Hi mark19960,
Thanks for your question.
I’ll need some more information.
Can you provide the schematic of your board?
How is the board layout compared to the EVB? (Please provide a layout pdf if possible) Did you try swapping the MOSFET from the MP3428A EVB to your board? If so, how did it respond?
Component placement and trace width could be a factor in the MOSFET getting very hot.
Regards,
Cindy