www.ti.com Programmable NiCd/NiMH Fast …

1 SEPTEMBER2001 REVISEDMARCH2010 ProgrammableNiCd/NiMHFast-ChargeManageme ntICCheckforSamples:bq244011 FEATURESGENERALDESCRIPTION SafeManagementofFastChargeforNiCdandNiMH BatteryPacksThebq24401isa Programmable ,monolithicICforfast-chargem anagementofnickelcadmium(NiCd) High-FrequencySwitchingControllerforandn ickelmetal-hydride(NiMH)in singleormulti-cellEfficientandSimpleChar gerDesignapplications. Pre-ChargeQualificationforDetectingThebq 24401providesthesechargeterminationShort ed,Damaged,orOverheatedCellscriteria: Fast-ChargeTerminationby T/ t, Maximum Rateoftemperaturerise( T/ t)Temperature,andMaximumChargeTime Maximumtemperature SelectableTop-OffModeforAchieving MaximumchargetimeMaximumCapacityinNiMHBa tteries ProgrammableTrickle-ChargeModeforForsafe ty, thebatteryvoltageis belowthePostchargeMaintenancelow-voltage threshold,thebq24401uses ,thebq24401providesanoptionaltop-off , NickelChargerhigh-efficiencybatterycharg ercircuitfornickel-based High-Power, ,standardwarranty,andusein 2001 2010, SEPTEMBER2001 serieswiththebatterypackVSSS ystemGroundConnecttothebattery s negativeterminalLEDC harge-statusoutputOpen-drainoutputthatin dicatesthechargingstatusbyturningon,turn ingoff,orflashinganexternalLED.

2 Driventhrougha simpleresistivedivider,acrossthebatteryt erminals, ,maximumtop-offcharge-time,hold-offperio d,tricklechargerate, capacitorfromVCCanda 10 F + F F 2001 2010,TexasInstrumentsIncorporatedProduct FolderLink(s):bq24401 VoltageReferenceInternalOSCC lockPhaseGeneratorADCOSCSNSTSMODRCBATLED VCCVSST imerD DT/ tALUV oltageComparators SEPTEMBER2001 REVISEDMARCH2010 FUNCTIONALDESCRIPTIONT hebq24401isa versatile, fora functionalblockdiagramandFigure2 fora 2001 2010,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback3 ProductFolderLink(s) V < V< VCCC hargeInitializationBattery Voltage (Voltage at BAT pinchecked continuously.)

3 SleepModeV< VBATSLPV<MCVV< VBATSLPC hargeQualificationStateV< VBATMCVB attery Temperature(Temperature at TS pin checkedcontinuously. Sampled every 8 secondsfor T/ t.)D DVResetorBattery Replacement at any timeCCChargeSuspendedV> VTSHTFV< VTSHTFB atteryConditioningCurrentRegulationV< VBATLBATorV> VTSLTFV< VTSHTFV> VTSLTFVVV< VLBATBATHTFTSLTF<and< VV< V< VandV< V< VLBATBATMCVHTFTSLTFD DT/ t (after hold-off period),or V< VorTime = MTOTSTCOTop-OffSelected?TrickleMaintenanceChargeNOYESTop-OffV> VTSLTFV< VTSLTFandTime < MTOTime = MTODoneVVBATMCV VVBATMCV ChargeSuspended(See Note)V< VTSHTFV> VTSHTFand Time < MTOV< VTSHTFV> VTSHTFVR eset or Battery ReplacementCCFast Charge StateV<SLPV< VBATCCbq24401 SLUS497A SEPTEMBER2001 :If VTS< VTCO atanytime, 2001 2010,TexasInstrumentsIncorporatedProduct FolderLink(s) SEPTEMBER2001 REVISEDMARCH2010 ABSOLUTEMAXIMUMRATINGS(1)VALUEUNITVCCVCC relativetoVSS ,relativetoVSS 20to70 CTSTGS toragetemperature 40to125 CTSOLDERS olderingtemperature(10s max.)

