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VDD33USB on STM32H743

Singh.Harjit
Senior II

The datasheet says that power must be supplied on this pin if USB is to be used. It must also be the last power supply to be energized and the first to be removed.

If my design does *not* use USB. Can I tie this pin to VSS and call it a day?

I want to minimize my power consumption.

From the datasheet: DS12110 Rev 5, Table 23:

Thank you.

4 REPLIES 4
Khouloud GARSI
Lead II

Hi @Singh.Harjit​ ,

I recommend to connect the VDD33USB pin to VDD. If you will not use USB (USB PHYs deactivated + related USB GPIOs (DM & DP) not used), this will not impact your power consumption.

Khouloud.

What if the VDD voltage is 1.8V ?

Connecting VDD33_USB to GND seems adequate according to the electrical specifications of the datasheet...

Thanks in advance for your answer

Stephane

Khouloud GARSI
Lead II

Hi Stephane,

It's recommended to connect the VDD33_USB to VDD even if your MCU is turning on 1.8V (USB peripheral will not be used).

The same voltage should be applied to VDD50_USB, in case the pin is available on the package you're using.

Khouloud.

BNord.1
Associate III

Hello ST Team,

I'm planning to use the USB communication with a STM32H743ZI. Then, I will have to use an external power supply, since it doesn't have VDD50USB input.

This MCU will be powered with a 3.3Vcc. power supply.

However, I read in the AN4938 (Getting started with STM32H74xI/G and STM32H75xI/G hardware development) the following statement:

"During the power-on and power-down phases (VDD < VDD minimum value),VDD33USB should always be lower than VDD".

If I connect directly the VDD33USB to the VDD, I won't be compliant with this recommendation. What would be the consequences during the power on/off? Is there a risk that the USB communication fails?

In any case, would there be a power management IC that would you suggest to use if I wanted to be compliant with this recommendation?

Thanks a lot for your help.