Thank you for your answer.
I have observed the waveform by using GND spring. At that time, I observed 7.4V overshoot.
But this time, I connect the probe to TP2 of EVM for GND and TP3 of EVM for PH directly.
So the overshoot reduce to 6.84V.
I will attach the waveform.
(Please visit the site to view this file)
But my customer worries about the margin up until maxiumum rating.
They want information for making a decision that TPS54318 doesn't break in consideration of the temperature change, the part variation.