Anyone know how to disable the SMPS on STM32h757 when only using the LDO?

[TAtte.1]

My board implements this LDO use case from the user manual, no SMPS components and no SMPS circuit:

 

I need to enable this configuration:

However the device rejects ALL changes to these bits so the default configuration will not change to the LDO supply (or any other supply use case).

 

Service manual startup sequence has some clues:

Using my multimeter to probe the LDO output, I see 1.0 V but I cannot see 1.2V on the SMPS, because I don't have SMPS components installed on the board as per LDO use case above.

Is the PWR unit waiting for the SMPS 1.2V before permitting changes to the registers?

Any ideas greatly appreciated as I'm not sure if there is a simple work-around.

Service manual found here.

[KVan .2]

I have this same issue. Were able to find a solution?

[TAtte.1]

Reference manual is wrong. SMPS must be enabled or it won't boot. I needed to redesign my pcb to include the smps.

[KVan .2]

Okay thank you for the reply it looks like we might have to do the same.

[pema]

Hi @TAtte.1 I am also trying to use this MCU with the SMPS disabled.

Do you still think that the reference manual is wrong ? I already invested a 2nd PCB prototype on this and still cant get it to work.

Hi @KVan .2  did you manage to get it to work with the SMPS disable configuration ? Did you perform any extra configurations ?