U8185
Maintenance Manual
9 Principles and Failure Analysis
Issue 1.0 (2012-03-23)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
30
Table 9-1
Circuit diagram signal summary
Signal
Description
Reference Measurement
or Wave Form
VCHG
Charging current input from a charger
Used for detecting the connection of a charger
Detection range: 0–18 V
VPH_PWR
Main power supply, supplying power to the main chip's
power unit
Voltage range: 0–4.2 V
BAT_FET_N
Control signal of the MOS (Q201)
VBAT
Input end for battery voltage detection and output end
for trickle charging.
Battery voltage, range: 0–4.2
V
VCOIN
Backup power supply, NC
When sudden loss of power occurs, the backup
power supply (if any) will supply power to the
phone until the main battery power recovers, so that
the phone will not shut down.
None.
BATT_THERM
Battery temperature detection.
Detects the voltage of the thermistor inside the
battery to determine the battery's temperature.
Cd
VREG_S1
Supplies power to the processor core.
1.1 V
VREG_S2
Supplies power to the MSM application processor.
1.1 V
VREG_S3
Supplies power to the memory and digital I/O.
1.8 V
VREG_S4
Supplies power to the RF and analog section.
2.35 V
VREG_L1
NC
VREG_L2
Supplies power to the RF's front end.
VREG_L3
Supplies power to the MIPI DSI circuit.
VREG_L4
Supplies power to the digital PLL.
VREG_L5
VREG_L6
NC
VREG_L7
Supplies power to the MSM's analog section.
VREG_L8
TCXO power supply; controlled by internal TCXO.
2.85 V
VREG_L9
Supplies power to the MIPI CSI circuit.
VREG_L10
VREG_L11
Supplies power to the eMMC module on the MSM.
VREG_L12
Supplies power to the TCXO_OUT_D1 buffer, AMUX,
and XO ADC circuits.
VREG_L13
Supplies power to the SD circuit.