I use the LM63635-Q1 to convert 15V to 5V.
I have a weird behaviour with a few boards. Sometimes the 5V doesn't start, no switching. 5V increases slowly to 0.985 V and stays at this value ( as if the IC if supplying the 5V via FB).
The fault is rare: maybe 1 out of 30 power-up.
Also the switching frequency is 315khz ( datasheet says 360 to 440 k).
When fault happens , Vcc is ok(5V)