Voltage Scale 4 not possible with SDMMC for STM32U575ZITxQ, Cube MX, Low Level

[BSmit.7]

Hi,

I'm building a project using Cube MX (LL drivers) for the STM32U575ZITxQ processor (has SMPS) and I would like to get the processor into LL_PWR_REGU_VOLTAGE_SCALE4. Setting the MSIS to 16MHz achieves this but when I add in the 4 bit SDMMC interface in Cube MX the auto generated code only sets the regulator voltage to LL_PWR_REGU_VOLTAGE_SCALE3. This results in higher power consumption.

I am aware of the clock limitations of the SDMMC vs AHB bus and have adjusted PLL1P (sources SDMMC clock) to 16 MHz.

If I manually change the code to set it to SCALE 4 every thing seems to work ok but I would rather not deviate from the auto generated Cube MX code. Is it possible to achieve voltage scale 4 with SDMMC?

Many thanks

Ben

[Sara BEN HADJ YAHYA]

Hello @BSmit.7​ ,

Thanks for your feedback,

Could you please share your ioc file and specify the CubeMX version ?

Thanks,

Sara.

[BSmit.7]

Hi Sara,

Thanks for looking into this; Cube MX version 6.4.0.

The attached ioc file has:

• All modules set to LL in project manager
• MSIS set to 24MHz on the clock configuration
• the PLLM *N multiplier set to 16
• the PLL1P divider set to 8
• resulting in an SDMMC clock of 16 MHz
• SDMMC module disabled

Generating the code as-is for the ioc file will put the processor into LL_PWR_REGU_VOLTAGE_SCALE4 - line 124 of main.c for me.

If you enable the SDMMC1 in 4 bit mode this changes to LL_PWR_REGU_VOLTAGE_SCALE3

Many thanks

Ben

[Sara BEN HADJ YAHYA · Accepted solution]

Hello @BSmit.7​ ,

Actually this is a normal behavior, Range 4 is not allowed when using PLLs, HSI48 not divided by 2 or MSKI/MSIS having 48 MHz.

SDMMC uses either PLL1P or CLK48 as a source clock. In this case, Range 4 can be selected, when SDMMC uses CLK48 and CLK48 Clock Mux is set to MSIK.

PS: Adjust the frequencies according to your application and please make sure to enable LSE as it is required by the MSIK to calibrate itself.

I Hope this helps ��

If your issue is solved, please close this post by clicking the "Select as Best" button. This will help other members of the community find this response more quickly ��

Sara.

[BSmit.7]

Thanks Sara, that has sorted it!

Ben