U8655
Maintenance Manual
9 Principles and Failure Analysis
Issue 1.0 (2012-02-23)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
54
Touchscreen Panel
Interface
Pin
Description
VDD_2V8_TP
VREG_L12_2P85 (PM8029)
Touchscreen panel analog power supply,
2.85 V
VREG_S3
VREG_S3 (PM8029)
Touchscreen panel digital power supply and
I/O connector power supply, 1.8 V
TOUCH_INT
GPIO_82 (MSM7225A)
Touchscreen panel interrupt signal
I2C1_SCL
GPIO_131 (MSM7225A)
Touchscreen panel's I2C clock
I2C1_SDA
GPIO_132 (MSM7225A)
Touchscreen panel's I2C data
TOUCH_RST_N
GPIO_96 (MSM7225A)
Touchscreen panel reset signal
9.4.15 SIM Card
The MSM7225A is not compatible with the SIM card interface. The PM8029's MPP pins are
used to convert voltage levels of the signals for communication between the MSM7225A and
the SIM card.
The voltage of VREG_L16_UIM1 can be set to 1.5–3.05 V. The USIM interface's operating
voltage is usually 1.8 V or 3.0 V. The following table describes the voltage level conversion
interface of the PM8029.
Signal for Interfacing
with the MSM
Voltage Level
Signal for Interfacing
with the USIM Card
Voltage Level
VREG_S3
UIM1_RESET
VREG_L16_UIM1
(configured by the
phone's firmware)
UIM1_MSM_CLK
UIM1_CLK
UIM1_MSM_DATA
UIM1_DATA
NOTE
Considering that SIM card operations are frequent, transient-voltage-suppression (TVS) diodes are
added to the circuit to provide ESD and surge protection.
USIM card circuit