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3.2.1 Power on and startup
3.2.1 Power on and startup
There are three methods to power-on the handset system (When VBAT >= 3.2V)
Push PWRKEY (Pull the PWRKEY pin to the low level)
Pulling PWRKEY low is the typical way to turn on the handset. The VCORE buck converter will be turned on,
the VIO28/VA LDOs and VUSB LDO, VRF/VTCXO LDOs will be turned on finally. The supplies for the baseband
will be ready, and the system reset will end at the moment when the LDOs is fully turned on to ensure the
correct timing and function. After that, the baseband will send the PWRBB signal back to the PMU for
acknowledgement. To successfully power-on the handset, PWRKEY should be kept low until the PMU receives
the PWRBB from the baseband.
RTC module generates PWRBB to wake up the system.
If the RTC module is scheduled to wake up the handset at some time, the PWRBB signal will directly be sent to
the PMU. In this case, PWRBB will become high at a specific moment and allow PMU to be powered-on just
like the sequence described above. The function is called "RTC alarm"
Valid charger plug-in (CHRIN voltage is within the valid range.)
Plugging in the charger will also turn on the handset if the charger is valid (no OVP taken place). However, if
the battery voltage is too low to power-on the handset (UVLO state), the system will not be turned on by any
powered-on automatically as long as the battery voltage is high enough.
Under-Voltage Lockout(UVLO)
The UVLO state in the PMU prevents start-ups if the initial voltage of the main battery is below the 3.2V
threshold. When the battery voltage is gradually lowering, it will enter the UVLO state, and the PMU will be
turned off by itself, except for VRTC LDO, to prevent further discharging.
LGE Internal Use Only
LGE Internal Use Only
Copyright © 2012 LG Electronics. Inc. All right reserved.
17
O nly for training and service purposes
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Copyright © 01 LG Electronics. Inc. All right reserved.
3. TECHNICAL BRIEF
3. TECHNICAL BRIEF
Only for training and service purposes
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