BQ2013H Datasheet, PDF (4/24 Pages) Texas Instruments – Gas Gauge IC for Power- Assist Applications

bq2013H
Register Backup
The bq2013H RBI input pin is intended to be used with
a storage capacitor to provide backup potential to the in-
ternal bq2013H registers when V_CC momentarily drops be-
low 3.0V. V_CC is output on RBI when V_CC is above 3.0V.
After V_CC rises above 3.0V, the bq2013H checks the internal
registers for data loss or corruption. If data has changed,
then the NAC register is cleared, and the LMD register is
loaded with the initial PFC.
Voltage Thresholds
In conjunction with monitoring V_SR for charge/discharge
currents, the bq2013H monitors the battery potential
through the SB pin for the end-of-discharge voltage (EDV)
thresholds.
The EDV threshold levels are used to determine when
the battery has reached an “empty” state.
The EDV thresholds for the bq2013H are set as follows:
EDV1 (first) = 1.00V
EDVF (final) = EDV1 - 100mV
The battery voltage divider (RB1 and RB2 in Figure 1) is
used to scale these values to the desired threshold.
If VSB is below either of the two EDV thresholds for the
specified delay times in Table 1, the associated flag is
latched and remains latched, independent of VSB, until
the next valid charge. EDV monitoring is disabled if the
OVLD bit in FLGS2 is set.
Table 1. Delay Time in Seconds
Capacity
> 40%
20% to 40%
< 20%
< 10°C
7
4
2
Temperature
10°C to 30°C
6
3
2
> 30°C
5
2
2
Reset
The bq2013H can be reset by removing V_CC and ground-
ing the RBI pin for 15 seconds or with a command over
the serial port. The serial port reset command sequence
requires writing 00h to register PPFC (address = leh)
and the writing 00h to register LMD (address = 05h.)
Temperature
The bq2013H internally determines the temperature in
10°C steps centered from -35°C to +85°C. The tempera-
ture steps are used to adapt charge rate compensations
and self-discharge counting. The temperature range is
available over the serial port in 10°C increments as
shown in the following table:
TMPGG (hex)
0x
1x
2x
3x
4x
5x
6x
7x
8x
9x
Ax
Bx
Cx
Temperature Range
< -30°C
-30°C to -20°C
-20°C to -10°C
-10°C to 0°C
0°C to 10°C
10°C to 20°C
20°C to 30°C
30°C to 40°C
40°C to 50°C
50°C to 60°C
60°C to 70°C
70°C to 80°C
> 80°C
Layout Considerations
The bq2013H measures the voltage differential between
the SR and V_SS pins. V_OS (the offset voltage at the SR
pin) is greatly affected by PC board layout. For optimal
results, the PC board layout should follow the strict rule of
a single-point ground return. Sharing high-current
ground with small signal ground causes undesirable noise
on the small signal nodes. Additionally:
I The capacitors should be placed as close as possible
to the SB and V_CC pins and their paths to V_SS should
be as short as possible. A high-quality ceramic
capacitor of 0.1µf is recommended for V_CC.
I The sense resistor (R_S) should be as close as possible
to the bq2013H.
I The R-C on the SR pin should be located as close as
possible to the SR pin. The maximum R should not
exceed 100K.
Gas Gauge Operation
The operational overview diagram in Figure 2 illus-
trates the operation of the bq2013H. The bq2013H ac-
cumulates a measure of charge and discharge currents,
as well as an estimation of self-discharge. The bq2013H
compensates charge current for charge rate and tem-
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