BQ2060SS Datasheet, PDF (12/59 Pages) Texas Instruments – SBS V1.1-COMPLIANT GAS GAUGE IC

bq2060
SLUS035E – JANUARY 2000 – REVISED OCTOBER 2005
www.ti.com
The interval at which RM is reduced is given by the following equation, where n is the appropriate factor of 2 n =
¼ , ½ , 1, 2, . . . ):
Self−DischargeUpdateTime +₂₅₆
640
n
13500
(Y% per day)
seconds
(2)
The timer that keeps track of the self-discharge update time is halted whenever charge activity is detected. The
timer is reset to zero if the bq2060 reaches the RemainingCapacity()=FullChargeCapacity() condition while
charging.
Example: If T = 35°C (n = 2) and programmed self-discharge rate Y is 2.5 (2.5% per day at 25°C), the bq2060
reduces RM by RM/256 (0.39%) every
256
640
n
13500
(Y% per
day)
+
6750
seconds
(3)
Figure 7. Self-Discharge at 2.5%/Day @25°C
This means that a 0.39% reduction of RM is made 12.8 times per day to achieve the desired 5% per day
reduction at 35°C.
Figure 7 illustrates how the self-discharge estimate algorithm adjusts RemainingCapacity() versus temperature.
Light Discharge Or Suspend Current Compensation
The bq2060 can be configured in two ways to compensate for small discharge currents that produce a signal
below the digital filter. First, the bq2060 can decrement RM and DCR at a rate determined by the value stored in
Light Discharge Current EE 0x2b when it detects no discharge activity and the SMBC and SMBD lines are high.
Light Discharge Current has a range of 44 µA to 11.2 mA.
Alternatively, the bq2060 can be configured to disable the digital filter for discharge when the SMBC and SMBD
lines are high. In this way, the digital filter does not mask the leakage current signal. The bq2060 is configured in
this mode by setting the NDF bit in Control Mode.
Midrange Capacity Corrections
The bq2060 applies midrange capacity corrections when the VCOR bit is set in Pack Configuration. The bq2060
adjusts RM to the associated percentage at three different voltage levels: VOC25, VOC50, and VOC75. The
VOC values represent the open-circuit battery voltage which RM corresponds to the associated state of charge
for each threshold.
THRESHOLD
VOC25
VOC50
VOC75
ASSOCIATED STATE OF CHARGE
25%
50%
75%
12