataforobtainingθJA,usingaproceduredescribedinJESD51-2a(sections6and7).
RECOMMENDEDOPERATINGCONDITIONSMINMAXUNITInputvoltageVIN4.
517VOutputvoltageVOUT13.
5VOutputcurrent(RSR10mΩ)IOUT0.
64AACP-ACN–200200mVMaximumdifferencevoltageSRP–SRN–200200mVOperationfree-airtemperaturerange,TA–4085°C6SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013ELECTRICALCHARACTERISTICS4.
5V≤V(PVCC,AVCC)≤17V,–40°CVUVLO,VSRN>VAVCC(SLEEP),15TJ=0°Cto85°CBTST,SW,SRP,SRN,VAVCC>VUVLO,VAVCC>Batterydischargecurrent(sumofcurrentsIBATAVSRN,ISETVUVLO,VAVCC>25VSRN,ISET>120mV,VBAT=12.
6V,ChargedoneVAVCC>VUVLO,VAVCC>VSRN,ISETVUVLO,VAVCC>VSRN,ISET>120mV,IAC2.
55mAAVCC,ACP,ACN)Chargeenabled,noswitchingVAVCC>VUVLO,VAVCC>VSRN,ISET>120mV,15(1)Chargeenabled,switchingCHARGEVOLTAGEREGULATIONVT3VRECHandICHG120mV,Charging120°CTHERMALSHUTDOWNCOMPARATORTSHUTThermalshutdownrisingtemperatureTemperaturerising150°CTSHUT_HYSThermalshutdownhysteresisTemperaturefalling20°CtSHUT_RISE_DEGThermalshutdownrisingdeglitchTemperaturerising100stSHUT_FALL_DEGThermalshutdownfallingdeglitchTemperaturefalling10msTHERMISTORCOMPARATORT1(0°C)threshold,ChargesuspendedVT1VTSrising,AsPercentagetoVVREF70.
2%70.
8%71.
4%belowthistemperature.
ChargebacktoICHARGE/2andVFB=2.
1VVT1-HYSHysteresis,VTSfalling0.
6%abovethistemperature.
T2(10°C)threshold,ChargebacktoVT2ICHARGE/2andVFB=2.
1VbelowthisVTSrising,AsPercentagetoVVREF68.
0%68.
6%69.
2%temperature.
ChargebacktoICHARGEandVFB=2.
1VVT2-HYSHysteresis,VTSfalling0.
8%abovethistemperature.
T3(45°C)threshold,ChargebacktoVT3ICHARGEandVFB=2.
05VabovethisVTSfalling,AsPercentagetoVVREF55.
5%56.
1%56.
7%temperature.
ChargebacktoICHARGEandVFB=2.
1VVT3-HYSHysteresis,VTSrising0.
8%belowthistemperature.
T4(50°C)threshold,ChargebacktoVT4ICHARGEandVFB=2.
025VabovethisVTSfalling,AsPercentagetoVVREF53.
2%53.
7%54.
2%temperature.
ChargebacktoICHARGEandVFB=2.
05VVT4-HYSHysteresis,VTSrising0.
8%belowthistemperature.
T5(60°C)threshold,ChargesuspendedVT5VTSfalling,AsPercentagetoVVREF47.
6%48.
1%48.
6%abovethistemperature.
ChargebacktoICHARGEandVFB=2.
025VVT5-HYSHysteresis,VTSrising1.
2%belowthistemperature.
DeglitchtimeforTemperatureOutofValidVTSVT1400msChargeRangeDetectionDeglitchtimeforTemperatureInValidVTS>VT5+VT5_HYSorVTS2.
2VVOCP_MINChargeOver-CurrentLimitMin,VSRP2.
2VMeasureVSRP-SRN75mVHSFETOVER-CURRENTCOMPARATOR(CYCLE-BY-CYCLE)IOCP_HSFETCurrentlimitonHSFETMeasureonHSFET811.
5ACHARGEUNDER-CURRENTCOMPARATOR(CYCLE-BY-CYCLE)VUCPChargeunder-currentfallingthresholdMeasureonV(SRP-SRN)159mVBATSHORTCOMPARATORVBATSHTBatteryshortfallingthresholdMeasureonSRN2VVBATSHT_HYSBatteryshortrisinghysteresisMeasureonSRN200mVtBATSHT_DEGDeglitchonbothedges1sVBATSHTChargeCurrentduringBATSHORTPercentageoffastchargecurrent10%(4)VREFREGULATORVVREF_REGVREFregulatorvoltageVAVCC>VUVLO,Noload3.
2673.
33.
333VIVREF_LIMVREFcurrentlimitVVREF=0V,VAVCC>VUVLO3590mAREGNREGULATORVREGN_REGREGNregulatorvoltageVAVCC>10V,ISET>120mV5.
76.
06.
3VIREGN_LIMREGNcurrentlimitVREGN=0V,VAVCC>10v,ISET>120mV40120mATTCINPUTtprechrgPrechargeSafetyTimerPrechargetimebeforefaultoccurs162018001980SectfastchrgFastChargeTimerRangeTchg=CTTC*KTTC110hrFastChargeTimerAccuracy-10%10%KTTCTimerMultiplier5.
6min/nFVTTC_LOWTTCLowThresholdTTCfalling0.
4VITTCTTCSource/SinkCurrent455055AVTTC_OSC_HITTCoscillatorhighthreshold1.
5VVTTC_OSC_LOTTCoscillatorlowthreshold1VBATTERYSWITCH(BATFET)DRIVERRDS_BAT_OFFBATFETTurn-offResistanceVAVCC>5V100ΩRDS_BAT_ONBATFETTurn-onResistanceVAVCC>5V20kΩVBATDRV_REG=VACN-VBATDRVwhenVAVCC>5VVBATDRV_REGBATFETDriveVoltage4.
27VandBATFETisonBATFETPower-upDelaytoturnofftBATFET_DEG30msBATFETafteradapterisdetectedACSWITCH(ACFET)DRIVERIACFETACDRVChargePumpCurrentLimitVACDRV-VCMSRC=5V60AVACDRV_REGGateDriveVoltageonACFETVACDRV-VCMSRCwhenVAVCC>VUVLO4.
