Power Key And System Power-Up - Nokia 301 Service Manual

RM-839; RM-840; RM-841
System Module

Power key and system power-up

Figure 41 Power on key
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 with a valid voltage above SYSONLEV (3.2V):
• First connect of VBAT with valid voltage has been detected
• RTC alarm by baseband (rtcout_i)
• Power-on key (ON_OFF1): by Short ON_OFF1 with VRTC. Note that this signal can only be used for issuing a
power-on event, not a power-off event.
• Charger detection by companion IC (PWR_ON_CMP)
System start-up sequence
• Analog start up circuit
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