User's Guide

8
2.2.2. USB interface
2.2.2.1. Description
DWM-800A provides a high-speed USB interface by MINI PCI-E, which supports USB 2.0 protocol. The detailed
information is given in Table 2-2.
Table 2-2 DWM-800A USB interface description
Signals of
USB interface
The correlative pins in
MINI PCI-E
SN. of MINI PCI-E
Description
DM
USB_HS_DM
36
USB Data-
DP
USB_HS_DP
38
USB Data+
GND
GND
4,9,15,18,21,26,27,29,34,35,37,
43,50
GND
2.2.2.2. Reference circuit
The reference circuit of USB interface is shown in Figure 2-5 below.
1) To get the reliable USB power supply, it is recommended to use a 10uF（C406) filter capacitor and a 22pF（C407)
filter capacitor which need to be grounded.
2) To reduce the reflection caused by the high frequency alternating signal in the transmission, it is recommended to
add a resistor with value below 10Ω to the DM and DP in USB interface to ensure correct transmission for USB
data. Just like the resistors R408 and R409 in Figure 2-5.
3) To avoid static electricity in USB interface, it is recommended to use the ESD protection device. Just like the
varistor RV406, RV407 and RV408 with capacitor values below 3pF.
4) To ensure USB working reliably, it is recommended to use additional protection device.
Figure 2-5 The reference circuit of USB interface