BQ2060A_15 Datasheet, PDF (43/61 Pages) Texas Instruments – SBS v1.1-Compliant Gas Gauge IC

bq2060A
www.ti.com
SLUS500D – OCTOBER 2001 – REVISED OCTOBER 2011
EDV Discharge Rate and Temperature Compensation
If EDV compensation is enabled, the bq2060A calculates battery voltage to determine EDV0, EDV1, and EDV2
thresholds as a function of battery capacity, temperature, and discharge load. (See Figure 11 and Figure 12.)
Battery Low % = 7%, Load = 500 mA
Battery Low % = 7%, Temperature = 35^oC
11500
11500
11000
EDV2
10500
EDV1
10000
9500
9000
8500
45C/500 mA
20C/500 mA
8000
7500
10 9 8 7 6 5 4 3 2 1 0
% Capacity
Figure 11. EDV Calculations vs
Capacity for Various Temperatures
11000
EDV2
10500
EDV1
10000
9500
9000
8500
8000
7500
35C/500mA
35C/1A
35C/2A
EDV0
7000
10 9 8 7 6 5 4 3 2 1 0
% Capacity
Figure 12. EDV Calculations vs
Capacity for Various Loads
The general equation for EDV0, EDV1, and EDV2 calculation is
EDV0,1,2 + EMF F_BL * ^Ť I_LOAD ^Ť R0 F_TZ F_CY
where
• EMF is a no-load battery voltage that is higher than the highest EDV threshold that is computed. EMF is
programmed in mV in EMF/EDV1 EE 0x74–0x75.
• I_LOAD is the current discharge load.
(9)
F_BL is the factor that adjusts the EDV voltage for battery capacity and temperature to match the no-load
characteristics of the battery.
F_BL + f (C0, C ) C1, T)
(10)
where C (0%, 3%, or Battery Low % for EDV0, EDV1, and EDV2, respectively) and C0 are the capacity-related
EDV adjustment factors. C0 is programmed in the lower 11 bits of EDV C1/C0 Factor/EDV2 EE 0x78–79.
The Residual Capacity Factor is stored in the upper 5 bits of EE 0x78–0x79.
Residual Capacity Factor C1 = RESIDUAL% * 2.56.
RESIDUAL% is the desired battery capacity remaining at EDV0 (RM = 0).
• T is the current temperature in K
R0*F_TZ represents the resistance of the battery as a function of temperature and capacity.
F_TZ + f (R1, T0, T, C ) C1, TC)
(11)
• R0 is the first-order rate dependency factor stored in EDV R0 Factor EE 0x7a–0x7b.
• T is the current temperature; C is the battery capacity relating to EDV0, EDV1, and EDV2; and C1 is the
desired residual battery capacity remaining at EDV0 (RM = 0).
• R1 adjusts the variation of impedance with battery capacity. R1 is programmed in EDV R1 Factor EE
0x7c–0x7d.
• T0 adjusts the variation of impedance with battery temperature. T0 is programmed in EDV T0 Factor EE
0x76–0x77.
• TC adjusts the variation of impedance for cold temperature (T < 23°C). TC is programmed in EDV TC EE
0x07.
F_CY is the factor that adjusts for changing cell impedance as the battery pack is cycled:
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