BQ25895_16 Datasheet, PDF (23/67 Pages) Texas Instruments – Adjustable Voltage 3.1-A Boost Operation

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bq25895
SLUSC88A – MARCH 2015 – REVISED MAY 2016
If the charger device is in DPM regulation or thermal regulation during charging, the charging current can be less
than the programmed value. In this case, termination is temporarily disabled and the charging safety timer is
counted at half the clock rate.
Regulation Voltage
(3.84V t 4.608V)
Fast Charge Current
(128mA-5056mA)
VBAT_LOWV (2.8V/3V)
Battery Voltage
Charge Current
VBAT_SHORT (2V)
IPRECHARGE (64mA-1024mA)
ITERMINATION (64mA-1024mA)
IBATSHORT (100mA)
Trickle Charge Pre-charge
Fast Charge and Voltage Regulation
Figure 13. Battery Charging Profile
Safety Timer
Expiration
8.2.7.3 Charging Termination
The device terminates a charge cycle when the battery voltage is above recharge threshold, and the current is
below termination current. After the charging cycle is completed, the BATFET turns off. The converter keeps
running to power the system, and BATFET can turn on again to engage Supplement Mode.
When termination occurs, the status register CHRG_STAT is set to 11, and an INT pulse is asserted to the host.
Termination is temporarily disabled when the charger device is in input current, voltage or thermal regulation.
Termination can be disabled by writing 0 to EN_TERM bit prior to charge termination.
8.2.7.4 Resistance Compensation (IRCOMP)
For high current charging system, resistance between charger output and battery cell terminal such as board
routing, connector, MOSFETs and sense resistor can force the charging process to move from constant current
to constant voltage too early and increase charge time. To speed up the charging cycle, the device provides
resistance compensation (IRCOMP) feature which can extend the constant current charge time to delivery
maximum power to battery.
The device allows the host to compensate for the resistance by increasing the voltage regulation set point based
on actual charge current and the resistance as shown below. For safe operation, the host should set the
maximum allowed regulation voltage register (V_CLAMP) and the minimum resistance compensation (BATCOMP).
V_{REG_ACTUAL} = VREG + min(I_{CHRG_ACTUAL} x BATCOMP, V_CLAMP)
(1)
8.2.7.5 Thermistor Qualification
8.2.7.5.1 Cold/Hot Temperature Window in Charge Mode
The device continuously monitors battery temperature by measuring the voltage between the TS pins and
ground, typically determined by a negative temperature coefficient thermistor (NTC) and an external voltage
divider. The device compares this voltage against its internal thresholds to determine if charging is allowed. To
initiate a charge cycle, the battery temperature must be within the V_LTF to V_HTF thresholds. During the charge
cycle the battery temperature must be within the V_LTF to V_TCO thresholds, else the device suspends charging and
waits until the battery temperature is within the V_LTF to V_HTF range.
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