26VMaximumloadbetweenACDRVandRACDRV_LOAD500kΩCMSRCAC/BATSWITCHDRIVERTIMINGDeadTimewhenswitchingbetweenACFETandtDRV_DEADDriverDeadTime10sBATFET(4)Theminimumcurrentis120mAon10mΩsenseresistor.
10SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013ELECTRICALCHARACTERISTICS(continued)4.
5V≤V(PVCC,AVCC)≤17V,–40°C6VINTERNALSOFTSTART(8stepstoregulationcurrentICHG)SS_STEPSoftstartsteps8stepTSS_STEPSoftstartsteptime1.
63msCHARGERSECTIONPOWER-UPSEQUENCINGDelayfromISETabove120mVtostarttCE_DELAY1.
5schargingbatteryINTEGRATEDBTSTDIODEVFForwardBiasVoltageIF=120mAat25°C0.
85VVRReversebreakdownvoltageIR=2uAat25°C20VLOGICIOPINCHARACTERISTICSVOUT_LOSTATOutputLowSaturationVoltageSinkCurrent=5mA0.
5V(5)SpecifiedbydesignCopyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback11ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comTYPICALCHARACTERISTICSTable1.
TableofGraphs(1)FIGUREDESCRIPTIONFigure3AVCC,VREF,ACDRVandSTATPowerUp(ISET=0)Figure4ChargeEnablebyISETFigure5CurrentSoftStartFigure6ChargeDisablebyISETFigure7ContinuousConductionModeSwitchingFigure8DiscontinuousConductionModeSwitchingFigure9BATFETtoACFETTransitionduringPowerUpFigure10SystemLoadTransient(InputCurrentDPM)Figure11BatteryInsertionandRemovalFigure12BatterytoGroundShortProtectionFigure13BatterytoGroundShortTransitionFigure14EfficiencyvsOutputCurrent(VIN=15V)Figure15EfficiencyvsOutputCurrent(VOUT=3.
8V)(1)AllwaveformsanddataaremeasuredonHPA610andHPA706EVMs.
Figure3.
PowerUp(ISET=0)Figure4.
ChargeEnablebyISETFigure5.
CurrentSoftStartFigure6.
ChargeDisablebyISET12SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013Figure7.
ContinuousConductionModeSwitchingFigure8.
DiscontinuousConductionModeSwitchingFigure9.
BATFETtoACFETTransitionDuringPowerupFigure10.
SystemLoadTransient(InputcurrentDPM)Figure11.
BatteryInsertionandRemovalFigure12.
BatterytoGroundShortProtectionCopyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback13ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comFigure13.
BatterytoGroundShortTransitionFigure14.
EfficiencyvsOutputCurrent(VIN=15V)Figure15.
EfficiencyvsOutputCurrent(VOUT=3.
8V)14SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013FUNCTIONALBLOCKDIAGRAMFigure16.
FunctionalBlockDiagramCopyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback15ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comDETAILEDDESCRIPTIONFigure17.
TypicalChargingProfileBATTERYVOLTAGEREGULATIONThebq24171offersahighaccuracyvoltageregulatoronforthechargingvoltage.
Thebq24171usesexternalresistordividerforvoltagefeedbackandregulatetointernal2.
1VvoltagereferenceonFBpin.
Usethefollowingequationfortheregulationvoltageforbq24171:(1)whereR2isconnectedfromFBtothebatteryandR1isconnectedfromFBtoGND.
BATTERYCURRENTREGULATIONTheISETinputsetsthemaximumchargingcurrent.
BatterycurrentissensedbycurrentsensingresistorRSRconnectedbetweenSRPandSRN.
Thefull-scaledifferentialvoltagebetweenSRPandSRNis40mVmax.
Theequationforchargecurrentis:(2)ThevalidinputvoltagerangeofISETisupto0.
8V.
With10mΩsenseresistor,themaximumoutputcurrentis4A.
With20mΩsenseresistor,themaximumoutputcurrentis2A.
ThechargerisdisabledwhenISETpinvoltageisbelow40mVandisenabledwhenISETpinvoltageisabove120mV.
For10mΩcurrentsensingresistor,theminimumfastchargecurrentmustbehigherthan600mA.
Underhighambienttemperature,thechargecurrentwillfoldbacktokeepICtemperaturenotexceeding120°C.
16SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013BATTERYPRECHARGECURRENTREGULATIONOnPower-up,ifthebatteryvoltageisbelowtheVLOWVthreshold,thebq24171appliesthepre-chargecurrenttothebattery.
Thispre-chargefeatureisintendedtorevivedeeplydischargedcells.
IftheVLOWVthresholdisnotreachedwithin30minutesofinitiatingpre-charge,thechargerturnsoffandaFAULTisindicatedonthestatuspins.
Forbq24171,thepre-chargecurrentissetas10%ofthefastchargeratesetbyISETvoltage.
(3)INPUTCURRENTREGULATIONThetotalinputcurrentfromanACadapterorotherDCsourcesisafunctionofthesystemsupplycurrentandthebatterychargingcurrent.
Systemcurrentnormallyfluctuatedasportionsofthesystemsarepoweredupordown.
WithoutDynamicPowerManagement(DPM),thesourcemustbeabletosupplythemaximumsystemcurrentandthemaximumavailablechargerinputcurrentsimultaneously.
ByusingDPM,theinputcurrentregulatorreducesthechargingcurrentwhenthesummationofsystempowerandchargepowerexceedsthemaximuminputpower.
Therefore,thecurrentcapabilityoftheACadaptercanbelowered,reducingsystemcost.
InputcurrentissetbythevoltageonACSETpinusingthefollowingequation:(4)TheACPandACNpinsareusedtosenseacrossRACwithdefaultvalueof10mΩ.
However,resistorsofothervaluescanalsobeused.
