Power Nucleo from User USB

[dgiovanelli]

Hello,

as the title tells, I would like to power up a Nucleo 144 board (STM32l496) from its User USB connector. I've read the documentation and it tells that it is not possible, but would it remain impossible even with an external regulator connected to the USB VDD?

I tried taking the USB VDD power from the pin PA9, connect a step-down regulator and returning the regulated power to the 3.3 pin of the board but it doesn't work. If I boot the board power by STLINK and then I connect the User USB, on PA9 I see the 5V of the USB. But if is connect only the User USB (MCU is off), the PA9 pin never go to 5V.

Is this a kind of latch that, since the MCU is off, there are protection preventing PA9 to go higher than 0.3V, which makes the MCU to never startup? Are there any workaround to this?

Thank you,

Davide.

[TDK]

VBUS and PA9 are connected via a 10kOhm resistor. Not something you’re going to be able to draw power through.

If you connect VBUS (not PA9) to your voltage regulator, it should work, barring any other wiring issues.

[dgiovanelli]

Yes,you're right. I didn't noticed R54,I'll try to get the power before it!

[TDK]

Also the STM32I496 chip is not something that exists. Gotta be at least two typos in that one.

[dgiovanelli]

No typos,only a misleading lower case 'L'. It should be STM32L496..

[TDK]

Oops, I should have realized that.