User Guide

23／35
Figure 6 Recommended Circuit of USB Interface
In order to meet the requirement for completeness of USB signal trace, R1 and R2 shall be placed
near the M3B module and ESD protection components.
Based on the USB 2.0 specification, please comply with the following requirements:
1. It is required to control the differential impendence -90ohm.
2. Do not route the USB signal trace under the following components: crystals, oscillator,
electromagnetic component and RF signal. Keep it away from interference sources and signals
susceptible to disturbance and shielding with ground.
3. If the USB interface of the M2 module is connected to the USB socket, place ESD protection
component with no more than of 2pF capacitance near the USB socket.
4. Avoid the coupled noise on the USB signal trace, keep the testing stubs as short as possible. If
possible, add resistor of 0 ohm or common mode choke to the USB signal trace.
3.7 Signal Control Signal
Table 9 lists the pins on the signal control interface.
Table 9 Definition of the pins on the signal control interface
Pin No.
Pin Name
Pad Type Typ.(V) Description
20 W_DISABLE# DI 1.8V
Disable RF communication, effective
low level (inside pull up)
22, 33 PERST# DI 1.8V
Reset control, low level reset (internal
pull up)
42 LED_WWAN# OC — Status Indication
USB_DP
USB_DM
GND
USB_DP
USB_DM
GND
R1
R2
Close to Module
ESD Array
R 0
0 R
Module
MCU
uCloudlink M3B Mini PCIe-C _Hardware Design Guide_V1.0