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FIBOCOM SU806 Series Hardware Guide
Page 30 of 79
Connector
VBUS
DM
DP
ID
GND
Module
USB_DM
USB_DP
USB_ID
USB_VBUS
1
uF
VBAT
DC-DC
GPIO
Figure 3-9 USB 2.0 reference design (with OTG function)
Note:
1) Please choose junction capacitor less than 1pF for ESD protection device of USB_DP/DM
2) USB_DP and USB_DM are high-speed differential signal. The highest transmission rate is
480Mbps. Please pay attention to the following requirements in PCB layout:
⚫
USB_DP and USB_DM signal cables are required to be parallel and equal in length (differential
cable length controlled within 2 mm), while the right-angle route shall be avoided, and
differential 90Ω impedance shall be controlled.
⚫
USB2.0 differential signal cable laid on the signal layer nearest to the ground, with well
grounded.
3) Please choose DC-DC that satisfy output is 5V when support OTG function.
Table 3-7 Length of USB differential signal line in module
Pin Name
Pin
Number
Length (mm)
Length Difference (DP-DM) mm
USB_DP
14
11.33134
0.40037
USB_DM
13
10.93097