BQ27742-G1 Datasheet, PDF (30/46 Pages) Texas Instruments – Single-Cell Li-Ion Battery Fuel Gauge with Programmable Hardware Protection

bq27742-G1
SLUSBV9C – MARCH 2014 – REVISED FEBRUARY 2016
Typical Applications (continued)
0.1 µF 0.1 µF
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10 Ω
10 Ω
1 µF
0.1 µF
0.1 µF
10 kΩ
(25°C )
0.47 µF
VPWR
BAT
REG25
TS
NC
RC2
VSS
4.7 kΩ
SRN
SRP
PACKP
CHG
DSG
SDA
SCL
HDQ
5 mΩ
200 Ω
200 Ω
0.1 µF 0.1 µF
0.1 µF
1 kΩ
100 Ω
100 Ω
PACK+
1 kΩ
2 kΩ
0.1 µF
0.1 µF
0.1 µF
HDQ
PACK–
Figure 20. HDQ Mode Schematic
8.2.2 Design Requirements
Several key parameters must be updated to align with a given application's battery characteristics. For highest
accuracy gauging, it is important to follow-up this initial configuration with a learning cycle to optimize resistance
and maximum chemical capacity (Qmax) values prior to sealing and shipping packs to the field. Successful and
accurate configuration of the fuel gauge for a target application can be used as the basis for creating a "golden"
gas gauge (.GG) file that can be written to all production packs, assuming identical pack design and Li-Ion cell
origin (chemistry, lot, etc.). Calibration data can be included as part of this golden GG file to cut down on battery
pack production time. If going this route, it is recommended to average the calibration data from a large sample
size and use these in the golden file. Ideally, it is recommended to calibrate all packs individually as this will lead
to the highest performance and lowest measurement error in the end application on a per-pack basis. In addition,
the integrated protection functionality should be correctly configured to ensure activation based on the fault
protection needs of the target pack design, or else accidental trip could be possible if using defaults. Table 11,
Key Data Flash Parameters for Configuration, shows the items that should be configured to achieve reliable
protection and accurate gauging with minimal initial configuration.
NAME
Design Capacity
Design Energy
Table 11. Key Data Flash Parameters for Configuration
DEFAULT
1000
3800
UNIT
mAh
mWh
RECOMMENDED SETTING
Set based on the nominal pack capacity as interpreted from cell manufacturer's
datasheet. If multiple parallel cells are used, should be set to N * Cell Capacity.
Set based on the nominal pack energy (nominal cell voltage * nominal cell
capacity) as interpreted from the cell manufacturer's datasheet. If multiple parallel
cells are used, should be set to N * Cell Energy.
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