Quectel Wireless Solutions Company Limited 201404UC15M User Manual

UMTS/HSDPA Module Series

UC15 Mini PCIe Hardware Design

UC15_Mini_PCIe_Hardware_Design Confidential / Released 23 / 40

3.6. USB Interface

The following table shows the pin definition of USB interface.

Table 9: USB Pin Description

UC15 Mini PCIe is compliant with USB 2.0 specification. It can only be used as a slave device. Meanwhile,

it supports high speed (480 Mbps), full speed (12 Mbps) and low speed (1.5 Mbps) mode. The USB

interface can be used for AT command, data transmission, software debug and firmware upgrade. The

following figure shows the reference circuit of USB interface.

Module

USB_ DP

USB_DM

GND

MCU

Differential layout

USB_DP

USB_DM

GND

NM_2pF

VCC_MCU

VCC

Figure 8: Reference Circuit of USB Interface

To ensure the USB interface design corresponds with the USB 2.0 specification, please comply with the

following principles.

 It is important to route the USB signal traces as differential pairs with total grounding. The impedance

of USB differential trace is 90ohm.

 Do not route signal traces under crystals, oscillators, magnetic devices and RF signal traces. It is

important to route the USB differential traces in inner-layer with ground shielding, and not only upper

and lower layer but also right and left side should be shielded.

 If you use the USB connector, you should install the ESD components as close to the USB connector

as possible. Pay attention to the influence of junction capacitance of ESD component on USB data

lines. Typically, the capacitance value should be less than 2pF (e.g.ESD9L5.0ST5G).

Pin No.

Pin Name

I/O

Description

Comment

USB_DM

USB differential data (-).

Require differential impedance of 90Ω.

USB_DP

USB differential data (+).

Require differential impedance of 90Ω.