BQ2085 Datasheet, PDF (29/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2085
SLUS541 – OCTOBER 2002
Units: mA
Range: –32,768 to 32,767 mA
Granularity: 1 mA
Accuracy: 0.25% or 5 mA, whichever is greater
AverageCurrent( ) (0x0b)
Description: Returns a value that approximates a one-minute rolling average of the current being supplied (or
accepted) through the battery terminals (mA). The AverageCurrent( ) function returns values equivalent to
Current( ) during the battery’s first minute of operation.
Purpose: The AverageCurrent( ) function provides the average current flowing into or out of the battery for the
power management system.
SMBus protocol: Read word
Output: Signed integer—charge/discharge rate in mA increments-positive for charge, negative for discharge.
Units: mA
Range: –32,768 to 32,767 mA
Granularity: 1 mA
Accuracy: 0.25% or 5 mA, whichever is greater
MaxError( ) (0x0c)
Description: Returns the expected margin of error (%) in the state of charge calculation. For example, when
MaxError( ) returns 10% and RelativeStateOfCharge( ) returns 50%, the Relative StateOfCharge( ) is more
likely between 50% and 60%. The bq2085 sets MaxError( ) to 100% on a full reset. The bq2085 sets MaxError( )
to 2% on completion of a learning cycle, unless the bq2085 limits the learning cycle to the +512/-256 mAh
maximum adjustment values. If the learning cycle is limited, the bq2085 sets MaxError( ) to 8% unless
MaxError( ) was already below 8%. In this case MaxError( ) does not change. The bq2085 increments
MaxError( ) by 1% after four increments of CycleCount( ) without a learning cycle.
If voltage-based corrections are applied to the coulomb counter, MaxError( ) is set to 25%.
Purpose: The MaxError( ) function has real value in two ways: first, to give the user a confidence level about
the state of charge and second, to give the power management system information about how aggressive it
should be, particularly as the battery nears the end of its life.
SMBus protocol: Read word
Output: Unsigned integer—percent uncertainty for selected information.
Units: %
Range: 2–100%
Granularity: 1%
Accuracy: Not applicable
RelativeStateOfCharge( ) (0x0d)
Description: Returns the predicted remaining battery capacity expressed as a percentage of
FullChargeCapacity( ) (%).
Purpose: The RelativeStateOfCharge( ) function is used to estimate the amount of charge remaining in the
battery relative to the last learned capacity.
SMBus protocol: Read word
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