STw4102 STMicroelectronics, STw4102 Datasheet - Page 17

• Manufacturer Part Number: STw4102
• Description: Dual source USB Li-ion charger with gas gauge
• Manufacturer: STMicroelectronics

STw4102
6
6.1
Figure 19. Charge flow (simplified)
Power detected (PWRDETECTN LOW)
Battery charger
Charge cycle
The charge cycle is initiated when the presence of a power source on either the MAIN or
USBPWR inputs is detected (the PWRDETECTN pin goes low), while the charger is
enabled by the CHG_ENA bit of the REG_CHG1 control register. If both supplies are
connected, the MAIN input path is selected.
The EOCHG output pin is driven low as the charge begins. If the battery voltage is lower
than the trickle threshold, the charge cycle begins in trickle mode with a low current (default
value: 60 mA) until the battery voltage reaches the trickle voltage threshold (default value:
2.9 V). Once the battery voltage rises above this threshold, the charger enters into fast
charge mode where the programmed charge current I
battery.
When the battery voltage approaches the programmable charge voltage (4.10V, 4.20V,
4.30V or 4.35V), the charger enters into a constant voltage charging mode and the charging
current decreases. When the current level reaches the end-of charge level (10% of I
the EOCHG status pin is switched off (open) to indicate that the battery is almost fully
charged, and the charger enters maintenance mode.
In maintenance mode, the charger continues to monitor the battery voltage to maintain the
battery voltage level. The maintenance mode lasts until the charge is stopped by clearing
the CHG_ENA bit in the REG_CHG1 control register, or by removing the power source
(PWRDETECTN is opened).
I
charge
V
batt
EOCH OPEN (LED OFF)
< 2.8v
EOCH LOW (LED ON)
EOCH LOW (LED ON)
> 15%
EOCH OPEN (LED OFF)
Maintenance charge
CCCV is still ON
Trickle charge
CCCV charge
Charge Off
60mA
V
I
charge
batt
> 2.9v
< 10%
Power removed (PWRDETECTN OPEN)
Battery overvoltage
or Watchdog event
charge
EOCH OPEN (LED OFF)
Battery overvoltage
or Watchdog event
Charge Stopped
or I
USB
is supplied to the
Battery charger
charge
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),