U8655
Maintenance Manual
9 Principles and Failure Analysis
Issue 1.0 (2012-02-23)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
36
The following table describes the signal definitions.
Category
Description
Name in the Circuit
Network
MSM7225A GPIO/PM8029
MPP
Power supply
Digital power supply
input
VREG_S3
VREG_S3 (PM8029)
Analog power input
VREG_L12_2P85
VREG_L12_2P85 (PM8029)
Data
MIPI data
MIPI_DSI_LANE1_P
MIPI_DSI_LANE1_P
MIPI data
MIPI_DSI_LANE1_N
MIPI_DSI_LANE1_N
Synchronization
signal
Frame synchronization
clock
MDP_VSYNC_P
GPIO97
Clock signal
MIPI clock
MIPI_DSI_CLK_P
MIPI_DSI_CLK_P
MIPI clock
MIPI_DSI_CLK_N
MIPI_DSI_CLK_N
Control signal
Reset signal
LCD_RESET_N
GPIO129
Identification
signal
LCD model identification LCD_ID0
GPIO9 (PM8029)
LCD model identification LCD_ID1
GPIO10 (PM8029)
U8666's LCD backlight control:
The U8666 uses a 3.5-inch LCD whose backlight is provided by six LEDs connected in series.
The backlight LEDs are controlled by the backlight driver chip TPS61160A. The ground
resistance of the driver chip pin FB is set to 10 Ω, providing up to 20 mA current to the LEDs
(duty:100%). The backlight brightness (driver output current) is controlled by the PWM
signal.