4 260 C(1)Permanentdevicedamagemayoccurif (1)TA= TOPR; VCC= 5V 20%(unlessotherwisespecified) VCC 5% VCC 5% VCC 5% 5%mVVThermTSinputchangefor T/ t detectionVoltageattheTSpin VCC/161 25%V/minVSNSHIH ighthresholdatSNSV oltageattheSNSpin50 10mVVSNSLOL owthresholdatSNSV oltageattheSNSpin 50 10mVVSLPS leep-modeinputthresholdVoltageattheBATpi nVCC 1 (1) (unlessotherwisenoted) VSLP5 AVTST hermistorinputVTS< ,IOH= 10mAVCC ,LED,IOL= AIsnkSinkcurrentMOD,LED20mARMTOC hargetimerresistor2250k FIMPEDANCEPARAMETERMINTYPMAXUNITRBATB atteryinputimpedance10M RTSTS inputimpedance10M RSNSSNS inputimpedance10M TIMINGTA= TOPR; VCC= 5 V 20%(unlessotherwisenoted)PARAMETERMINTYP MAXUNITdMTOMTO time-basevariation 5%5% 2001 2010,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback5 ProductFolderLink(s).

5 Bq24401 MTOhold-off period =32bq24401 SLUS497A SEPTEMBER2001 chargecyclewhenit detects ApplicationofpowertoVCC Batteryreplacement ExitfromsleepmodeImmediatelyfollowingini tiation,theICentersa thevoltageontheBATpinis lessthantheinternalthreshold,VLBAT, fullydepletedpack,thebq24401enablestheMO Dpintotrickle-chargeata "Top-OffandPulse-TrickleMaintenanceCharg e," thetricklepulse-widthis user-selectableandis ,theLEDpinblinksata 1 Hzrate, (tricklecharge)hasraisedthevoltageontheB ATpinaboveVLBAT, theICentersfastcharge,if aboveVLBAT andthetemperatureis (CurrentRegulation)Followingchargequalif ication(whichincludestricklecharge,if required),thebq24401beginsfastchargefast usinga ,it monitorschargetime,temperature, ,theLEDpinis pulledlow(theLEDis on).

6 Followingfastcharge,thebatteryis toppedoff,if top-offis ,if (constantcurrent)NiCdorNiMHBatteries(VBA T< VMCV always) (rateoftemperaturerise,maximumchargetime = 1 MTO) (optional) ,thebq24401avoidsearlyterminationduetoan initialriseinthebatterytemperaturebydisa blingtherateoftemperaturerise( T/ t) fixedattheprogrammedvalueofthemaximumcha rgetime(MTO)dividedby32.(1)6 SubmitDocumentationFeedbackCopyright 2001 2010,TexasInstrumentsIncorporatedProduct FolderLink(s):bq24401bq244012RC76 VSSVCCCMTORMTOMTOMTOMTO = RC35,988 SEPTEMBER2001 , thetimerexpireswhilestillinfastcharge,th ebq24401proceedstotop-offcharge(iftop-of fis enabled) top-offis enabled, showsa (MTO)forthebq24401:(2)MTOis measuredinminutes,RMTO inohms,andCMTO infarads.

7 ( fordetails.)If,duringfastcharge,VTS> VLTF, thenthetimeris pausedandtheICentersbatteryconditioningc hargeuntilVTS< VLTF. SincetheICis inthebatteryconditioningstate,theLEDflas hesatthe1 <VLTF, fastchargerestartsandthetimerresumesfrom whereit leftoffwithnochangein negative-coefficientthermistor,reference dtoVSSandplacedinthermalcontactwiththeba ttery,maybeusedasa showsa ,thebq24401comparesthebatterytemperature toaninternalhigh-temperaturecutoffthresh old,VTCO, anda low-temperaturethreshold,VLTF. Duringfastchargeonly,theVHTF faultcomparatorisCopyright 2001 2010,TexasInstrumentsIncorporatedSubmitD ocumentationFeedback7 ProductFolderLink(s):bq24401200160180140 12010080604020432124681050100150200250R- kMTOWP ulsewidth - msShows Tolerancebq24401 SLUS497A SEPTEMBER2001 lowerthanVTCO, thebq24401terminatesfastcharge,movestoth echargesuspendedstate, , thebq24401willresumecharginginthetrickle maintenancechargestate,perFigure2.

