MCU stop working suddenly (LED driven by the MCU is off), can not be programmed anymore

[Jasmine]

Hi,

I use STM32H7A3LIH6Q in my project. Now we have two prototypes and I could program and run them at the beginning, LED is on or blinking.

Later when I started to test the DC/DC converter, both boards had LED (driven by MCU) off, and can not be programmed any more.

No smoke or smell happened.

The LED suddenly got off When I probe a test point (ITH pin of DC/DC converter) on DC/DC for the first board, and when I did load test to the 3.3 V rail for the second board. 

The power is ok, oscillator still works. The Vcore of the MCU is 1.3 V still, I’m wondering what could go wrong with the MCU, and since the MCU is not programmable at all, any thoughts to make it programmable again?

By the way, we use SWD, and those pins are designed for SWD. 

Any response is appreciated.

Jasmine

[Javier1]

show us pictures of your board, extra points if you include some altium/eagle snaps.

>>I’m wondering what could go wrong with the MCU

Gpio peripheral is dead or you didnt select SW pins as debugging in your code

• (try to connect to the mcu with stcubeprogrammer+stlink in Power down mode)

• As i believe you have an issue with your pcb layout, have you tried to power the board with a very low current limited power supply? and then with a thermal camera you could check out where is board building heat.

[Jasmine]

Thank you very much for the answer.

But I would like to say that my code works at the beginning, even I did power cycle, I have tested all the functionality I want.

It stop working when I measure ITH signal of DC/DC converter with multimeter. I'm sure probing this pin cause the issue. Because I reproduced it with the first batch by just probing this pin, and I see the LED off, the MCU can not be programmed any more.

With best wishes

Lijiao