Cannot enable SMPS STM32U385RGT6Q

[JVan .3]

The new version of CubeMx (6.15.0) nags me about enabling SMPS mode, and I would like to, but the tool seemingly does not have the capability to do so.

Under PWR->Low Power there's a checkbox for "Power Savings Mode" which other forum posts led me to believe would need to be enabled. I have found two things about this checkbox. 1.) It is already enabled and 2.) You cannot disable it.

Then, under "System Core" -> RCC ->Parameter Settings, there's a "Supply Source" parameter. It has only a "PWR_LDO_SUPPLY" option, and cannot be changed to any other value.

Am I missing something here, or is the tool broken?

[Imen.D]

Hello @JVan .3 

This is known issue reported in this post: STM32U3: Missing SMPS in power supply source, and escalated in the Internal ticket number: 214214.

This issue will be fixed in the coming release of CubeMX.

Thank you for your contributions.

[JVan .3]

Okay, great and thank you!

[ShawnLyu]

I also had this issue and hope to fix it soon!

[JVan .3]

Is this really the same issue? The other ticket you linked seems to be about the tool asking you to enable SMPS mode when it's not available. However, the STM32U385 does have SMPS mode, and the tool does not allow you to configure it on. I wound up turning it on like so:

  if(HAL_PWREx_ConfigSupply(PWR_SMPS_SUPPLY) != HAL_OK)
  {
    Error_Handler();
  }

And that seems to work fine.

[jerry65 · Accepted solution]

Hi JVan,

You're not missing anything — CubeMX 6.15.0 currently has a limitation or bug that prevents selecting PWR_SMPS_SUPPLY as the supply source for the STM32U385RGT6Q, even though the hardware supports it. The RCC supply source field is locked to PWR_LDO_SUPPLY, and there's no UI option to change it, which effectively blocks enabling SMPS via CubeMX.

The workaround right now is to manually configure the supply mode in your own code after CubeMX generates the project. You can use HAL_PWREx_ConfigSupply(PWR_SMPS_SUPPLY); early in main() or before clock config. Just make sure your power configuration and regulators are wired appropriately on your board (SMPS capacitor, voltage ranges, etc.) or it might cause startup failures.

ST likely needs to patch this in a future CubeMX update — report it if you haven’t already. Until then, CubeMX can’t fully configure SMPS mode for STM32U3 chips, and you’ll have to do it manually.

Regards