Alargersenseresistorwillgivealargersensevoltageandhigherregulationaccuracy,attheexpenseofhigherconductionloss.
CHARGETERMINATION,RECHARGE,ANDSAFETYTIMERSThechargermonitorsthechargingcurrentduringthevoltageregulationphase.
TerminationisdetectedwhentheFBvoltageishigherthanrechargethresholdandthechargecurrentislessthantheterminationcurrentthreshold,ascalculatedbelow:(5)whereVISETisthevoltageontheISETpinandRSRisthesenseresistor.
Thereisa25msdeglitchtimeduringtransitionbetweenfast-chargeandpre-charge.
Asasafetybackup,thechargeralsoprovidesaninternalfixed30minutespre-chargesafetytimerandaprogrammablefastchargetimer.
ThefastchargetimeisprogrammedbythecapacitorconnectedbetweentheTTCpinandAGND,andisgivenbytheformula:(6)WhereCTTCisthecapacitorconnectedtoTTCandKTTCistheconstantmultiplier.
Anewchargecycleisinitiatedwhenoneofthefollowingconditionsoccurs:ThebatteryvoltagefallsbelowtherechargethresholdApower-on-reset(POR)eventoccursISETpintoggledbelow40mV(disablecharge)andabove120mV(enablecharge)PullTTCpintoAGNDtodisablebothterminationandfastchargesafetytimer(resettimer).
PullTTCpintoVREFtodisablethesafetytimer,butallowchargetermination.
Copyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback17ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comPOWERUPThechargeusesaSLEEPcomparatortodeterminethesourceofpowerontheAVCCpin,sinceAVCCcanbesuppliedeitherfromthebatteryortheadapter.
Withtheadaptersourcepresent,iftheAVCCvoltageisgreaterthantheSRNvoltage,thechargerexitsSLEEPmode.
Ifallconditionsaremetforcharging,thechargerthenstartschargethebattery(seetheEnablingandDisablingChargingsection).
IfSRNvoltageisgreaterthanAVCC,thechargerenterslowquiescentcurrentSLEEPmodetominimizecurrentdrainfromthebattery.
DuringSLEEPmode,theVREFoutputturnsoffandtheSTATpingoestohighimpedance.
IfAVCCisbelowtheUVLOthreshold,thedeviceisdisabled.
INPUTUNDER-VOLTAGELOCK-OUT(UVLO)ThesystemmusthaveaminimumAVCCvoltagetoallowproperoperation.
ThisAVCCvoltagecouldcomefromeitherinputadapterorbattery,sinceaconductionpathexistsfromthebatterytoAVCCthroughthehighsideNMOSbodydiode.
WhenAVCCisbelowtheUVLOthreshold,allcircuitsontheICaredisabled.
INPUTOVER-VOLTAGE/UNDER-VOLTAGEPROTECTIONACOVprovidesprotectiontopreventsystemdamageduetohighinputvoltage.
Inbq24171,oncethevoltageonOVPSETisabovethe1.
6VACOVthresholdorbelowthe0.
5VACUVthreshold,chargeisdisabledandinputMOSFETsturnoff.
Thebq24171providesflexibilitytosettheinputqualificationthreshold.
ENABLEANDDISABLECHARGINGThefollowingconditionshavetobevalidbeforechargingisenabled:ISETpinabove120mVDeviceisnotinUnder-Voltage-Lock-Out(UVLO)mode(i.
e.
VAVCC>VUVLO)DeviceisnotinSLEEPmode(i.
e.
VAVCC>VSRN)OVPSETvoltageisbetween0.
5Vand1.
6Vtoqualifytheadapter1.
5sdelayiscompleteafterinitialpower-upREGNLDOandVREFLDOvoltagesareatcorrectlevelsThermalShutdown(TSHUT)isnotvalidTSfaultisnotdetectedACFETturnson(SeeSystemPowerSelectorfordetails)Oneofthefollowingconditionsstopson-goingcharging:ISETpinvoltageisbelow40mVDeviceisinUVLOmodeAdapterisremoved,causingthedevicetoenterSLEEPmodeOVPSETvoltageindicatestheadapterisnotvalidREGNorVREFLDOvoltageisoverloadedTSHUTtemperaturethresholdisreachedTSvoltagegoesoutofrangeindicatingthebatterytemperatureistoohotortoocoldACFETturnsoffTTCtimerexpiresorpre-chargetimerexpiresSYSTEMPOWERSELECTORTheICautomaticallyswitchesadapterorbatterypowertothesystemload.
ThebatteryisconnectedtothesystembydefaultduringpoweruporduringSLEEPmode.
Whentheadapterplugsinandthevoltageisabovethebatteryvoltage,theICexitsSLEEPmode.
ThebatteryisdisconnectedfromthesystemandtheadapterisconnectedtothesystemafterexitingSLEEP.
Anautomaticbreak-before-makelogicpreventsshoot-throughcurrentswhentheselectorsswitch.
18SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013TheACDRVisusedtodriveapairofback-to-backn-channelpowerMOSFETsbetweenadapterandACPwithsourcesconnectedtogethertoCMSRC.
Then-channelFETwiththedrainconnectedtotheACP(Q2,RBFET)providesreversebatterydischargeprotection,andminimizessystempowerdissipationwithitslow-RDSON.
Theothern-channelFETwithdrainconnectedtoadapterinput(Q1,ACFET)separatesbatteryfromadapter,andprovidesalimiteddI/dtwhenconnectingtheadaptertothesystembycontrollingtheFETturn-ontime.
The/BATDRVcontrolsap-channelpowerMOSFET(Q3,BATFET)placedbetweenbatteryandsystemwithdrainconnectedtobattery.
Beforetheadapterisdetected,theACDRVispulledtoCMSRCtokeepACFEToff,disconnectingtheadapterfromsystem.
/BATDRVstaysatACN-6V(clamptoground)toconnectbatterytosystemifallthefollowingconditionsarevalid:VAVCC>VUVLO(batterysuppliesAVCC)VACNVSRN+300mVWhentheadapterisremoved,theICturnsoffACFETandentersSLEEPmode.
