Hi Ö,
Could you tell me what the external crystal you are using? 8MHZ?
If yes, you can configure the PE like the following picture, and choose your USB clock source to the MCGPLLCLK, then the USB clock will be 48Mhz.


Wish it helps you!
If you still have question, please contact with me!
Have a great day,
Jingjing
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