Custom board help required . BG95-M3 boot-up issue

IoT Modules LPWA Module
1

Hi
I have a custom board with BG95-M3. The device powers on. I have verified with oscilloscope that VBAT is stable at 3.9V.
I have also checked that after the transistor the Voltage on PWR KEY is 1.5V stable.

I have tested on two boards.
When power is applied the Status LED turns on and off with approximately 3 seconds cycle. The module draws about 65mA , then 280mA , then 65mA then 280mA. This corresponds to the STATUS LED cycle.
I ahve checked all other signals like VEXT that remains stable at 1.8V and USBBOOT that it at 0V and PWR TRIG that is also 0V

I am not sure what is going on. Is the module powering on by it self and then going into a reboot cycle?

Thanks

2

I have held the host microcontroller in reset state so it is not interfering with BG95. Then force enabled the BG95 LDO and used a button to turn it on via PWR KEY. Still it drains 250mA and reboots continuously.

3

Have you checked RESET PIN and which power supply did you used?

4

I had the exact same behaviour on a custom board with BG95M2 and the problem was on the SIM card interface. The tvs diode array was rotated 180°. If you have 0 ohm resistors on the USIM pins, try removing them and see if it boots normally.

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5

Thanks Simon this is it!!!
You have saved so much time and effort! Thank you, I owe you one!!

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