I am using mk22fx512xxx12 controller, working on 3.3v.
System gets 5V as input, then in my board I have NOT used any isolation and converted it to 3.3V using LDO IC LP38690-3.3V also 12V is generated from 3.3V using dc to dc converter IC LMR61428.
This design works well as expected on table.
Now when taking EFT test (part of CE test) (in this we apply noise on power line ), my unit (which has analog and digital circuit) works well till 5 to 10 minutes Then suddenly MK22FX512xxx12 gets heated (very very hot) and draws current greater then 1.5A. Next if I replace controller with another on same system then system works ok.
I don't know why this is happening, this is repeated 3 times till now among 7 board we have assembled.
I find this interesting because we are using same controller on different products but i have NOT found same problem there.
What is problem in this design???
I have also repeated the tests by placing "toroid" at input of power supply on my board.
Any help from you people is highly appreciated....
Please feel free to ask any further inputs from my side, if any...