BQ2083-V1P3 Datasheet, PDF (10/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2083-V1P3
SLVS508 − OCTOBER 2003
www.ti.com
The main charge counter RemainingCapacity( ) (RM) represents the available capacity or energy in the battery at
any given time. The bq2083−V1P3 adjusts RM for charge, self-discharge, and other compensation factors. The
information in the RM register is accessible through the SMBus interface and is also represented through the LED
display.
The FullChargeCapacity( ) (FCC) register represents the last measured full discharge of the battery. It is used as
the battery full-charge reference for relative capacity indication. The bq2083−V1P3 updates FCC after the battery
undergoes a qualified discharge from nearly full to a low battery level. FCC is accessible through the SMBus interface.
The Discharge Count Register (DCR) is a non-accessible register that tracks discharge of the battery. The
bq2083−V1P3 uses the DCR register to update the FCC register if the battery undergoes a qualified discharge from
nearly full to a low battery level. In this way, the bq2083−V1P3 learns the true discharge capacity of the battery under
system use conditions.
Main Gas-Gauge Registers
The gas-gauge register functions are described in Table 3.
RemainingCapacity( ) (RM)
RM represents the remaining capacity in the battery. The bq2083−V1P3 computes RM in units of either mAh or
10 mWh depending on the selected mode. See Battery Mode( ) (0x03) for units configuration.
RM counts up during charge to a maximum value of FCC and down during discharge and self-discharge to a minimum
of 0. In addition to charge and self-discharge compensation, the bq2083−V1P3 calibrates RM at three
low-battery-voltage thresholds, EDV2, EDV1, and EDV0 and three programmable midrange thresholds VOC25,
VOC50, and VOC75. This provides a voltage-based calibration to the RM counter.
DesignCapacity( ) (DC)
The DC is the user-specified battery full capacity. It is calculated from Pack Capacity DF 0x31-0x32 and is
represented in units of mAh or 10 mWh. It also represents the full-battery reference for the absolute display mode.
FullChargeCapacity( ) (FCC)
FCC is the last measured discharge capacity of the battery. It is represented in units of either mAh or 10 mWh,
depending on the selected mode. On initialization, the bq2083−V1P3 sets FCC to the value stored in Last Measured
Discharge DF 0x35-0x36. During subsequent discharges, the bq2083−V1P3 updates FCC with the last measured
discharge capacity of the battery. The last measured discharge of the battery is based on the value in the DCR register
after a qualified discharge occurs. Once updated, the bq2083−V1P3 writes the new FCC value to data flash in mAh
to Last Measured Discharge. FCC represents the full battery reference for the relative display mode and relative state
of charge calculations.
Discharge Count Register (DCR)
The DCR register counts up during discharge, independent of RM. DCR counts discharge activity, battery load
estimation, and self-discharge increment. The bq2083−V1P3 initializes DCR, at the beginning of a discharge, to FCC
− RM when RM is within the programmed value in Near Full DF 0x2f. The DCR initial value of FCC − RM is reduced
by FCC/128 if SC = 1 (bit 5 in Gauge Configuration) and is not reduced if SC = 0. DCR stops counting when the battery
voltage reaches the EDV2 threshold on discharge.
Capacity learning (FCC Update) and Qualified Discharge
The bq2083−V1P3 updates FCC with an amount based on the value in DCR if a qualified discharge occurs. The new
value for FCC equals the DCR value plus the programmable nearly full and low battery levels, according to the
following equation:
FCC (new) + DCR (final) + DCR (initial) ) Measured Discharge to EDV2 ) (FCC Battery Low%)
(1)
Battery Low % = (value stored in DF 0x2e) ÷ 2.56
A qualified discharge occurs if the battery discharges from RM ≥ FCC − Near Full to the EDV2 voltage threshold with
the following conditions:
D No valid charge activity occurs during the discharge period. A valid charge is defined as a charge of 10 mAh into
the battery.
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