I have two boards connected to one another: the main board, which is responsible for charging, discharge, and battery monitoring of a pack, and the MCU board, which is responsible for communication and signals enabling and disabling various operations such as high voltage enable, battery voltage monitor, and so on. when I only used it to measure the battery voltage it was fine, when enabled the rest of the signals the boards started to consume over 700mA and the MCU got burned in the main boards there are serval protections and dc-dc convertors on the way to MCU.
I tested for shorts, signal contradictions ( inputs and outputs correctly ), and a current spike on both boards independently and didn't find anything.
connected a net of 1k resistor between MCU and the main to check for spikes and contradiction could not find any and they worked fine ( with the resisors). what else could be the cause and what test can I do?

 

Need schematics, board models, connection diagrams and good clear pictures to have any hope of providing good answers.

 

I understand however I cannot provide the images since its mostly confidential but il do my best to describe when it is stated to occur. the MCU circuit uses stm32g474met3 the issue started when I send from the microcontroller after started sending various signals such as high voltage enable to lm5060 and to fan enable signal feeds to mosfet gate

 

If you are unable to share enough information to allow us to help, I'm afraid you are on your own on this one!