Table of Contents
Advertisement
G700-U10 Smartphone
Maintenance Manual
Figure 10-3 Power-on and power-off sequences
Circuit Analysis
When a battery is inserted into the phone, PWRKEY is at high level. When you press the
power key, PWRBT is connected to GND, PWRKEY is pulled down, and an interrupt occurs.
The power supplies start to work in sequence, and the system is powered on.
In detail, the buck power supply for VCORE and VPROC starts at the very beginning, and
then the VIO18 and VIO28 power supplies start in sequence. After all the power supplies that
should be started by default are on and the power-on sequence and power supply requirements
are met, the system is powered on and reset.
After the power-on process is completely carried out, the baseband chip sends the PWRBB
signal to the PM IC to confirm the startup of the system.
To ensure that the phone is properly powered on, the PWRKEY signal should be kept low
until the PM IC receives the PWRBB signal.
The RTC module outputs the PWRBB signal to wake up the system: If the RTC is set to wake
up the system at a predefined time, the PWRBB signal will be directly sent to the PM IC. In
this case, when the set time arrives, the PWRBB signal will be pulled up to start the power-on
sequence of the PM IC. This is the RTC waking-up action.
When an effective charger is connected to the phone, if the charger is detected by the system,
the system will also start in case that the input voltage is within a range where an OVP event
does not occur. However, if the voltage is lower than the UVLO voltage or the battery is not
Issue 1.0 (2013-07-22)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
10 Circuit and Failure Analysis
31
Advertisement
Table of Contents
