Blu LIFE 8, Service Manual, Page: 27 / 29

4.9 Charge function:
PMU managed charge function and PMU integrated in CPU IC of LIFE 8 project. AC or
USB charger plugged in from micro USB connector, VCHG signal into CPU so the CPU
detect the charger plugged in, CPU output control signal to enable PMOS (U301), the
charging current will go through PMOS (U301) and via a restense(R309) to battery. PinB4
(ISENSE) to detect charging current and pinA4 (BATSENSE) detect the battery voltage in
charging process.
If no charging function, please check if any message displayed in screen or battery bar
twinkle in top right corner of screen. If any hint in screen that means detected charger fail,
check the charger is a good part or measure charger’s output, then check the connection
between phone and charger. Exclude external problem, you need to check mainboard issue
step by step. First, check the PMOS’ soldering , then check PMOS’ control signal, high
level is disable and low level is enable, difference voltage level from low to high level,
difference voltage level to control the difference charging current, low voltage level is right
in charging process. If PMOS and it’s control signal are OK, check the connection between
battery and battery connector, check the battery itself at last. Notice, if the battery voltage
less than 3.3V, the charging current is less than 100mA for long time( less than one
hour)and the phone couldn’t power on, so was no hint any.
To Battery
connector
Charge PMOS FET
Charging current
and voltage detect Battery
voltage detect