I am facing am issue where external MOSFET starts to smoke when the voltage is reduced from overvoltage condition to normal operating voltage at full load, at no-load condition circuit works fine. The design requirement was as follows- normal operation at 24vdc, overload at 30vdc, max load current 7A. attaching schematic for your reference. Was there some problem with my MOSFET selection or any other components?
After a successful start up, when you raise the input voltage above OV level, LTC4367 switches off the FETs. The load keeps on drawing energy from the output caps and depletes them. Now, when you bring the input voltage back in valid window (less than Overvoltage Falling Threshold which is 28.5V)), there is a 28.5V Vds (OV falling voltage) across the FETs and they have to conduct load current + current to charge 9.4mF output cap. As per SOA curve of the MOSFET used in this design (page#5 of the datasheet), at 28.5V Vds, this FET can only conduct 7A for 1ms before it blows up. I think this is the reason your FETs are blowing up.
You will have to use a FET that can handle a Vds = OVf while conducting load current and charging the output caps.
Thanks, will adding inrush protection solve this problem as per datasheet page#15 of LTC4367, without changing MOSFET.