BATFETkeepsoffuntilthesystemdropsclosetoSRN.
TheBATDRVpinisdriventoACN-6Vbyaninternalregulatortoturnonp-channelBATFET,connectingthebatterytothesystem.
Asymmetricalgatedriveprovidesfastturn-offandslowturn-onoftheACFETandBATFETtohelpthebreak-before-makelogicandtoallowasoft-startatturn–onofbothMOSFETs.
Thedelaytimecanbefurtherincreased,byputtingacapacitorfromgatetosourceofthepowerMOSFETs.
CONVERTEROPERATIONThebq24171employsa1.
6MHzconstant-frequencystep-downswitchingregulator.
Thefixedfrequencyoscillatorkeepstightcontroloftheswitchingfrequencyunderallconditionsofinputvoltage,batteryvoltage,chargecurrent,andtemperature,simplifyingoutputfilterdesignandkeepingitoutoftheaudiblenoiseregion.
AtypeIIIcompensationnetworkallowsusingceramiccapacitorsattheoutputoftheconverter.
Aninternalsaw-toothrampiscomparedtotheinternalerrorcontrolsignaltovarytheduty-cycleoftheconverter.
TherampheightisproportionaltotheAVCCvoltagetocanceloutanyloopgainvariationduetoachangeininputvoltage,andsimplifiestheloopcompensation.
Internalgatedrivelogicallowsachieving97%duty-cyclebeforepulseskippingstarts.
AUTOMATICINTERNALSOFT-STARTCHARGERCURRENTThechargerautomaticallysoft-startsthechargerregulationcurrenteverytimethechargergoesintofast-chargetoensurethereisnoovershootorstressontheoutputcapacitorsorthepowerconverter.
Thesoft-startconsistsofstepping-upthechargeregulationcurrentinto8evenlydividedstepsuptotheprogrammedchargecurrent.
Eachsteplastsaround1.
6ms,foratypicalrisetimeof12.
8ms.
Noexternalcomponentsareneededforthisfunction.
CHARGEOVER-CURRENTPROTECTIONThechargermonitorstopsideMOSFETcurrentbyhighsidesenseFET.
WhenpeakcurrentexceedsMOSFETlimit,itwillturnoffthetopsideMOSFETandkeepitoffuntilthenextcycle.
Thechargerhasasecondarycycle-to-cycleover-currentprotection.
Itmonitorsthechargecurrent,andpreventsthecurrentfromexceeding160%oftheprogrammedchargecurrent.
Thehigh-sidegatedriveturnsoffwheneitherover-currentconditionisdetected,andautomaticallyresumeswhenthecurrentfallsbelowtheover-currentthreshold.
Copyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback19ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
ti.
comCHARGEUNDER-CURRENTPROTECTIONAftertherecharge,iftheSRP-SRNvoltagedecreasesbelow5mV,thelowsideFETwillbeturnedofffortherestoftheswitchingcycle.
Duringdiscontinuousconductionmode(DCM),thelowsideFETwillonlyturnonforashortperiodoftimewhenthebootstrapcapacitorvoltagedropsbelow4Vtoproviderefreshchargeforthecapacitor.
Thisisimportanttopreventnegativeinductorcurrentfromcausinganyboosteffectinwhichtheinputvoltageincreasesaspoweristransferredfromthebatterytotheinputcapacitors.
Thiscanleadtoanover-voltageontheAVCCnodeandpotentiallycausedamagetothesystem.
BATTERYDETECTIONForapplicationswithremovablebatterypacks,ICprovidesabatteryabsentdetectionschemetoreliablydetectinsertionorremovalofbatterypacks.
Thebatterydetectionroutinerunsonpowerup,orifbatteryvoltagefallsbelowrechargethresholdvoltageduetoremovingabatteryordischargingabattery.
Figure18.
BatteryDetectionFlowchart20SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013Oncethedevicehaspoweredup,a8-mAdischargecurrentisappliedtotheSRNterminal.
IfthebatteryvoltagefallsbelowtheLOWVthresholdwithin1second,thedischargesourceisturnedoff,andthechargeristurnedonatlowchargecurrent(125mA).
Ifthebatteryvoltagegetsupabovetherechargethresholdwithin500ms,thereisnobatterypresentandthecyclerestarts.
Ifeitherthe500msor1secondtimertimeoutbeforetherespectivethresholdsarehit,abatteryisdetectedandachargecycleisinitiated.
Figure19.
BatteryDetectTimingDiagramCaremustbetakenthatthetotaloutputcapacitanceatthebatterynodeisnotsolargethatthedischargecurrentsourcecannotpullthevoltagebelowtheLOWVthresholdduringthe1seconddischargetime.
Themaximumoutputcapacitancescanbecalculatedaccordingtothefollowingequation:(7)WhereCMAXisthemaximumoutputcapacitance,IDISCHisthedischargecurrent,tDISCHisthedischargetime,andR2andR1arethevoltagefeedbackresistorsfromthebatterytotheFBpin.
ExampleFora3-cellLi+charger,withR2=500kΩ,R1=100kΩ(giving12.
6Vforvoltageregulation),IDISCH=8mA,tDISCH=1second.
(8)Basedonthesecalculations,nomorethan2200Fshouldbeallowedonthebatterynodeforproperoperationofthebatterydetectioncircuit.
BATTERYSHORTPROTECTIONWhenSRNpinvoltageislowerthan2Vitisconsideredasbatteryshortconditionduringchargingperiod.
Thechargerwillshutdownimmediatelyfor1ms,thensoftstartbacktothechargingcurrentthesameasprechargecurrent.
Thispreventshighcurrentmaybuildinoutputinductorandcauseinductorsaturationwhenbatteryterminalisshortedduringcharging.
Theconverterworksinnon-synchronousmodeduringbatteryshort.
BATTERYOVER-VOLTAGEPROTECTIONTheconverterwillnotallowthehigh-sideFETtoturn-onuntilthebatteryvoltagegoesbelow102%oftheregulationvoltage.
