BQ2085 Datasheet, PDF (46/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2085
SLUS541 – OCTOBER 2002
Electronics
Load
+
BEL
3
Change Control
Charging Voltage
The 16-bit value, Charging Voltage DF 0x39–0x3a programs the ChargingVoltage( ) value broadcast to a smart
charger. It also sets the base value for determining overvoltage conditions during charging and voltage
compliance during a constant-voltage charging methodology. It is stored in mV.
Over Voltage
The 16-bit value, Over Voltage Margin DF 0x5a–0x5b, sets the limit over ChargingVoltage( ) in mV that is to be
considered as an overvoltage charge-suspension condition.
Charging Current
ChargingCurrent( ) values are either broadcast to a Level 2 smart battery charger or read from the bq2085 by
a Level 3 smart battery charger. The bq2085 sets the value of ChargingCurrent( ), depending on the charge
requirements and charge conditions of the pack.
When fast charge is allowed, the bq2085 sets ChargingCurrent( ) to the rate programmed in Fast-Charging
Current DF 0x3d–0x3e. Fast-Charging Current is stored in mA.
When fast charge terminates, the bq2085 sets ChargingCurrent( ) to zero and then to the Maintenance
Charging Current DF 0x3f, 0x40 when the termination condition ceases. The desired maintenance current is
stored in mA.
When Voltage( ) is less than EDV0, the bq2085 sets ChargingCurrent( ) to Precharge Current DF 0x41, 0x42.
Typically this rate is larger than the maintenance rate to charge a deeply depleted pack up to the point where
it may be fast charged. The desired precharge rate is stored in mA.
If temperature is between 0° and the precharge threshold PC (°C), the bq2085 sets ChargingCurrent( ) to
PreCharge Current. The threshold is programmed in the Precharge Temp DF 0x43.
Precharge
Temp
+
PC (°C)
0.1
(10)
The bq2085 also sets ChargingCurrent( ) to the precharge rate if Voltage( ) is less than the value programmed
in Precharge Voltage DF 0x3b–0x3c. Precharge Voltage is programmed in mV.
Charge Suspension
During charge, the bq2085 compares the current to the ChargingCurrent( ) plus the value in OverCurrent Margin
DF 0x5c–0x5d. If the pack is charged at a current above or equal to the ChargingCurrent( ) plus the programmed
value, the bq2085 sets ChargingCurrent( ) to zero to stop charging.
The desired Overcurrent Margin is programmed in mA.
The desired temperature threshold for charge suspension, MAXTEMP (°C), is programmed in Max
Temperature DF 0x53, 0x54 and is stored as shown:
Max Temperature +
MAXTEMP
0.1
(11)
The bq2085 clears the maximum temperature condition when Temperature( ) drops by the amount
programmed in Temperature Hysteresis DF 0x55 from MAXTEMP or when the temperature is less than or equal
to 43.0°C. Temperature Hysteresis is stored in °C.
The bq2085 suspends fast charge when fast charge continues past full by the amount programmed in Maximum
Overcharge DF 0x4e-0x4f. Maximum Overcharge is programmed in mAh.
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