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5.3DETAILEDDESCRIPTIONOFDEDICATEDPINS
5.3.1TheOperationConfigurationRegister
5.3.2PinFunctionCodeDescriptions
5.3.3BAT_LOWPin
5.3.4PowerPathControlwiththeBAT_GDPin
bq27500
bq27501
System-SideImpedanceTrack™FuelGauge
SLUS785–SEPTEMBER2007
Somebq27500/1pinsareconfiguredviatheOperationConfigurationdataflashregister,asindicatedin
Table5-3.Thisregisterisprogrammed/readviathemethodsdesribedinSection4.2.1AccessingtheData
Flash.Theregisterislocatedatsubclass=64,offset=0.
Table5-3.OperationConfigurationBitDefinition
Operationbit7bit6bit5bit4bit3bit2bit1bit0
Cfg
HighByteRESCAP––PFC_CFG1PFC_CFG0IWAKERSNS1RSNS0
LowByte–IDSELENSLEEPRMFCCBATL_POLBATG_POL–TEMPS
RESCAP=No-loadrateofcompensationisappliedtothereservecapacitycalculation.Truewhenset.Defaultis0.
PFC_CFG1/PFC_CFG0=PinFunctionCode(PFC)modeselection:PFC0,1,or2selectedby0/0,0/1,or1/0,respectively.DefaultisPFC
1(0/1).
IWAKE/RSNS1/RSNS0=Thesebitsconfigurethecurrentwakefunction(ref.Table5-3).Defaultis0/0/1.
IDSELEN=Enablescellprofileselectionfeature.Truewhenset.Defaultis1.
SLEEP=Thefuelgaugecanentersleep,ifoperatingconditionsallow.Truewhenset.Defaultis1.
RMFCC=RMisupdatedwiththevaluefromFCC,onvalidchargetermination.Truewhenset.Defaultis1.
BATL_POL=BAT_LOWpinisactive-high.Truewhenset.Defaultis1.
BATG_POL=BAT_GDpinisactive-low.Truewhencleared.Defaultis0.
TEMPS=SelectsexternalthermistorforTemperature()measurements.Truewhenset.Defaultis1.
Thebq27500/1hasthreepossiblepin-functionvariationsthatcanbeselectedinaccordancewiththe
circuitarchitectureoftheendapplication.EachvariationhasbeenassignedaPinFunctionCode,orPFC.
WhenthePFCissetto0,onlythebq27500/1measuresbatterytemperatureunderdischargeand
relaxationconditions.Thechargerdoesnotreceiveanyinformationfromthebq27500/1aboutthe
temperaturereadings,andthereforeoperatesopen-loopwithrespecttobatterytemperature.
APFCof1islikeaPFCof0,excepttemperatureisalsomonitoredduringbatterycharging.Ifcharging
temperaturefallsoutsideofthepresetrangedefinedindataflash,achargercanbedisabledviathe
BAT_GDpin,untilcelltemperaturerecovers.SeeSection5.6.2ChargeInhibitforadditionaldetails.
FinallywhenthePFCissetto2,thebatterythermistorcanbesharedbetweenthefuelgaugeandthe
charger.Thechargerhasfullusageofthethermistorduringbatterycharging,whilethefuelgaugeuses
thethermistorexclusivelyduringdischargeandbatteryrelaxation.
ThePFCisspecifiedinOperationConfiguration[PFC_CFG1,PFC_CFG0].ThedefaultisPFC=1.
TheBAT_LOWpinprovidesasystemprocessorwithanelectricalindicatorofbatterystatus.Thesignaling
ontheBAT_LOWpinfollowsthestatusofthe[SOC1]bitintheFlags()register.Notethatthepolarityof
theBAT_LOWpincanbeinvertedviathe[BATL_POL]bitofOperationConfiguration.
Thebq27500/1mustoperateinconjunctionwithotherelectronicsinasystemappliance,suchaschargers
andotherIC’sandsubcircuitsthatdrawappreciablepower.Afterabatteryisinsertedintothesystem,this
electronicsmustbedisabled,sothatanaccurateOCVcanberead.TheOCVisusedforhelping
determinewhichbatteryprofiletouse,asitconstitutespartofthebatteryimpedancemeasurement.
Whenabatteryisinsertedintoasystem,theImpedanceTrack™algorithmrequiresthatnochargingof
thebatterytakesplaceandthatanydischargeislimitedtolessthanC/20—theseconditionsaresufficient
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