Thisallowsone-cycleresponsetoanover-voltagecondition–suchasoccurswhentheloadisremovedorthebatteryisdisconnected.
Atotal6mAcurrentsinkfromSRP/SRNtoAGNDallowsdischargingthestoredoutputinductorenergythatistransferredtotheoutputcapacitors.
Ifbatteryover-voltageconditionlastsformorethan30ms,chargeisdisabled.
Copyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback21ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
ti.
comTEMPERATUREQUALIFICATIONANDJEITAGUIDELINEThecontrollercontinuouslymonitorsbatterytemperaturebymeasuringthevoltagebetweentheTSpinandGND.
Anegativetemperaturecoefficientthermistor(NTC)andanexternalvoltagedividertypicallydevelopthisvoltage.
Thecontrollercomparesthisvoltageagainstitsinternalthresholdstodetermineifchargingisallowed.
Toinitiateachargecycle,thevoltageonTSpinmustbewithintheVT1toVT5thresholds.
IfVTSisoutsideofthisrange,thecontrollersuspendschargeandwaitsuntilthebatterytemperatureiswithintheVT1toVT5range.
DuringthechargecyclethebatterytemperaturemustbewithintheVT1toVT5thresholds.
Ifbatterytemperatureisoutsideofthisrange,thecontrollersuspendschargeandwaitsuntilthebatterytemperatureiswithintheVT1toVT5range.
ThecontrollersuspendschargebyturningoffthePWMchargeFETs.
IfVTSiswithintherangeofVT1andVT2,chargevoltageregulationonFBpinis2.
1VandthechargecurrentisreducedtoICHARGE/2(ToavoidearlyterminationduringVT1andVT2range,fastchargecurrentneedtobebiggerthan2timesofterminationcurrent);ifVTSiswithintherangeofVT2andVT3,thechargevoltageregulationonFBpinis2.
1V;ifVTSiswithinVT3andVT4,thechargevoltageregulationonFBpinisreducedbackto2.
05V;andifVTSiswithinVT4andVT5,thechargevoltageregulationonFBpinisfurtherreducedto2.
025V.
Figure20belowsummarizestheoperation.
SeetheLi-ionbattery-chargersolutionsforJEITAcompliance,SLYT365Figure20.
TSPin,ThermistorSenseThresholdsAssuminga103ATNTCthermistoronthebatterypackasshowninFigure21,thevaluesofRT1andRT2canbedeterminedbyusingEquation9andEquation10:(9)(10)22SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013Figure21.
TSResistorNetworkForexample,103ATNTCthermistorsareusedtomonitorthebatterypacktemperature.
SelectT1=0CforCOLDandT5=60CforHOT,thenwegetRT2=6.
8kΩandRT1=2.
2kΩasinthedesigntool.
AsmallRCfilterissuggestedtouseforsystem-levelESDprotection.
MOSFETSHORTCIRCUITANDINDUCTORSHORTCIRCUITPROTECTIONTheIChasashortcircuitprotectionfeature.
Itscycle-by-cyclecurrentmonitoringfeatureisachievedthroughmonitoringthevoltagedropacrossRdsonoftheMOSFETs.
Thechargerwillbelatchedoff,buttheACFETkeepontopowerthesystem.
Theonlywaytoresetthechargerfromlatch-offstatusisremoveadapterthenplugadapterinagain.
Meanwhile,STATisblinkingtoreportthefaultcondition.
THERMALREGULATIONANDSHUTDOWNPROTECTIONTheQFNpackagehaslowthermalimpedance,whichprovidesgoodthermalconductionfromthesilicontotheambient,tokeepjunctionstemperatureslow.
Theinternalthermalregulationloopwillfoldbackthechargecurrenttokeepthejunctiontemperaturefromexceeding120°C.
Asaddedlevelofprotection,thechargerconverterturnsoffandself-protectswheneverthejunctiontemperatureexceedstheTSHUTthresholdof150°C.
Thechargerstaysoffuntilthejunctiontemperaturefallsbelow130°C.
TIMERFAULTRECOVERYTheICprovidesarecoverymethodtodealwithtimerfaultconditions.
Thefollowingsummarizesthismethod:Condition1:Thebatteryvoltageisabovetherechargethresholdandatimeoutfaultoccurs.
RecoveryMethod:Thetimerfaultwillclearwhenthebatteryvoltagefallsbelowtherechargethreshold,andbatterydetectionwillbegin.
APORortakingISETbelow40mVwillalsoclearthefault.
Condition2:Thebatteryvoltageisbelowtherechargethresholdandatimeoutfaultoccurs.
RecoveryMethod:Underthisscenario,theICappliesthefaultcurrenttothebattery.
Thissmallcurrentisusedtodetectabatteryremovalconditionandremainsonaslongasthebatteryvoltagestaysbelowtherechargethreshold.
Ifthebatteryvoltagegoesabovetherechargethreshold,theICdisabledthefaultcurrentandexecutestherecoverymethoddescribedinCondition1.
APORortakingISETbelow40mVwillalsoclearthefault.
INDUCTOR,CAPACITOR,ANDSENSERESISTORSELECTIONGUIDELINESTheICprovidesinternalloopcompensation.
Withthisscheme,thebeststabilityoccurswhentheLCresonantfrequency,fo,isapproximately15kHz–25kHzfortheIC.
(11)Copyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback23ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comTable2providesasummaryoftypicalLCcomponentsforvariouschargecurrents.
Table2.
TypicalValuesasaFunctionofChargeCurrentCHARGECURRENT1A2A3A4AOutputinductorL6.
8H3.
3H3.
3H2.
2HOutputcapacitorC10F20F20F30FCHARGESTATUSOUTPUTSTheopen-drainSTAToutputsindicatevariouschargeroperationsaslistedinTable3.
ThesestatuspinscanbeusedtodriveLEDsorcommunicatewiththehostprocessor.
NotethatOFFindicatesthattheopen-draintransistoristurnedoff.
Table3.
