STM32U5 and USB HS

[dodotronic]

Hi all
I'm configuring STM32U5A5VJT to work with the USB HS crystaless. From the Cube it seems to be possibile to use one of the integrated oscillators as clock source for the USB HS but this is not mentioned in the datasheet.

I'm afraid that it could work but not in all the situations such as with high and low temperature.

Moreover in the STM32L4 I can use the 32768 crystal as calibrator for the internal oscillator that feeds the USB clock but in this case we are in USB FS while for U5 it's USB HS
My question is: Is the HSE crystal mandatory for USB HS?

[tjaekel]

As I understand the datasheet: for USB HS - you have to use a good external XTAL or CMOS OSC and use HSE as the clock source for USB. The internal HSE OSC (as an RC) is not stable and accurate enough (too much jitter and not the required ppm on clock deviation for USB).

[dodotronic]

ok thanks a lot!