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bq27501
System-SideImpedanceTrack™FuelGauge
SLUS785–SEPTEMBER2007
4.1.1.7NominalAvailableCapacity():0x0c/0x0d
Thisread-onlycommandpairreturnstheuncompensated(noorlightload)batterycapacityremaining.
UnitsaremAhperbit.
4.1.1.8FullAvailableCapacity():0x0e/0x0f
Thisread-onlycommandpairreturnstheuncompensated(noorlightload)capacityofthebatterywhen
fullycharged.UnitsaremAhperbit.FullAvailableCapacity()isupdatedatregularintervals,asspecified
bytheITalgorithm.
4.1.1.9RemainingCapacity():0x10/0x11
Thisread-onlycommandpairreturnsthecompensatedbatterycapacityremaining.UnitsaremAhperbit.
4.1.1.10FullChargeCapacity():0x12/13
Thisread-onlycommandpairreturnsthecompensatedcapacityofthebatterywhenfullycharged.Units
aremAhperbit.FullChargeCapacity()isupdatedatregularintervals,asspecifiedbytheITalgorithm.
4.1.1.11AverageCurrent():0x14/0x15
Thisread-onlycommandpairreturnsasignedintegervaluethatistheaveragecurrentflowthroughthe
senseresistor.Itisupdatedevery1second.UnitsaremAperbit.
4.1.1.12TimeToEmpty():0x16/0x17
Thisread-onlyfunctionreturnsanunsignedintegervalueofthepredictedremainingbatterylifeatthe
presentrateofdischarge,inminutes.Avalueof65535indicatesbatteryisnotbeingdischarged.
4.1.1.13TimeToFull():0x18/0x19
Thisread-onlyfunctionreturnsanunsignedintegervalueofpredictedremainingtimeuntilthebattery
reachesfullcharge,inminutes,baseduponAverageCurrent().Thecomputationaccountsforthetaper
currenttimeextensionfromthelinearTTFcomputationbasedonafixedAverageCurrent()rateofcharge
accumulation.Avalueof65535indicatesthebatteryisnotbeingcharged.
4.1.1.14StandbyCurrent():0x1a/0x1b
Thisread-onlyfunctionreturnsasignedintegervalueofthemeasuredstandbycurrentthroughthesense
resistor.TheStandbyCurrent()isanadaptivemeasurement.Initiallyitreportsthestandbycurrent
programmedinInitialStandby,andafterspendingsometimeinstandby,reportsthemeasuredstandby
current.
Theregistervalueisupdatedevery1secondwhenthemeasuredcurrentisabovetheDeadband(3mA
default)andislessthanorequalto2xInitialStandby.Thefirstandlastvaluesthatmeetthiscriteriaare
notaveragedin,sincetheymaynotbestablevalues.Toapproximatea1minutetimeconstant,eachnew
StandbyCurrent()valueiscomputedasfollows:
StandbyCurrent()
NEW
=(239/256)×StandbyCurrent()
OLD
+(17/256)×AverageCurrent().
4.1.1.15StandbyTimeToEmpty():0x1c/0x1d
Thisread-onlyfunctionreturnsanunsignedintegervalueofthepredictedremainingbatterylifeatthe
standbyrateofdischarge,inminutes.ThecomputationusesNominalAvailableCapacity(NAC),the
uncompensatedremainingcapacity,forthiscomputation.Avalueof65535indicatesbatteryisnotbeing
discharged.
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