Can USB HS be used when VDD is 1V8 with an external ULPI PHY on STM32H750VBT6?

[jschloss]

I understand that VDD needs to be 3V3 if using the internal full speed transceiver, since STM32H750VBT6 has no VDDUSB input, but if I am using an external high speed USB ULPI PHY can the mcu be run at 1V8 and still use USB? I wan't quite able to figure out from the datasheet.

Thanks,

Jacob

[T J]

Q u i c k y guess ...... Yes.

approx 1.2-1.5V is the normal switching point so 1.8 is high...

which ULPI unit ?

[jschloss]

A TUSB1210BRHBR, http://www.ti.com/lit/ds/symlink/tusb1210.pdf

[T J]

on the ULPI,

Put VDDIO at 1.8V , and Vdd18

REF Clk at gnd, for an external clock input

on H7

VDD at 1.8V

[jschloss]

Ok Thanks!

[T J]

You will need low ESR Cap and extra caps..

you have no room to spike downwards, you need 10x capacity..( 0.1, 0.01, 1u 2.2u all caps)

You may need a 4layer board for the current spikes.