BQ2084-V140_14 Datasheet, PDF (12/64 Pages) Texas Instruments – SBS v1.1-COMPLIANT GAS GAUGE FOR USE WITH THE bq29312

bq2084-V140
SLUS664B – JULY 2005 – REVISED AUGUST 2006
www.ti.com
The bq2084-V140 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-V140 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 )
C (either 0%, 3%, or Battery Low % for EDV0, EDV1, and EDV2, respectively) and C0 are the
capacity-related EDV adjustment factors. C0 is programmed in EDV C0 Factor/EDV1 DF 0x97-98. C1 is
the desired residual battery capacity remaining at EDV0 (RM = 0). The C1 factor is stored in EDV C1
Factor DF 0xa0.
T is the current temperature in °K.
R0 × FTZ represents the resistance of a cell as a function of temperature and capacity.
FTZ = f ( R1, T0, T, C + C1, TC)
R0 is the first order rate dependency factor stored in EDV R0 Factor/EDV2 DF 0x99-0x9a.
T is the current temperature; C is the battery capacity relating to EDV0, EDV1, and EDV2.
R1 adjusts the variation of impedance with battery capacity. R1 is programmed in EDV R1 Rate Factor
DF 0x9d-0x9e.
T0 adjusts the variation of impedance with battery temperature. T0 is programmed in EDV T0 Rate
Factor DF 0x9b-0x9c.
TC adjusts the variation of impedance for cold temperatures (T < 23°C). TC is programmed in EDV TC
DF 0x9f.
Typical values for the EDV compensation factors, based on overall pack voltages for a Li-ion 3s2p 18650 pack,
are:
EMF = 11550/3
T0 = 4475
C0 = 235
C1 = 0
R0 = 5350/3
R1 = 250
TC = 3
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