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STM32L USB clock from HSI

Question asked by almeida.bruno on Sep 13, 2013
Latest reply on Apr 2, 2015 by ldim
I'm a little bit confused with clocking scheme of the USB peripheral in STM32L151.

On the datasheet, we see this affirmation, below the general clocking scheme of the microcontroller:

"For the USB function to be available, both HSE and PLL must be enabled, with the CPU running at either 24 MHz or 32 MHz."

But, on the user manual, there isn't the same advice, all that i found was the description of PLL on 5.2.4, which tell us that both HSI or HSE can supply the PLL, and that this is whom clock the usb.

My question is: Is it really necessary to have the HSE running to use USB peripheral, or HSI + PLL is enough?

Thanks in advance!