User's Manual

UMTS/HSPA Module Series
UG96 Hardware Design
UG96_Hardware_Design Confidential / Released 43 / 75
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
9
IO
USB differential data bus (positive).
Require differential
impedance of 90Ω.
USB_DM
10
IO
USB differential data bus (minus).
Require differential
impedance of 90Ω.
USB_VBUS
8
PI
Used for detecting the USB interface
connected.
2.5~5.25V.
Typical 5.0V.
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
NM_2pF
ESD
NM
NM
Rs
Rs
Figure 25: 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:
 It is important to route the USB signal traces as differential pairs with total grounding. The impedance
of USB differential trace is 90ohm.
 Pay attention to the influence of junction capacitance of ESD component on USB data lines. Typically,
the capacitance value should be less than 2pF.
 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 not only upper and
lower layer but also right and left side.