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HUAWEI EM820W HSPA+ PC Embedded Module
Hardware Guide
Description of the Application Interfaces
Issue 01 (2010-12-09)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
9
Figure 3-1
HUAWEI EM820W power supply time sequence.
Parameter Remarks
Time(Nominal value)
Unit
Tpd
Power Valid to USB D+ high
3.45
sec
3.5 USB Signals
The EM820W is compliant with USB 2.0 specification. It supports full-speed (12
Mbit/s) and high-speed (480 Mbit/s) modes when acting as a peripheral and supports
low-speed, full-speed, and high-speed modes when acting as a host. The USB 2.0
specifications allow peripherals to support any one or more of these speeds. To
ensure best performance, the PC USB host controller should support high-speed
mode when using the EM820W USB high-speed mode.
Table 3-3
USB pins
Name
Pin
Description
Direction to Module
USB D-
36
USB data signal D-
Input/output
USB D+
38
USB data signal D+
Input/output
To minimize the RF radiation through the PCI-E interface, you can add a 33 pF ceramic
capacitor in the ground on every pin of the PCI-E on the host side except USB D+/D-.
The USB interface is powered directly from the 3.3 V supply. The USB input/output
lines are compatible with the USB2.0 3.3 V signal specifications.
Table 3-4
USB signal DC characteristics
VOHmin VOLmax
VIHmin
VILmax
2.8 V
0.3 V
2 V
0.8 V