BG95-M3 unwanted Shutdown

I’m using a BG95-M3 modem and it presents an abnormal behavior - after a few seconds the modem shutdown.

  1. I developed a PCB to test and use the modem.
  2. I connected the TX + RX (main uart)+ GND pins to an STM32 develop board, and it ran properly
  3. Now I connect the TX + RX + GND pins to a PCB with an Arm Cortex M0 CPU, and the behavior starts to be abnormal :
    a) The modem has some time to respond to a few AT commands and then shutdowns, “NORMAL POWER DOWN” is received;
    b) The USB port is no longer recognized, and I can no longer use the QCOM tool;
    c) Connecting the modem with the STM32 the behavior is the same (shutdown).
    d) If I power up my Modem PCB with a Digital Power Supply it appears a short circuit indication.

The tests I executed:

  1. Continuity Test, I can’t figure out any short circuit.
  2. Evaluated the behavior of PWKEY, it’s correct
  3. Evaluated the power supply, VBAT_BB with 3.8V
  4. Evaluated the STATUS pin, after some time goes to 0 (shutdown). I also, see it in the led.

Can someone explain why is my Modem shutting down?

based on your description , your module seems to enter PSM mode ,

pls send the below at to check the status.



Thank you very much Stephen, it work.