BQ2085-V1P2 Datasheet, PDF (11/56 Pages) Texas Instruments – SBS-COMPLIANT GAS GAUGE IC FOR USE WITH THE bq29311

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bq2085−V1P2
SLUS590 − DECEMBER 2003
End-of-Discharge Thresholds and Capacity Correction
The bq2085−V1P2 monitors the battery for three low-voltage thresholds, EDV0, EDV1, and EDV2. The EDV
thresholds can be programmed for determination based on the overall pack voltage or an individual cell level.
The EDVV bit in Pack Configuration DF 0x28 configures the bq2085−V1P2 for overall voltage or single-cell EDV
thresholds. If programmed for single cell EDV determination, the bq2085−V1P2 determines EDV on the basis
of the lowest single-cell voltage. Fixed EDV thresholds can be programmed in EMF/EDV0 DF 0x84-0x85, EDV
C0 Factor/EDV1 DF 0x86-0x87, and EDV R Factor/EDV2 DF 0x88-0x89. If the CEDV bit in Gauge
Configuration DF 0x29 is set, automatic EDV compensation is enabled and the bq2085−V1P2 computes the
EDV0, EDV1, and EDV2 thresholds based on the values in DF 0x84-0x8d and the battery’s current discharge
rate and temperature. The bq2085−V1P2 disables EDV detection if Current( ) exceeds the Overload Current
threshold programmed in DF 0x58 − DF 0x59. The bq2085−V1P2 resumes EDV threshold detection after
Current( ) drops below the Overload Current threshold. Any EDV threshold detected is reset after charge is
applied and VDQ is cleared after 10mAh of charge.
Table 2. State of Charge Based on Low Battery Voltage
THRESHOLD
EDV0
EDV1
EDV2
RELATIVE STATE OF CHARGE
0%
3%
Battery Low %
The bq2085−V1P2 uses the EDV thresholds to apply voltage-based corrections to the RM register according
to Table 1. The bq2085−V1P2 performs EDV-based RM adjustments with Current( ) ≥ C/32. No EDVs are set
if current < C/32. The bq2085−V1P2 adjusts RM as it detects each threshold. If the voltage threshold is reached
before the corresponding capacity on discharge, the bq2085−V1P2 reduces RM to the appropriate amount as
shown in Table 2. This reduction occurs only if current ≥ C/32 when the EDV threshold is detected. If RM
reaches the capacity level before the voltage threshold is reached on discharge, the bq2085−V1P2 prevents
RM from decreasing further until the battery voltage reaches the corresponding threshold only on a full learning
cycle discharge. RM is not held at the associated EDV percentage on a nonlearning discharge cycle (VDQ=0)
or if current < C/32.
If Battery Low % is set to zero, EDV1 and EDV0 corrections are disabled.
Table 3. bq2085−V1P2 Register Functions
FUNCTION
ManufacturerAccess
RemainingCapacityAlarm
RemainingTimeAlarm
BatteryMode
AtRate
AtRateTimeToFull
AtRateTimeToEmpty
AtRateOK
Temperature
Voltage
Current
AverageCurrent
MaxError
RelativeStateOfCharge
AbsoluteStateOfCharge
RemainingCapacity
COMMAND CODE
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0a
0x0b
0x0c
0x0d
0x0e
0x0f
ACCESS
read/write
read/write
read/write
read/write
read/write
read
read
read
read
read
read
read
read
read
read
read
UNITS
NA
mAh, 10 mWh
minutes
NA
mA, 10mW
minutes
minutes
Boolean
0.1°K
mV
mA
mA
percent
percent
percent
mAh, 10 mWh
11