I'm trying to configure my custom board to only use the internal LDO, bypassing the need for the SMPS. In fact, my board doesn't even have the SMPS components. Is this allowed? The user manual seems to suggests that we can exclude the SMPS circuit however I can't configure the PWR_CR3 bits to turn off the SMPS.
My board is configured like this, as per the user manual:
On power on, the PWR_CR3 register shows the SMPS and LDO enabled by default. This is confirmed in the user manual as expected behavior which says the device can boot with either present. I can confirm that the system boots with just LDO but that's a far as I can go.
I've tried configuring the supply to disable the SMPS and to only use the LDO but that hasn't worked: HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY) does not work for me.
The SMPS and LDO bits in the PWR_CR3 register remain set.
LDO configuration on Page 277 of the manual says:
"The software has to program the supply configuration in PWR control register 3 (PWR_CR3). In addition, the VLXSMPS voltage level shall reach the programmed SDLEVEL so that ACTVOSRDY indicates valid voltage levels (see Figure 23)."
Two questions:
- How can the VLXSMPS voltage level reach the programmed SDLEVEL without the SMPS present?
- Why doesn't HAL_PWREx_ConfigSupply(PWR_LDO_SUPPLY) disable the SMPS bits?
