I have tried use another way to enable TPS5420 instead of using EN pin ( since when disable TPS5420 by pulling down EN pin, there is still around 1V output).
But even when Q16 is totally shut down( Gate voltage and source voltage are the same), there is still 1.5V at Vin pin and 1.9V at output.
Please let me know what is the solution for this problem.
Many thanks.