BQ2060A_15 Datasheet, PDF (12/61 Pages) Texas Instruments – SBS v1.1-Compliant Gas Gauge IC

bq2060A
SLUS500D – OCTOBER 2001 – REVISED OCTOBER 2011
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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 bq2060A initializes DCR to FCC –
RM when FCC-RM is less than 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 bq2060A 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 + (FCCxBatteryLow%)
(1)
Where:
BatteryLow% = (value stored in EE 0x54) + 2.56
A qualified discharge occurs if the battery discharges from RM ≥ FCC - Near Full × 2 to the EDV2 voltage
threshold with the following conditions:
• No valid charge activity occurs during the discharge period. A valid charge is defined as an input of 10 mAh
into the battery.
• No more than 256 mAh of self-discharge and/or light discharge estimation occurs during the discharge period.
• The temperature does not drop below 5°C during the discharge period.
• The battery voltage reaches the EDV2 threshold during the discharge period and the voltage was between
the EDV2 threshold and [EDV2 threshold – 256 mV] when the bq2060A detected EDV2.
• No midrange voltage correction occurs during the discharge period.
• No overload condition occurs when voltage ≤ EDV2 threshold
FCC cannot be reduced by more than 256 mAh or increased by more than 512 mAh during any single update
cycle. FCC becomes invalid if it is initialized or updated to a value less then 256 mAH. FCC becomes invalid if it
is initialized or updated to a value less than 256 mAH. The bq2060A saves the new FCC value to the EEPROM
within 4 s of being updated.
End-of-Discharge Thresholds and Capacity Correction
The bq2060A monitors the battery for three low-voltage thresholds, EDV0, EDV1, and EDV2. The EDV
thresholds are programmed in EDVF/EDV0 EE 0x72–0x73, EMF/EDV1EE 0x74–0x75, and EDV C1/C0 Factor
/EDV2 EE 0x78–0x79. If the CEDV bit in Pack Configuration is set, automatic EDV compensation is enabled, and
the bq2060A computes the EDV0, EDV1, and EDV2 thresholds based on the values in EE 0x72–0x7d, 0x06,
and the battery load current, temperature, capacity, and cycle count. The bq2060A disables EDV detection if
Current() exceeds the Overload Current threshold programmed in EE 0x46–EE 0x47. The bq2060A resumes
EDV threshold detection after the Current() drops below the overload current threshold. Any EDV threshold
detected is reset after 10 mAh of charge is applied.
The bq2060A uses the thresholds to apply voltage-based corrections to the RM register according to Table 4.
Table 4. State of Charge Based on Low Battery
Voltage
THRESHOLD
EDV0
EDV1
EDV2
STATE OF CHARGE IN RM
0%
3%
Battery Low %
The bq2060A adjusts RM as it detects each threshold. If the voltage threshold is reached before the
corresponding capacity on discharge, the bq2060A reduces RM to the appropriate amount as shown in Table 4.
If RM reaches the capacity level before the voltage threshold is reached on discharge, the bq2060A prevents RM
from decreasing until the battery voltage reaches the corresponding threshold, but only on a full learning-cycle
discharge (VDQ = 1). The EDV1 threshold is ignored if Miscellaneous Options bit 7 = 1.
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