Power Block - LG GT540 Service Manual

3. TECHNICAL BRIEF

3.10 Power Block

3.10.1. General
MSM7227, included RF, is fully covered by PM7540 (Qualcomm PMIC). PM7540 cover the power of MSM7227, MSM
memory, RF block, Bluetooth, USIM and TCXO.
Major power components are :
PM7540 (U403) : Phone main PMIC
RT9393GQW (U601) : LCD BLT Charge Pump
NUS5530 (Q400) : main power path switch( battery charging circuit)
MAX14528 (U402) : OVP(Over voltage protection) IC
3.10.2 PM7540
The PM7540 device (Figure) integrates all wireless handset power management. The power management portion
accepts power from all the most common sources – battery, external charger, adapter, coin cell back-up – and
generates all the regulated voltages needed to power the appropriate handset electronics. It monitors and controls
the power sources, detecting which sources are applied, verifying that they are within acceptable operational limits,
and coordinates battery and coin cell recharging while maintaining the handset electronics supply voltages. Eight
programmable output voltages are generated using low dropout voltage regulators, all derived from a common
trimmed voltage reference. A dedicated controller manages the TCXO warm-up and signal buffering, and key
parameters (under-voltage lockout and crystal oscillator signal presence) are monitored to protect against
detrimental conditions. MSM device controls and statuses the PM7540 IC using Single-wire SBI(SSBI) supplemented
by an Interrupt Manager for time-critical information. Another dedicated IC Interface circuit monitors multiple
trigger events and controls the power-on sequence.
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