BQ2085 Datasheet, PDF (15/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2085
SLUS541 – OCTOBER 2002
D Overcurrent: An overcurrent condition exists when the bq2085 measures the charge current to be equal
to or greater than Overcurrent Margin plus ChargingCurrent( ). Overcurrent Margin is programmed in DF
0x5c–0x5d. On detecting an overcurrent condition, the bq2085 sets the ChargingCurrent( ) to zero and sets
the TERMINATE_CHARGE_ALARM bit in Battery Status( ). The overcurrent condition and TERMINATE_
CHARGE_ALARM are cleared when the measured current drops below Overcurrent Margin.
D Overvoltage: An overvoltage condition exists when the bq2085 measures the battery voltage to be more
than Over Voltage Margin plus ChargingVoltage( ), or when a cell voltage has exceeded the overvoltage
limit programmed in Cell Over Voltage. Over Voltage Margin is programmed in DF 0x5a–0x5b and Cell Over
Voltage in DF 0x60. On detecting an overvoltage condition, the bq2085 sets the ChargingCurrent( ) to zero
and sets the TERMINATE_CHARGE_ALARM bit in BatteryStatus( ). The bq2085 clears the TERMINATE_
CHARGE_ALARM bit when it detects that the battery is no longer being charged (DISCHARGING bit set
in BatteryStatus( )). The bq2085 continues to broadcast zero charging current until the overvoltage
condition is cleared. The overvoltage condition is cleared when the measured battery voltage drops below
the ChargingVoltage( ) plus the Over Voltage Margin and all cell voltages are less than the Cell Over Voltage
Reset threshold in DF 0xcf, 0xd0.
D Overtemperature: An overtemperature condition exists when Temperature( ) is greater than or equal to the
Max Temperature value programmed in DF 0x53, 0x54. On detecting an overtemperature condition, the
bq2085 sets the ChargingCurrent( ) to zero and sets the OVER_TEMP_ALARM and
TERMINATE_CHARGE_ ALARM bit in BatteryStatus( ) and the CVOV bit in pack status. The
overtemperature condition is cleared when Temperature( ) is equal to or below (Max Temperature –
Temperature Hysteresis DF 0x55, 0x56) or 43°C.
D Overcharge: An overcharge condition exists if the battery is charged more than the Maximum Overcharge
value after RM = FCC. Maximum Overcharge is programmed in DF 0x4e-0x4f. On detecting an overcharge
condition, the bq2085 sets the ChargingCurrent( ) to zero and sets the OVER_CHARGED_ALARM,
TERMINATE_CHARGE_ ALARM, and FULLY_CHARGED bits in BatteryStatus( ). The bq2085 clears the
TERMINATE_CHARGE_ ALARM when it detects that the battery is no longer being charged and clears the
OVER_CHARGED_ALARM when 2mAh of discharge are measured. The FULLY_CHARGED bit remains
set and the bq2085 continues to broadcast zero charging current until RelativeStateOfCharge( ) is less than
Fully Charged Clear% programmed in DF 0x47. The counter used to track overcharge capacity is reset with
2 mAh of discharge.
D Undertemperature: An undertemperature condition exists if Temperature( ) < 0°C. On detecting an under
temperature condition, the bq2085 sets ChargingCurrent( ) to zero. The bq2085 sets ChargingCurrent( )
to the appropriate precharge rate or fast-charge rate when Temperature( ) ≥ 0°C.
Primary Charge Termination
The bq2085 terminates charge if it detects a charge-termination condition based on current taper. A
charge-termination condition includes the following:
For current taper, ChargingVoltage( ) must be set to the pack voltage desired during the constant-voltage
phase of charging. The bq2085 detects a current taper termination when the pack voltage is greater than or
equal to ChargingVoltage( ) minus Current Taper Qual Voltage in DF 0x4a and the charging current is below
a threshold determined by Current Taper Threshold in DF 0x48–0x49 and above 22.5 mA for two
consecutive 40-second intervals.
Once the bq2085 detects a Primary Charge Termination, the bq2085 sets the
TERMINATE_CHARGE_ALARM and FULLY_CHARGED bits in BatteryStatus( ), and sets the
ChargingCurrent( ) to the maintenance charge rate as programmed in Maintenance Charging Current DF
0x3f, 0x40. On termination, the bq2085 also sets RM to a programmed percentage of FCC, provided that
RelativeStateOfCharge( ) is below the desired percentage of FCC and the CSYNC bit in Gauge
Configuration DF 0x29 is set. The programmed percentage of FCC, Fast Charge Termination %, is set in DF
0x46. The bq2085 clears the FULLY_CHARGED bit when RelativeStateOfCharge( ) is less than the
programmed Fully Charged Clear %. The bq2085 broadcasts the fast-charge rate when the
FULLY_CHARGED bit is cleared and voltage and temperature permit. The bq2085 clears the
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