UM0497
Using the external USB controller
13/21
3
Using the external USB controller
Before using the external USB controller, you must remove all jumpers (JP1, JP3, JP12,
JP13, JP14 and JP15). After that you need to do the connections as mentioned in
. To use the external USB controller in order to control the charging operation,
you must do the following steps:
1.
First disable the SHDN_CHG pin by making it low to switch off the charger.
2.
Do the proper enumeration of the USB cell to increase the current limit up to 500 mA.
3.
During battery charging, as the USB controller is also being powered by a USB, the
power consumption of the system should be kept at less than 150 mA, otherwise we
may not achieve the targeted 250 mA charging current.
4.
After completing steps 1, 2 and 3, enable the SHDN_CHG pin to high to enable
charging operation.
5.
Connect the battery.
6.
Start monitoring the status of the battery charging by monitoring the status pin ST1 and
ST2. Using these status pins, you can control the activity of the external USB controller
to minimize the current consumption while the battery is being charged.
7.
Disable the SHDN_CHG pin again by making it low to reduce any consumption by the
charger.
8.
Follow steps 1 to 7
to charge another battery.
