BQ2084-V140_14 Datasheet, PDF (11/64 Pages) Texas Instruments – SBS v1.1-COMPLIANT GAS GAUGE FOR USE WITH THE bq29312

bq2084-V140
www.ti.com
SLUS664B – JULY 2005 – REVISED AUGUST 2006
• Current remains ≤ 3C/32 when EDV2 or Battery Low % level is reached.
• No overload condition exists when EDV2 threshold is reached, or if RM() has dropped to Battery Low% x
FCC,
• No valid charge activity occurs during the discharge period. A valid charge is defined as an uninterrupted
charge of 10 mAh into the battery.
The bq2084-V140 sets VDQ = 1 in PackStatus() when qualified discharge begins. The bq2084-V140 sets VDQ
= 0 if any disqualifying condition occurs. FCC cannot be reduced by more than 256 mAh or increased by more
than 512 mAh during any single update cycle. The bq2084-V140 saves the new FCC value to the data flash
within 4 seconds of being updated.
End-of-Discharge Thresholds and Capacity Correction
The bq2084-V140 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 bq2084-V140 for overall voltage or single-cell EDV
thresholds. If programmed for single-cell EDV determination, the bq2084-V140 determines EDV on the basis of
the lowest single-cell voltage. Fixed EDV thresholds must be programmed in EMF/EDV0 DF 0x95-0x96, EDV C0
Factor/EDV1 DF 0x97-0x98, and EDV R Factor/EDV2 DF 0x99-0x9a.
If the CEDV bit in Gauge Configuration DF 0x29 is set, automatic compensated EDVs are enabled and the
bq2084-V140 computes the EDV0, EDV1, and EDV2 voltage thresholds based on the values in DF 0x95-0xa0
and the battery's current discharge rate and temperature. If FEDV0 in Gauge Configuration is also set then
EDV0 is not compensated. The bq2084-V140 disables EDV detection if Current( ) exceeds the Overload Current
threshold programmed in DF 0x5b-DF 0x5c. The bq2084-V140 resumes EDV threshold detection after Current( )
drops below the Overload Current threshold. Any EDV threshold detected is reset after charge is detected and
VDQ is cleared after 10 mAh of charge.
The bq2084-V140 uses the EDV thresholds to apply voltage-based corrections to the RM register according to
Table 2.
Table 2. State-of-Charge Based on Low Battery Voltage
THRESHOLD
EDV0
EDV1
EDV2
RELATIVE STATE OF CHARGE
0%
3%
Battery Low %
The bq2084-V140 performs EDV-based RM adjustments with Current()≤ C/32. No EDV flags are set if current <
C/32.
The bq2084-V140 adjusts RM as it detects each threshold. If the voltage threshold is reached before the
corresponding capacity on discharge, the bq2084-V140 reduces RM to the appropriate amount as shown in
Table 2.
If an RM % level is reached on discharge before the voltage reaches the corresponding threshold, then RM is
held at that % level until the threshold is reached. RM is only held if VDQ = 1, indicating a valid learning cycle is
in progress. If Battery Low % is set to zero, EDV1 and EDV0 corrections are disabled.
EDV Thresholds and Near-Full Programming
The bq2084-V140 uses the values stored in data flash for the EDV0, EDV1, and EDV2 values or calculates the
three thresholds from a base value and the temperature, capacity, and rate adjustment factors stored in data
flash. If EDV compensation is disabled, then EDV0, EDV1, and EDV2 are stored directly in mV in DF 0x95-0x96,
DF 0x97-0x98, and DF 0x99-0x9a, respectively.
For capacity correction at EDV2, Battery Low % DF 0x2f can be set at a desired state-of-charge,
STATEOFCHARGE%, in the range of 3-19%. Typical values for STATEOFCHARGE% are 5-7%, representing
5-7% capacity.
Battery Low % = (STATEOFCHARGE% x 2.56)
Submit Documentation Feedback
11