STATPinDefinitionCHARGESTATESTATChargeinprogress(includingrecharging)ONChargecomplete,Sleepmode,ChargedisabledOFFChargesuspend,Inputover-voltage,Batteryover-voltage,timerfault,,batteryabsentBLINK24SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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comSLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013APPLICATIONINFORMATIONINDUCTORSELECTIONThebq24171hasa1600-kHzswitchingfrequencytoallowtheuseofsmallinductorandcapacitorvalues.
Inductorsaturationcurrentshouldbehigherthanthechargingcurrent(ICHG)plushalftheripplecurrent(IRIPPLE):(12)Inductorripplecurrentdependsoninputvoltage(VIN),dutycycle(D=VOUT/VIN),switchingfrequency(fs),andinductance(L):(13)ThemaximuminductorripplecurrenthappenswithD=0.
5orcloseto0.
5.
Usuallyinductorrippleisdesignedintherangeof20%to40%ofthemaximumchargingcurrentasatrade-offbetweeninductorsizeandefficiencyforapracticaldesign.
INPUTCAPACITORTheinputcapacitorshouldhaveenoughripplecurrentratingtoabsorbinputswitchingripplecurrent.
TheworstcaseRMSripplecurrentishalfofthechargingcurrentwhendutycycleis0.
5.
Iftheconverterdoesnotoperateat50%dutycycle,thentheworstcasecapacitorRMScurrentICINoccurswherethedutycycleisclosestto50%andcanbeestimatedbythefollowingequation:(14)AlowESRceramiccapacitorsuchasX7RorX5Rispreferredfortheinputdecouplingcapacitorandshouldbeplacedascloseaspossibletothedrainofthehigh-sideMOSFETandsourceofthelow-sideMOSFET.
Thevoltageratingofthecapacitormustbehigherthanthenormalinputvoltagelevel.
A25Vratingorhighercapacitorispreferredfora15Vinputvoltage.
A20μFcapacitanceissuggestedforatypical3Ato4Achargingcurrent.
OUTPUTCAPACITORTheoutputcapacitoralsoshouldhaveenoughripplecurrentratingtoabsorboutputswitchingripplecurrent.
TheoutputcapacitorRMScurrentICOUTisgivenas:(15)Theoutputcapacitorvoltageripplecanbecalculatedasfollows:(16)Atcertaininput/outputvoltagesandswitchingfrequencies,thevoltageripplecanbereducedbyincreasingtheoutputfilterLC.
Thebq24171hasaninternalloopcompensator.
Toachievegoodloopstability,theresonantfrequencyoftheoutputinductorandoutputcapacitorshouldbedesignedbetween15kHzand25kHz.
Thepreferredceramiccapacitorhasa25Vorhigherrating,X7RorX5R.
INPUTFILTERDESIGNDuringadapterhotplug-in,theparasiticinductanceandtheinputcapacitorfromtheadaptercableformasecondordersystem.
ThevoltagespikeattheAVCCpinmaybebeyondtheICmaximumvoltageratinganddamagetheIC.
Theinputfiltermustbecarefullydesignedandtestedtopreventanover-voltageeventontheAVCCpin.
Thereareseveralmethodstodampingorlimitingtheover-voltagespikeduringadapterhotplug-in.
AnelectrolyticcapacitorwithhighESRasaninputcapacitorcandamptheover-voltagespikewellbelowtheICmaximumpinvoltagerating.
AhighcurrentcapabilityTVSZenerdiodecanalsolimittheover-voltageleveltoanICsafelevel.
However,thesetwosolutionsmaynotbelowestcostorsmallestsize.
Copyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback25ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
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comAcosteffectiveandsmallsizesolutionisshowninFigure22.
R1andC1arecomposedofadampingRCnetworktodampthehotplug-inoscillation.
Asaresult,theover-voltagespikeislimitedtoasafelevel.
D1isusedforreversevoltageprotectionfortheAVCCpin.
C2istheAVCCpindecouplingcapacitoranditshouldbeplacedascloseaspossibletotheAVCCpin.
R2andC2formadampingRCnetworktofurtherprotecttheICfromhighdv/dtandhighvoltagespikes.
TheC2valueshouldbelessthantheC1valuesoR1candominanttheequivalentESRvaluetoprovideenoughdampingeffectforhotplug-in.
R1andR2mustbesizedtohandlein-rushcurrentpowerlossaccordingtotheresistormanufacturer'sdatasheet.
Verifythefiltercomponentvalueswitharealapplicationandmakeanyminoradjustmentsneededtofitintherealapplicationcircuit.
Iftheinputis5V(USBhostorUSBadapter),diodeD1canbeomitted.
R2mustbe5Ωorhighertolimitthecurrentiftheinputisreverselyinserted.
Figure22.
InputFilterINPUTACFETANDRBFETSELECTIONN-typeMOSFETsareusedasinputACFET(Q1)andRBFET(Q2)forbettercosteffectiveandsmallsizesolution,asshowninFigure23.
Normally,therearearound50uFcapacitortotallyconnectedatPVCCnode---10Fcapacitorforbuckconverterofbq24171and40Fcapacitorforsystemside.
ThereisasurgecurrentduringQ1turn-onperiodwhenavalidadapterisinserted.
Decreasingtheturn-onspeedofQ1canlimitthissurgecurrentindesirablerangebyselectingaMOSFETwithrelativebiggerCGDand/orCGS.
AtthecaseQ1turnontoofast,weneedaddexternalCGDand/orCGS.
Forexample,4.
7nFCGDand47nFCGSareadoptedonEVMwhileusingNexFETCSD17313asQ1.
Figure23.
InputACFETandRBFETPCBLAYOUTTheswitchingnoderiseandfalltimesshouldbeminimizedforminimumswitchingloss.
Properlayoutofthecomponentstominimizethehighfrequencycurrentpathloop(seeFigure24)isimportanttopreventelectricalandmagneticfieldradiationandhighfrequencyresonantproblems.
ThefollowingisaPCBlayoutprioritylistforproperlayout.
LayoutofthePCBaccordingtothisspecificorderisessential.
1.
