UMTS/HSPA Module Series
UG95 Hardware Design
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3.12. USB Interface
UG95 contains one integrated Universal Serial Bus (USB) transceiver which complies with the USB
1.1/2.0 specification and supports high speed (480Mbps) and full speed (12Mbps) mode. The USB
interface is primarily used for AT command, data transmission, 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
9
IO
USB differential data bus (positive).
Require differential
impedance of 90Ω.
USB_DM
10
IO
USB differential data bus (minus).
Require differential
impedanc
e 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
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