User Guide

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3.7.3 LED_WWAN# Signal
The LED_WWAN# signal interface is OC output format and the max current can reach up to the
40mA. When it connects to LED externally, connects the resistor in serial. You can adjust the LED
brightness by adjusting the resistance of resistor. When it is low, the external LED lights up.
Figure 8 shows the recommended circuit of the LED_WWAN# pin.
VCC
Figure 8 Driving Circuit
Check the LED_WWAN# signal network status indicator as below, when the M3B module is
successfully registered, the LED is on. When the RF is disabled, turned off or error (No SIM card
or registration failed), the LED is off.
Table 11 Network status indication
LED_WWAN# Description
Low Level（LED is on）
Successfully registered
High Impedance（LED is off）
1. No Internet or registration failed
1. W_DISABLE# pin is pulled down(disable RF)
LED_WWAN#
R
uCloudlink M3B Mini PCIe-C _Hardware Design Guide_V1.0