PlaceinputcapacitorascloseaspossibletothePVCCsupplyandgroundconnectionsandusetheshortestcoppertraceconnection.
ThesepartsshouldbeplacedonthesamelayerofthePCBinsteadofondifferentlayersandusingviastomakethisconnection.
2.
PlacetheinductorinputterminalascloseaspossibletotheSWterminal.
Minimizethecopperareaofthistracetolowerelectricalandmagneticfieldradiationbutmakethetracewideenoughtocarrythechargingcurrent.
Donotusemultiplelayersinparallelforthisconnection.
Minimizeparasiticcapacitancefromthisareatoanyothertraceorplane.
26SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171bq24171www.
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Thechargingcurrentsensingresistorshouldbeplacedrightnexttotheinductoroutput.
RoutethesenseleadsconnectedacrossthesensingresistorbacktotheICinthesamelayer,closetoeachother(minimizelooparea)anddonotroutethesenseleadsthroughahigh-currentpath(seeFigure25forKelvinconnectionforbestcurrentaccuracy).
PlacedecouplingcapacitoronthesetracesnexttotheIC.
4.
Placeoutputcapacitornexttothesensingresistoroutputandground.
5.
Outputcapacitorgroundconnectionsneedtobetiedtothesamecopperthatconnectstotheinputcapacitorgroundbeforeconnectingtosystemground.
6.
Routeanaloggroundseparatelyfrompowergroundanduseasinglegroundconnectiontotiechargerpowergroundtochargeranalogground.
JustbeneaththeICuseanaloggroundcopperpourbutavoidpowerpinstoreduceinductiveandcapacitivenoisecoupling.
Usethethermalpadasasinglegroundconnectionpointtoconnectanaloggroundandpowergroundtogether,orusea0-Ωresistortotieanaloggroundtopowerground.
Astar-connectionunderthethermalpadishighlyrecommended.
7.
ItiscriticalthattheexposedthermalpadonthebacksideoftheICpackagebesolderedtothePCBground.
EnsurethattherearesufficientthermalviasdirectlyundertheIC,connectingtothegroundplaneontheotherlayers.
8.
DecouplingcapacitorsshouldbeplacednexttotheICpinsandmaketraceconnectionasshortaspossible.
9.
Thenumberandphysicalsizeoftheviasshouldbeenoughforagivencurrentpath.
Figure24.
HighFrequencyCurrentPathFigure25.
SensingResistorPCBLayoutCopyright2011–2013,TexasInstrumentsIncorporatedSubmitDocumentationFeedback27ProductFolderLinks:bq24171bq24171SLUSAF2B–FEBRUARY2011–REVISEDOCTOBER2013www.
ti.
comREVISIONHISTORYNote:Pagenumbersofcurrentversionmaydifferfrompreviousversions.
ChangesfromRevisionA(April2011)toRevisionBPageChangedpublicationtoRevB,October20131ChangedFigure2diodeD1symboltoamoredistinctimagetoshowitisaSchottkydiode.
5Changedfigurereferencepointerfrom"Figure22"to"Figure23"inINPUTADFETANDRBDETSELECTIONdecscription.
26ChangedresistornameinFigure23from"Rsns"to"Rac"26ChangesfromOriginal(February2011)toRevisionAPageChangedpublicationtoRevA,May20111Changedthe4thFEATURESbulletfrom"4.
5Vto17VInputOperatingVoltage"to"30VInputRatingwithAdjustableOver-VoltageProtection"andsub-bullet"4.
5Vto17VInputOperatingVoltage"1Addedesdsnotetotopofsecondpage;added"DESCRIPTION(Continued)"titleonsecondpage;andnewparagraphonpage2(beginning"Thebq24171chargesbatteryfromDCsourceashighas17V.
2AddedconnectionbetweenCMSRCandACPinFigure2TypicalApplicationschematic.
5ChangedABSMAXtablefirst-rowdescriptorsfrom"PVCC,AVCC,ACN,CMSRC,STAT"to"AVCC,ACP,ACN,ACDRV,CMSRC,STAT"andsecond-rowdescriptorfrom"ACDRV,BTST"to"PVCC";changedPVCCmaxvoltagefrom30Vto20V6ChangedhyperlinktopointtoDesignToolsluc244a23AddednewparagraphunderINPUTFILTERDESIGNsection(beginning.
.
.
"Iftheinputis5V.
2628SubmitDocumentationFeedbackCopyright2011–2013,TexasInstrumentsIncorporatedProductFolderLinks:bq24171PACKAGEOPTIONADDENDUMwww.
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com11-Apr-2013Addendum-Page1PACKAGINGINFORMATIONOrderableDeviceStatus(1)PackageTypePackageDrawingPinsPackageQtyEcoPlan(2)Lead/BallFinishMSLPeakTemp(3)OpTemp(°C)Top-SideMarkings(4)SamplesBQ24171RGYRACTIVEVQFNRGY243000Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to85BQ24171BQ24171RGYTACTIVEVQFNRGY24250Green(RoHS&noSb/Br)CUNIPDAULevel-2-260C-1YEAR-40to85BQ24171(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)MultipleTop-SideMarkingswillbeinsideparentheses.
OnlyoneTop-SideMarkingcontainedinparenthesesandseparatedbya"~"willappearonadevice.
IfalineisindentedthenitisacontinuationofthepreviouslineandthetwocombinedrepresenttheentireTop-SideMarkingforthatdevice.
ImportantInformationandDisclaimer:TheinformationprovidedonthispagerepresentsTI'sknowledgeandbeliefasofthedatethatitisprovided.
TIbasesitsknowledgeandbeliefoninformationprovidedbythirdparties,andmakesnorepresentationorwarrantyastotheaccuracyofsuchinformation.
Effortsareunderwaytobetterintegrateinformationfromthirdparties.
TIhastakenandcontinuestotakereasonablestepstoproviderepresentativeandaccurateinformationbutmaynothaveconducteddestructivetestingorchemicalanalysisonincomingmaterialsandchemicals.
