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UMTS/HSPA Module Series

UC20 Hardware Design

UC20_Hardware_Design Confidential / Released 43 / 82

3.12. USB Interface

UC20 contains one integrated Universal Serial Bus (USB) transceiver which complies with the USB 2.0

specification and supports high speed (480 Mbps), full speed (12 Mbps) and low speed (1.5 Mbps) mode.

The USB interface is primarily used for AT command, data transmission, GNSS NMEA sentences output,

software debug and firmware upgrade. The following table shows the pin definition of USB interface.

Table 13: USB Pin Description

Pin Name

Pin No.

I/O

Description

Comment

USB_DP

USB differential data bus (positive).

Require differential

impedance of 90Ω.

USB_DM

USB differential data bus (minus).

Require differential

impedance of 90Ω.

USB_VBUS

Used for detecting the USB interface

connected.

3.0~5.25V.

Typical 5.0V.

GND

Ground.

More details about the USB 2.0 specifications, please visit http://www.usb.org/home.

The following figure shows the reference circuit of USB interface.

Module

USB_VBUS

USB_DP

USB_DM

GND

USB connector

Close to USB connector

Differential layout

USB_VBUS

USB_DP

USB_DM

GND

ESD Array

NM_2pF

Figure 24: Reference Circuit of USB Application

In order to ensure the USB interface design corresponding with the USB 2.0 specification, please comply

with the following principles.

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