BQ25895_16 Datasheet, PDF (22/67 Pages) Texas Instruments – Adjustable Voltage 3.1-A Boost Operation

bq25895
SLUSC88A – MARCH 2015 – REVISED MAY 2016
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8.2.7 Battery Charging Management
The device charges 1-cell Li-Ion battery with up to 5-A charge current for high capacity battery. The 11-mΩ
BATFET improves charging efficiency and minimize the voltage drop during discharging.
8.2.7.1 Autonomous Charging Cycle
With battery charging is enabled (CHG_CONFIG bit = 1 and CE pin is low), the device autonomously completes
a charging cycle without host involvement. The device default charging parameters are listed in Table 4. The
host can always control the charging operations and optimize the charging parameters by writing to the
corresponding registers through I²C.
Table 4. Charging Parameter Default Setting
DEFAULT MODE
Charging Voltage
Charging Current
Pre-charge Current
Termination Current
Temperature Profile
Safety Timer
bq25895
4.208 V
2.048 A
128 mA
256 mA
Cold/Hot
12 hour
A new charge cycle starts when the following conditions are valid:
• Converter starts
• Battery charging is enabled by setting CHG_CONFIG bit, /CE pin is low and ICHG register is not 0 mA
• No thermistor fault on TS pin
• No safety timer fault
• BATFET is not forced to turn off (BATFET_DIS bit = 0)
The charger device automatically terminates the charging cycle when the charging current is below termination
threshold, charge voltage is above recharge threshold, and device not in DPM mode or thermal regulation. When
a full battery voltage is discharged below recharge threshold (threshold selectable via VRECHG bit), the device
automatically starts a new charging cycle. After the charge is done, either toggle CE pin or CHG_CONFIG bit
can initiate a new charging cycle.
The STAT output indicates the charging status of charging (LOW), charging complete or charge disable (HIGH)
or charging fault (Blinking). The STAT output can be disabled by setting STAT_DIS bit. In addition, the status
register (CHRG_STAT) indicates the different charging phases: 00-charging disable, 01-precharge, 10-fast
charge (constant current) and constant voltage mode, 11-charging done. Once a charging cycle is completed, an
INT is asserted to notify the host.
8.2.7.2 Battery Charging Profile
The device charges the battery in three phases: preconditioning, constant current and constant voltage. At the
beginning of a charging cycle, the device checks the battery voltage and regulates current / voltage.
VBAT
<2V
2V–3V
>3V
Table 5. Charging Current Setting
CHARGING CURRENT
I_BATSHORT
I_PRECHG
I_CHG
REG DEFAULT SETTING
–
128 mA
2048 mA
CHRG_STAT
01
01
10
22
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