System Power Up - Nokia c2-00 Service Manual

RM-704
System Module
• Drive vibrator.
• Support Bluetooth and FM module through UART and I2S ports.

System power up

The system power up sequence can be seen in the following figure.
The Power-on reset (POR) circuit and the LPBG are directly connected to the battery, If the battery voltage
exceeds the POR threshold (2.5V), the POR is released, the LRTC and LPMU voltage are switched on and the
internal PMU oscillator is started.
The power up sequence can be initiated by any of the following ways if there is a battery of a valid voltage
of above SYSONLEV (3.2V):
• First connect of VBAT with valid voltage has been detected
• Input "On" pin pressed ( goes from low to high)
• Input RTCOUT caused by programmed alarm in RTC block
• A valid charger detected and the battery is charged above the SYSONPRE voltage level
• A USB cable has been connected (external circuit)
The first startup of the PMU is based on local 50 kHz PMU oscillator. This eliminates delays caused by slow
startup time of the 32 kHz RTC oscillator. The SW can later change the input for the PMU clock to the 32 kHz
oscillator and switch off the PMU oscillator to save power. The PMU power up sequence is shown in the figure
below:
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