ULPI integration on stm32 mcu clock reference

[nfranceschinis]

Hi everyone,

we are moving our design from usb full speed to usb high speed using STM32F76VI.

We want to use the suggested module STULPI01A in order to achieve this.

On datasheet is specified to use a precise reference clock.

Since our application use a gnss receiver which is quite sensitive we opted for using the PLLCLK routed out directly from MCU.

Is this system enough precise or are there any weakness in using this?

 

Thanks.

[nfranceschinis]

Ok, I add some informations about the design:

For the PHY clock we are using the STM32F7 output as suggested on MCU datasheet.

Our doubt was related on ULPI external clock source.

Actually for MCU we are using a 24 MHz oscillator connected to HSE input as main clock source.

The signal pass through the prescalers an arrive at MCO1 as PLLCLK where a divider made the MCO running at 26 MHz

We want to use the STM32 MCO output at 26 MHz to connect to ULPI ext clock source.

Is that enough?

 

 

[Gyessine]

hello @nfranceschinis 

For High-Speed operations, a stable and clean frequency of 48 MHz is required to ensure the PHY can reliably support HS mode.
BR,

Gyessine