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5.3.5BatteryDetectionUsingtheBI/TOUTPin
bq27500
bq27501
System-SideImpedanceTrack™FuelGauge
SLUS785–SEPTEMBER2007
forthefuelgaugetotakeanaccurateOCVreading.Todisablethesefunctions,theBAT_GDpinismerely
sethigh(floatingoutputpulledhigh).OnceanOCVreadinghasbemade,theBAT_GDpinispulledlow,
therebyenablingbatterychargingandregulardischargeofthebattery.TheOperationConfiguration
[BATG_POL]bitcanbeusedtosetthepolarityofthebatterygoodsignal,shouldthedefaultconfiguration
needtobechanged.
TheflowchartofFigure5-1detailshowtheBAT_GDpinfunctionsinthecontextofbatteryinsertionand
removal,aswellasNORMALvsSLEEPmodes.
InPFC1,theBAT_GDpinisalsousedtodisablebatterychargingwhenthebq27500/1readsbattery
temperaturesoutsidetherangedefinedby[ChargeInhibitTempLow,ChargeInhibitTempHigh].The
BAT_GDlineisreturnedtolowoncetemperaturefallswithintherange[ChargeInhibitTempLow+
TempHys,ChargeInhibitTempHigh–TempHys].
Duringpower-uporHIBERNATEactivities,oranyotheractivitywherethebq27500/1needstodetermine
whetherabatteryisconnectedornot,thefuelgaugeappliesatestforbatterypresence.First,the
BI/TOUTpinisputintohigh-Zstatus.Theweak1.8MΩpull-upresistorwillkeepthepinhighwhileno
batteryispresent.Whenabatteryisinserted(orisalreadyinserted)intothesystemdevice,theBI/TOUT
pinwillbepulledlow.Thisstateisdetectedbythefuelgauge,whichpollsthispineverysecondwhenthe
gaugehaspower.Abatterydisconnectedstatusisassumedwhenthebq27500/1readsathermistor
voltagethatisnear2.5V.
FUNCTIONALDESCRIPTION 24SubmitDocumentationFeedback