TIandTIsuppliersconsidercertaininformationtobeproprietary,andthusCASnumbersandotherlimitedinformationmaynotbeavailableforrelease.
InnoeventshallTI'sliabilityarisingoutofsuchinformationexceedthetotalpurchasepriceoftheTIpart(s)atissueinthisdocumentsoldbyTItoCustomeronanannualbasis.
TAPEANDREELINFORMATION*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQReelDiameter(mm)ReelWidthW1(mm)A0(mm)B0(mm)K0(mm)P1(mm)W(mm)Pin1QuadrantBQ24171RGYRVQFNRGY243000330.
012.
43.
85.
81.
28.
012.
0Q1BQ24171RGYTVQFNRGY24250180.
012.
43.
85.
81.
28.
012.
0Q1PACKAGEMATERIALSINFORMATIONwww.
ti.
com14-Jul-2012PackMaterials-Page1*AlldimensionsarenominalDevicePackageTypePackageDrawingPinsSPQLength(mm)Width(mm)Height(mm)BQ24171RGYRVQFNRGY243000367.
0367.
035.
0BQ24171RGYTVQFNRGY24250210.
0185.
035.
0PACKAGEMATERIALSINFORMATIONwww.
ti.
com14-Jul-2012PackMaterials-Page2IMPORTANTNOTICETexasInstrumentsIncorporatedanditssubsidiaries(TI)reservetherighttomakecorrections,enhancements,improvementsandotherchangestoitssemiconductorproductsandservicesperJESD46,latestissue,andtodiscontinueanyproductorserviceperJESD48,latestissue.
Buyersshouldobtainthelatestrelevantinformationbeforeplacingordersandshouldverifythatsuchinformationiscurrentandcomplete.
Allsemiconductorproducts(alsoreferredtohereinas"components")aresoldsubjecttoTI'stermsandconditionsofsalesuppliedatthetimeoforderacknowledgment.
TIwarrantsperformanceofitscomponentstothespecificationsapplicableatthetimeofsale,inaccordancewiththewarrantyinTI'stermsandconditionsofsaleofsemiconductorproducts.
TestingandotherqualitycontroltechniquesareusedtotheextentTIdeemsnecessarytosupportthiswarranty.
Exceptwheremandatedbyapplicablelaw,testingofallparametersofeachcomponentisnotnecessarilyperformed.
TIassumesnoliabilityforapplicationsassistanceorthedesignofBuyers'products.
BuyersareresponsiblefortheirproductsandapplicationsusingTIcomponents.
TominimizetherisksassociatedwithBuyers'productsandapplications,Buyersshouldprovideadequatedesignandoperatingsafeguards.
TIdoesnotwarrantorrepresentthatanylicense,eitherexpressorimplied,isgrantedunderanypatentright,copyright,maskworkright,orotherintellectualpropertyrightrelatingtoanycombination,machine,orprocessinwhichTIcomponentsorservicesareused.
InformationpublishedbyTIregardingthird-partyproductsorservicesdoesnotconstitutealicensetousesuchproductsorservicesorawarrantyorendorsementthereof.
Useofsuchinformationmayrequirealicensefromathirdpartyunderthepatentsorotherintellectualpropertyofthethirdparty,oralicensefromTIunderthepatentsorotherintellectualpropertyofTI.
ReproductionofsignificantportionsofTIinformationinTIdatabooksordatasheetsispermissibleonlyifreproductioniswithoutalterationandisaccompaniedbyallassociatedwarranties,conditions,limitations,andnotices.
TIisnotresponsibleorliableforsuchaltereddocumentation.
Informationofthirdpartiesmaybesubjecttoadditionalrestrictions.
ResaleofTIcomponentsorserviceswithstatementsdifferentfromorbeyondtheparametersstatedbyTIforthatcomponentorservicevoidsallexpressandanyimpliedwarrantiesfortheassociatedTIcomponentorserviceandisanunfairanddeceptivebusinesspractice.
TIisnotresponsibleorliableforanysuchstatements.
Buyeracknowledgesandagreesthatitissolelyresponsibleforcompliancewithalllegal,regulatoryandsafety-relatedrequirementsconcerningitsproducts,andanyuseofTIcomponentsinitsapplications,notwithstandinganyapplications-relatedinformationorsupportthatmaybeprovidedbyTI.
Buyerrepresentsandagreesthatithasallthenecessaryexpertisetocreateandimplementsafeguardswhichanticipatedangerousconsequencesoffailures,monitorfailuresandtheirconsequences,lessenthelikelihoodoffailuresthatmightcauseharmandtakeappropriateremedialactions.
BuyerwillfullyindemnifyTIanditsrepresentativesagainstanydamagesarisingoutoftheuseofanyTIcomponentsinsafety-criticalapplications.
Insomecases,TIcomponentsmaybepromotedspecificallytofacilitatesafety-relatedapplications.
Withsuchcomponents,TI'sgoalistohelpenablecustomerstodesignandcreatetheirownend-productsolutionsthatmeetapplicablefunctionalsafetystandardsandrequirements.
Nonetheless,suchcomponentsaresubjecttotheseterms.
NoTIcomponentsareauthorizedforuseinFDAClassIII(orsimilarlife-criticalmedicalequipment)unlessauthorizedofficersofthepartieshaveexecutedaspecialagreementspecificallygoverningsuchuse.
OnlythoseTIcomponentswhichTIhasspecificallydesignatedasmilitarygradeor"enhancedplastic"aredesignedandintendedforuseinmilitary/aerospaceapplicationsorenvironments.
BuyeracknowledgesandagreesthatanymilitaryoraerospaceuseofTIcomponentswhichhavenotbeensodesignatedissolelyattheBuyer'srisk,andthatBuyerissolelyresponsibleforcompliancewithalllegalandregulatoryrequirementsinconnectionwithsuchuse.
TIhasspecificallydesignatedcertaincomponentsasmeetingISO/TS16949requirements,mainlyforautomotiveuse.
Inanycaseofuseofnon-designatedproducts,TIwillnotberesponsibleforanyfailuretomeetISO/TS16949.
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