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HUAWEI EM820W HSPA+ PC Embedded Module
Hardware Guide Description of the Application Interfaces
Issue 01 (2010-12-31)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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Figure 3-1 HUAWEI EM820W power supply time sequence.
Parameter Remarks Time(Nominal value) Unit
Tpd Power Valid to USB D+ high 3.24 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