BQ2060SS Datasheet, PDF (11/59 Pages) Texas Instruments – SBS V1.1-COMPLIANT GAS GAUGE IC

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FUNCTION
Pack Status
Pack Configuration
VCELL4
VCELL3
VCELL2
VCELL1
bq2060
SLUS035E – JANUARY 2000 – REVISED OCTOBER 2005
Table 3. bq2060 Register Functions (continued)
COMMAND CODE
SMBus
HDQ16
0x2f (LSB)
0x2f (LSB)
0x2f (MSB)
0x2f (MSB)
0x3c
0x3c
0x3d
0x3d
0x3e
0x3e
0x3f
0x3f
SMBus ACCESS
read/write
read/write
read/write
read/write
read/write
read/write
UNITS
n/a
n/a
mV
mV
mV
mV
Table 4. State of Charge Based on Low Battery Voltage
THRESHOLD
EDV0
EDV1
EDV2
STATE OF CHARGE IN RM
0%
3%
Battery Low %
End-of-Discharge Thresholds And Capacity Correction
The bq2060 monitors the battery for three low-voltage thresholds, EDV0, EDV1, and EDV2. The EDV thresholds
are programmed in EDVF/EDV0 EE 0x72–0x73, EMF/EDV1 EE 0x74–0x75, and EDV C1/C0 Factor/ EDV2 EE
0x78–0x79. If the CEDV bit in Pack Configuration is set, automatic EDV compensation is enabled and the
bq2060 computes the EDV0, EDV1, and EDV2 thresholds based on the values in EE 0x72–0x7d, 0x06, and the
battery’s current discharge rate, temperature, capacity, and cycle count. The bq2060 disables EDV detection if
Current() exceeds the Overload Current threshold programmed in EE 0x46 - EE 0x47. The bq2060 resumes
EDV threshold detection after Current() drops below the overload current threshold. Any EDV threshold detected
is reset after a 10-mAh charge is applied.
The bq2060 uses the thresholds to apply voltage-based corrections to the RM register according to Table 4.
The bq2060 adjusts RM as it detects each threshold. If the voltage threshold is reached before the corresponding
capacity on discharge, the bq2060 reduces RM to the appropriate amount as shown in Table 4. If RM reaches
the capacity level before the voltage threshold is reached on discharge, the bq2060 prevents RM from
decreasing until the battery voltage reaches the corresponding threshold.
Self-Discharge
The bq2060 estimates the self-discharge of the battery to maintain an accurate measure of the battery capacity
during periods of inactivity. The algorithm for self-discharge estimation takes a programmed estimate for the
expected self-discharge rate at 25°C stored in EEPROM and makes a fixed reduction to RM of an amount equal
to RemainingCapacity()/256. The bq2060 makes the fixed reduction at a varying time interval that is adjusted to
achieve the desired self-discharge rate. This method maintains a constant granularity of 0.39% for each
self-discharge adjustment, which may be performed multiple times per day, instead of once per day with a
potentially large reduction.
The self-discharge estimation rate for 25°C is doubled for each 10 degrees above 25°C or halved for each 10
degrees below 25°C. The following table shows the relation of the self-discharge estimation at a given
temperature to the rate programmed for 25°C (Y% per day):
TEMPERATURE (C)
Temp < 10
10 ≤ Temp <20
20 ≤ Temp <30
30 ≤ Temp <40
40 ≤ Temp <50
50 ≤ Temp <60
60 ≤ Temp <70
70 ≤ Temp
SELF-DISCHARGE RATE
¼Y% per day
½Y% per day
Y% per day
2Y% per day
4Y% per day
8Y% per day
16Y% per day
32Y% per day
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