Only For Training And Service Purposes - LG GB220 Service Manual

3. TECHNICAL BRIEF
3.2.1 Power on and startup
▪ Analog startup Circuit
Because the POR circuit and the LPBG are directly connected to the battery, it is not possible to switch
them off. If the battery voltage exceed the power on reset threshold (2.5V), the power on reset is released,
the LPMU regulator and the LRTC voltage regulator are switched on. The LPMU regulator starts in its ultra-
low power mode
The LPMU regulator generates a control signal (lpmu_OK) that enables the 50KHZ PMU oscillator. The
output clock of the oscillator is checked with a fully coded counter. A counter overflow releases the reset
(vpmu_rst_n) signal for the small PMU state-machine.
▪ Small first digital State-Machine
The small PMU state-machine is always connected to VPMU After starting from reset the small startup state
machine enters the SYSTEM OFF state and only continuous the startup procedure if a switch on event like
first connect, on-key, wake up or charge detect occurs.
▪ PMU-main State-Machine
The main PMU state-machine is always connected to VPMU also. The power up sequence driven by the
PMU state-machine can be seen in Figure18. After enabling the reference (HPGB) and waiting for the
settling time, the battery voltage is measured and compared with the power on threshold. If the battery
voltage is high enough, the SD1 DC/DC converter and the LCORE LDO are started. A timer ensures that the
supply voltage will be stable before the DCXO is enabled. The DCXO settling time is ensured using a fixed
timer. After an overflow of this timer, the reset is released for the rest of the system. The PMU state
machine remains in this System-ON state until the system is switched into the OFF state. For example the
system sleep mode is completely configured by software( for example switching off the LDO's, switching
of the DCXO etc.) and controlled by the VCXO_enable signal. The reason for the startup is stored in the
ResetSourceRead register.
▪ Battery Measurement
LGE Internal Use Only
LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
- 24 - Copyright © 2009 LG Electronics. Inc. All right reserved.

Only for training and service purposes

Only for training and service purposes