STW4102_08 Datasheet, PDF (18/34 Pages) STMicroelectronics – Dual USB/wall adapter Li-ion battery charger with gas gauge

Battery charger
STw4102
6.2
Trickle charge
The trickle charge mode is enabled when the battery voltage V_batt is lower than the trickle
voltage threshold V_trickle. An internal current source charges the battery. When V_batt is
above V_trickle, the trickle current generator is off and the battery is charged using the
constant current method.
The trickle voltage threshold and trickle current are defined by OTP configuration bits and
are factory set to 2.9 V and 60 mA by default. Other values are possible, see Section 9:
Factory OTP options on page 24.
6.3
Charging from a wall adapter
The MAIN input is used for charging from a wall adapter or a dedicated USB charger. The
SEL_DC_USB bit (bit 5 of register REG_CHG0) must be set to 0. The fast charge current is
defined by the external resistor R_set connected to the ISET pin, and can be set up to 1 A.
The value of the fast charge current is given by the following formula:
I_charge = 12000 / R_set
In the constant voltage mode, the charger output voltage is regulated with 1% accuracy. The
charger output voltage is programmable using the REG_CHG0 register, bits 3 and 4 (see
Table 11).
Table 11. Charger output voltage
REG_CHG0[4]
REG_CHG0[3]
0
0
0
1
1
0
1
1
V_charge
4.10V +/-1%
4.20V +/-1%
4.30V +/-1%
4.35V +/-1%
Figure 20. Main charge mode
I_batt
Battery Voltage
I_charge
(defined by R_set)
Charge current
V_batt
V_charge
Flag end of
charge (10% I_charge)
V_trickle (2.9v)
I_trickle (60mA)
Trickle
charge
Fast charge
Constant current
Maintenance
charge
Constant voltage
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