STw4102

Battery charger

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6

Battery charger

6.1

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

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

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).

Figure 19.

Charge flow (simplified)

Trickle charge

60mA

CCCV charge

Maintenance charge

EOCH OPEN (LED OFF)

CCCV is still ON

EOCH LOW (LED ON)

EOCH LOW (LED ON)

Charge Off

EOCH OPEN (LED OFF)

Power detected (PWRDETECTN LOW)

Charge Stopped

EOCH OPEN (LED OFF)

Power removed (PWRDETECTN OPEN)

Battery overvoltage

or Watchdog event

Battery overvoltage

or Watchdog event