BQ2085 Datasheet, PDF (14/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

bq2085
SLUS541 – OCTOBER 2002
For the midrange corrections to occur, the temperature must be in the range of 19°C to 31°C inclusive and the
Current( ) and AverageCurrent( ) must both be between –64 mA and 0. The bq2085 makes midrange
corrections as shown in Table 5. For a correction to occur, the bq2085 must detect the need for correction twice
during subsequent 20-s intervals. With the VCOR bit set, the bq2085 makes midrange corrections whenever
conditions permit. If the OTVC bit in Gauge Configuration DF 0x29 is set and VCOR = 0, the bq2085 makes
a single attempt of mid-range correction immediately after device reset and does not require a second
validation.
Table 5. Midrange Corrections
Voltage( )
CONDITION
≥ VOC75 and RelativeStateOfCharge( ) ≤ 63%
< VOC75 and RelativeStateOfCharge( ) ≥ 87%
≥VOC50 and RelativeStateOfCharge( ) ≤ 38%
<VOC50 and RelativeStateOfCharge( ) ≥ 62%
≥ VOC25 and RelativeStateOfCharge( ) ≤ 13%
< VOC25 and RelativeStateOfCharge( ) ≥ 37%
RESULT
RelativeStateOfCharge( )→75%
RelativeStateOfCharge( )→75%
RelativeStateOfCharge( )→50%
RelativeStateOfCharge( )→50%
RelativeStateOfCharge( )→25%
RelativeStateOfCharge( )→25%
Charge Control
Charging Voltage and Current Broadcasts
The bq2085 supports SBS charge control by broadcasting the ChargingCurrent( ) and ChargingVoltage( ) to
the Smart Charger address. The bq2085 broadcasts the requests every 10 seconds. The bq2085 updates the
values used in the charging current and voltage broadcasts based on the battery’s state of charge, voltage, and
temperature. The charge voltage is programmed in Charging Voltage DF 0x039-0x3a. The charge current may
take any of four different values: Fast Charging Current DF (0x3d–0x3c), Maintenance Charging Current (DF
0x3f), Precharge Current (0x41), or 0. The charge current depends on charge state and operating conditions.
The bq2085 internal charge control is compatible with the constant current/constant voltage profile for Li-Ion.
The bq2085 detects primary charge termination on the basis of the tapering charge current during the
constant-voltage phase.
Alarm Broadcasts to Smart Charger and Host
If any of the bits 8–15 in BatteryStatus( ) are set, the bq2085 broadcasts an AlarmWarning( ) message to the
Host address. If any of the bits 12–15 in BatteryStatus( ) are set, the bq2085 also sends an AlarmWarning( )
message to the Smart Charger address. The bq2085 repeats the AlarmWarning( ) messages every 10 seconds
until the alarm bits are cleared.
Precharge Qualification
The bq2085 sets ChargingCurrent( ) to the precharge rate as programmed in Precharge Current DF 0x41 under
the following conditions:
D Voltage: The bq2085 requests the precharge charge rate when Voltage( ) drops below the precharge
threshold or when the EDV0 threshold is detected. Once requested, a precharge rate remains until
Voltage( ) increases above the precharge threshold and the EDV0 condition does not exist. The precharge
threshold is programmed in Precharge Voltage DF 0x3b–0x3c.
D Temperature: The bq2085 requests the precharge rate when Temperature( ) is between 0°C and the
precharge threshold programmed in Precharge Temp 0x43. Temperature( ) must be equal to or greater than
the precharge threshold to allow the fast-charge rate.
Charge Suspension
The bq2085 may temporarily suspend charge if it detects a charging fault. A charging fault includes the following
conditions.
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