User's Guide

xE922-3GR Hardware User Guide
1VV0301272 Rev.0.8 2017-01-05
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Reserved. Page 50 of 112
6.1.2. Switching ON due to charging
If an external charger is detected the system startup procedure begins. An external charger can be detected by
LOW level detection on CHG_POK and / or CHG_INT input pins. Both pins have an internal pullup applied
to V_RTC. (See chapter 7.2 for charger IC connections)
6.1.3. Switching on due to RTC alarm
The real time clock can generate a wake-up signal called RTC alarm. Once the PMU detects this level high
the system startup procedure begins.
6.2. Power off
There are two ways to trigger a power off cycle of the system.
6.2.1. Soft power off
Based on application specific implementation and/or user interaction, the SW can trigger a power off cycle.
6.2.2. Emergency power off
In case the PMU detects a HW failure, the PMU will shut down by itself.
The following events will trigger an emergency power off:
· PMU watchdog time-out
· ON_OFF key pressed for more than 10 sec
· ADC_VBATMEAS < threshold ( default 2.3V)
Overtemperature (refer to thermal design guide)
6.3. Reset
For soft reset, the system SW can trigger two types of soft reset.
One type will reset the DBB and go through the PMU power off/on sequence,
The other type will only reset the CPU while keeping voltage regulators enabled.
For hard reset, the system can be reset by pulling LGA pin AU5 “MAIN_RESET_IN” active LOW.