BQ2060SS Datasheet, PDF (9/59 Pages) Texas Instruments – SBS V1.1-COMPLIANT GAS GAUGE IC

bq2060
www.ti.com
SLUS035E – JANUARY 2000 – REVISED OCTOBER 2005
The main counter RemainingCapacity() (RM) represents the available capacity or energy in the battery at any
given time. The bq2060 adjusts RM for charge, self-discharge, and leakage compensation factors. The
information in the RM register is accessible through the communications ports and is also represented through
the LED display.
The FullChargeCapacity() (FCC) register represents the last measured full discharge of the battery. It is used for
the battery’s full-charge reference for relative capacity indication. The bq2060 updates FCC when the battery
undergoes a qualified discharge from nearly full to a low battery level. FCC is accessible through the serial
communications ports.
The Discharge Count Register (DCR) is a non-accessible register that only tracks discharge of the battery. The
bq2060 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 bq2060 learns the true discharge capacity of the battery under
system-use conditions.
Main Gas Gauge Registers
RemainingCapacity() (RM)
RM represents the remaining capacity in the battery. The bq2060 computes RM in either mAh or 10 mWh
depending on the selected mode.
On initialization, the bq2060 sets RM to 0. RM counts up during charge to a maximum value of FCC and down
during discharge and self-discharge to 0. In addition to charge and self-discharge compensation, the bq2060
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 EE 0x3a–0x3b and is
represented in 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 either mAh or 10 mWh depending
on the selected mode. On initialization, the bq2060 sets FCC to the value stored in Last Measured Discharge EE
0x38–0x39. During subsequent discharges, the bq2060 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 bq2060 writes the new FCC value to EEPROM 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 can continue to count even after RM
has counted down to 0. Prior to RM = 0, discharge activity, light discharge estimation and self-discharge
increment DCR. After RM = 0, only discharge activity increments DCR. The bq2060 initializes DCR to FCC – RM
when RM is within twice the programmed value in Near Full EE 0x55. The DCR initial value of FCC – RM is
reduced by FCC/128 if SC = 0 (bit 2 in Control Mode) and is not reduced if SC = 1. DCR stops counting when
the battery voltage reaches the EDV2 threshold on discharge.
Capacity Learning (FCC Update) And Qualified Discharge
The bq2060 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) ) measureddischarge to EDV2
) (FCCxBatteryLow%)
(1)
where:
BatteryLow% = (value stored in EE 0x54) ÷ 2.56
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