Hello!
It's been a while since I'm working with STM32H7 MCUs and now, some of the products using it are returning from my customers, not working at all. Analyzing the board, I get a short circuit between 3V3 and GND and after removing the MCU, the short circuit is gone. Nothing more on board is damaged, so putting a new MCU solves the issue and than the product is returned to the customer.
I can't share the board schematic due confidential rules on my company but basically it's a 12VDC device with 3V3 and 5V regulators, 4 layers PCB. All MCU pins are in use and there are the following features:
- 1 QuadSPI (Serial flash memory)
- 1 SPI (EEPROM)
- 1 I2C (16x2 LCD)
- 1 CAN (ATA transceiver)
- 1 USB Host
- 6 UARTs (4 RS485 and 2 RS232 by transistor)
- 1 PWM output (Buzzer)
- GPIOs (8 relays, 5 push-buttons and general I/Os)
All genereal inputs have diode protection and the outputs are transistor based. The push-buttons active on GND, counting only with the internal pull-ups. CAN and RS485 have ESD protections and all pins were checked by 5V tolarance. The software is burned to internal and external flash using ST-LINK/V2.
So I'm kind of lost of what's causing this issue. The first thought was about ESD, as most of the customers told me that they just plugged the 12VDC power supply with nothing else connected to the board. But I don't think SMT32 is that sensitive...
Do you guys have any idea?
Thanks a lot!
