U8185
Maintenance Manual
9 Principles and Failure Analysis
Issue 1.0 (2012-03-23)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
19
The MSM7X2XA (the U8185 uses the MSM7225A) is the baseband signal processing chip,
mainly responsible for processing the input and output of IMAGE, VIDEO, AUDIO, RF
INTERFACES, and CONECTIVIT Y signals. The baseband chip provides keypad, LCD,
microSD card, Wi-Fi, camera, and microphone interfaces.
The PM8029 provides analog multi-channel switch, real-time clock circuit, TCXO clock
circuit, motor driver circuit, and programmable current source.
The RTR6285A is the RF signal processing chip, responsible for converting uplink/downlink
RF signals.
The PCBA can be divided into four sub-systems: baseband, RF, power supply, and user
interfaces.
9.2 Baseband Unit
9.2.1 Power-on Management Circuits
Figure 9-2
Circuit schematic diagram