BQ2084DBTR-V150 Datasheet, PDF (12/69 Pages) Texas Instruments – SBS v1.1-COMPLIANT GAS GAUGE WITH LED DELAY

bq2084-V150
SLUS758 – JUNE 2007
www.ti.com
bq2084-V150 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-V150 disables EDV detection if Current( ) exceeds the Overload Current
threshold programmed in DF 0x5b-DF 0x5c. The bq2084-V150 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-V150 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-V150 performs EDV-based RM adjustments with Current() ≤ C/32. No EDV flags are set if current <
C/32.
The bq2084-V150 adjusts RM as it detects each threshold. If the voltage threshold is reached before the
corresponding capacity on discharge, the bq2084-V150 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-V150 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)
The bq2084-V150 updates FCC if a qualified discharge occurs from a near-full threshold of FCC - Near Full,
until EDV2 condition is reached. The desired near-full threshold window is programmed in Near Full in DF 0x30,
0x31 in mAh.
EDV Discharge Rate and Temperature Compensation Programming
If EDV compensation is enabled, the bq2084-V150 calculates battery voltage to determine EDV0, EDV1, and
EDV2 thresholds as a function of battery capacity, temperature, and discharge load. The general equation for
EDV0, EDV1, and EDV2 calculation is
EDV0,1,2 = n (EMF × FBL – | ILOAD | × R0 × FTZ)
EMF is a no-load cell voltage higher than the highest cell EDV threshold computed. EMF is programmed
in mV in EMF/EDV1 DF 0x95-0x96.
ILOAD is the current discharge load magnitude.
n = the number of series cells
FBL is the factor that adjusts the EDV voltage for battery capacity and temperature to match the no-load
characteristics of the battery.
FBL = f ( C0, C + C1, T )
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