BQ2084-V140_14 Datasheet, PDF (37/64 Pages) Texas Instruments – SBS v1.1-COMPLIANT GAS GAUGE FOR USE WITH THE bq29312

bq2084-V140
www.ti.com
SLUS664B – JULY 2005 – REVISED AUGUST 2006
Voltage() (0x09)
Description: Returns the cell-pack voltage (mV).
Purpose: The Voltage() function provides power management systems with an accurate battery terminal
voltage. Power management systems can use this voltage, along with battery current information, to
characterize devices they control. This ability helps enable intelligent, adaptive power-management systems.
SMBus protocol: Read word
Output: Unsigned integer—battery terminal voltage in mV.
Units: mV
Range: 0 to 20,000 mV
Granularity: 1 mV
Accuracy: ±0.25% (after calibration)
Current() (0x0a)
Description: Returns the current being supplied (or accepted) by the battery (mA).
Purpose: The Current() function provides a snapshot for the power management system of the current flowing
into or out of the battery. This information is of particular use in power-management systems because they can
characterize individual devices and tune their operation to actual system power behavior.
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
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). AverageCurrent() is implemented as a single pole IIR filter with a
14.5-s time constant.
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 RelativeStateOfCharge() is more likely
between 50% and 60%. The bq2084-V140 sets MaxError() to 100% on a full reset. The bq2084-V140 sets
MaxError() to 2% on completion of a learning cycle, unless the bq2084-V140 limits the learning cycle to the
+512/-256 mAh maximum adjustment values. If the learning cycle is limited, the bq2084-V140 sets MaxError() to
8% unless MaxError() was already below 8%. In this case, MaxError() does not change. The bq2084-V140
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%.
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