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5.4TEMPERATUREMEASUREMENT
5.5OVERTEMPERATUREINDICATION
5.5.1Overtemperature:Charge
5.5.2Overtemperature:Discharge
5.6CHARGINGANDCHARGE-TERMINATIONINDICATION
5.6.1DetectingChargeTermination
5.6.2ChargeInhibit
bq27500
bq27501
System-SideImpedanceTrack™FuelGauge
SLUS785–SEPTEMBER2007
Thebq27500/1measuresbatterytemperatureviaitsTSinput,inordertosupplybatterytemperature
statusinformationtoImpedanceTrack™andchargercontrolsectionsofthegauge.Alternatively,itcan
alsomeasureinternaltemperatureviaitson-chiptemperaturesensor,butonlyifthe[TEMPS]bitof
OperationConfigurationregisteriscleared.
Regardlessofwhichsensorisusedformeasurement,asystemprocessorcanrequestthecurrentbattery
temperaturebycallingtheTemperature()function(seeSection4.1.1StandardDataCommandsfor
specificinformation).
Therecommendedthermistorcircuitusesanexternal103AT-typethermistor.Additionalcircuitinformation
forconnectingthisthermistortothebq27500/1isshownintheSection8ReferenceSchematic.
Ifduringcharging,Temperature()reachesthethresholdofOTChgforaperiodofOTChgTimeand
AverageCurrent()>ChgCurrentThreshold,thenthe[OTC]bitofFlags()isset.Note:ifOTChgTime=
0thenfeatureiscompletelydisabled.
WhenTemperature()fallstoOTChgRecovery,the[OTC]ofFlags()isreset.
Ifduringdischarging,Temperature()reachesthethresholdofOTDsgforaperiodofOTDsgTime,and
AverageCurrent()≤-DsgCurrentThreshold,thenthe[OTD]bitofFlags()isset.Note:ifOTDsgTime
=0,thenfeatureiscompletelydisabled.
WhenTemperature()fallstoOTDsgRecovery,the[OTD]bitofFlags()isreset.
Forproperbq27500/1operation,thecellchargingvoltagemustbespecifiedbytheuser.Thedefaultvalue
forthisvariableisChargingVoltage=4200mV.
Thebq27500/1detectschargeterminationwhen(1)during2consecutiveperiodsofCurrentTaper
Window,theAverageCurrent()is<TaperCurrentand(2)duringthesameperiods,theaccumulated
changeincapacity>0.25mAh/CurrentTaperWindowand(3)Voltage()>ChargingVoltage–Taper
Voltage.Whenthisoccurs,the[CHG]bitofFlags()iscleared.Also,ifthe[RMFCC]bitofOperation
Configurationisset,andRemainingCapacity()issetequaltoFullChargeCapacity().
WhenPFC=1,thebq27500/1canindicatewhenbatterytemperaturehasfallenbeloworrisenabove
predefinedthresholds(ChargeInhibitTempLowandChargeInhibitTempHigh,respectively).Inthis
mode,theBAT_GDlineismadehightoindicatethiscondition,andisreturnedtoitslowstate,once
batterytemperaturereturnstotherange[ChargeInhibitTempLow+TempHys,ChargeInhibitTemp
High–TempHys].
WhenPFC=0or2,thebq27500/1mustbequeriedbythesysteminordertodeterminethebattery
temperature.Atthattime,thebq27500/1willsamplethetemperature.Thissavesbatteryenergywhen
operatingfrombattery,asperiodictemperatureupdatesareavoidedduringchargingmode.
FUNCTIONALDESCRIPTION 26SubmitDocumentationFeedback