8 Infastcharge,whenthevoltageontheTSpinis higherthanVLTF, thechargerentersthebatteryconditioningst ate, rateoftemperaturerise( T/ t) ,it samplestheTSpinvoltageevery8 secondsandcomparesit tothevaluemeasured2 thisvoltagedeclinesata rateofVCC/161(V/min).Figure4 showsa ,thebq24401brieflyturnsoffmostcircuits(t heMODandRCpinswillbothgolow)inordertoget thecleanestpossible, continuous, , ,thecapacitancevalueofCMTO connectedbetweentheRCpinandVCC(seeFigure 3) F,andthevalueoftheresistorconnectedtothi spinshouldbelessthan250k . Todisabletop-off, started,thetimeris resetandtop-offproceedsuntilthetimerexpi res,VMCVis reached,orthereisa ,currentis deliveredtothebatteryin , VTS> VLTF, top-offis suspended,thetimerispaused, , VTS< VHTF, allchargingstops, > VHTF, top-offis resumed,if thereis thereis nottimeleft,tricklemaintenancechargeis VTS< VTCO, > ,thebq24401trickle-chargesthebatterybyen ablingtheMODpintochargeata ,connectedbetweentheRCpinandVSS.

9 Figure5 showstherelationshipbetweenthetricklepul se-widthandthevalueofRMTO. Thetypicaltoleranceofthepulsewidthbelow1 50k is 10%. 2001 2010,TexasInstrumentsIncorporatedProduct FolderLink(s) SEPTEMBER2001 REVISEDMARCH2010 NotethatwithanRMTO valuearound150k , thetricklechargepulsewidthis (1/16ofa secondfora 1 Afastchargecurrent).WithRMTO valuesnear150k , it canbedifficulttotellwhichstatetheICis in(top-offortricklecharge).Thebestwaytot ellif thebq24401is ,theRCpiniscountingandhasa sawtoothwaveformonit. Intricklecharge,thereis notimerandtheRCpinis ata determiningwhatstatethebq24401is in,sinceit theRCpinis low(aroundVSSpotential),theICis in sleepmode.

10 (IftheRCpinis lowforbriefinstantsduringfastcharge,theb q24401issamplingtheTSpinfor T/ t).If theRCpinisatsomeDCvalue(usuallyaround1-2 V),thentheIChaspausedthetimerorthetimeri s theRCpinis a sawtoothwaveform(similartoFigure14), thenthetimeris runningandtheRCpinis considered active. Lastly,theRCpincanbeloadedbytoolargeofa trianglewaveformonanoscilloscope(therise timeis lengthened),ortheRCsignalcouldhavetheapp earanceofbeingclipped(flattoporbottom).T hetimeris unreliableundertheseconditionsandthebq24 401shouldnotbeoperatedin (Vss)Chargequalification(includingbatter yconditioning(tricklecharge)andchargeN/A 1-2 VDClevelsuspended)VTS< VLTFA ctiveFastcharge(currentregulation)VTS> VLTF(inbatteryconditioningstate)1-2 VDClevel(timeris pausedandwillresumewhenVTS< VLTF)VTS> VLTF(intricklemaintenancecharge1-2 VDClevel(timeris pausedandwillstate)resumewhenVTS< VLTF)Top-offchargeVLTF> VTS> VHTFA ctiveActive(timeris stillcounting,eventhoughVHTF> VTS> VTCO chargingis suspended)Tricklemaintenancecharge(after fastcharge)