LTE Module Series
SC20 Charging User Guide
SC20_Charging_User_Guide Confidential / Released 12 / 14
4 Charge
4.1. Charging Process
Charging processes consists of four stages: trickle charging, constant current charging, constant voltage
charging and charging termination.
1. Trickle Charging
When battery voltage is lower than 3.2V, it is called trickle charging stage. This stage can be divided into
two phases: when battery voltage is lower than 2.8V, it is in first phase, and the current is 90mA. When
the voltage is greater than 2.8V and less than 3.2V, it is in the second phase, and the current is 450mA. In
trickle charging , it is the hardware that controls the charging behavior.
2. Constant Current Charging
The software system has been booted up in this stage, and it controls the charging behavior. The USB
charging current is 450mA and AC charging current is 1440mA.
3. Constant Voltage Charging
This stage begins when the battery voltage reaches VDD.
4. Charging Termination
Since pm8909 does not have ADC to detect current, so it is based on the battery capacity to judge the
charging status. When the value is100%, it indicates the charging is ended.
4.2. Set Power-on/off Voltage
Customer can set power-on voltage in boot_images\core\systemdrivers\pmic\config\msm8909\pm8909\
pm_config_target.c.
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