I am a hardware designer of home appliances. I am doing tests of immunity to electrical fast transients (BURST) of a PCB. On board there is a microcontroller, switching power supply, relays and cables connected to other devices. During the test (at any level), the microcontroller goes to fault. Removing all I/O cables direct to other devices, the appliance works perfectly. If i approaching any cable (floating or not) near microcontroller during the test, the appliances turn off.
If i use ferrite on every cable, varistor on uC power supply, nothing changes.
What can i do??
Best regards