URGENT due to PCB manufacfure - Can I use the STM32L433RCT6P without the external SMPS ?

[freeflyer]

I have designed a PCB that uses the STM32L433RCT6P which is the same processor used on the NUCLEO-L433RC-P board.

However, I am not using the external SMPS on the PCB I have designed.

I put up a post asking what I should do with the VDD12 pins if I dont use the external SMPS and was told to leave them floating (see https://community.st.com/t5/stm32-mcus-products/stm32l433rct-vdd12-pins-what-should-i-do-with-them/td-p/817459) so assumed I could use this MCU without the external SMPS.

My PCB is about to start production and now I am very concerned that the STM32L433RCT6P will not work without the external SMPS, is this true ? 

If so I need to cancel production asap so a quick answer would be greatly appreciated.

My schematic is below for reference...

If the STM32L433RCT6P can be used without the external SMPS, is there a setting somewhere to tell it to use the  internal LDO ?

During the design I did change to the non-P version (STM32L433RCT6) but I wanted to continue developing softwarea on the NUCLEO-L433RC-P board until my custom PCB arrived, so I reverted back to the STM32L433RCT6P

[TDK]

Yes, it will work. The chip boots up using the internal LDO. SMPS must be enabled.

Design recommendations for STM32L4xxxx with external SMPS, for ultra low power applications with high performance - Application note

Perhaps use your NUCLEO board to convince yourself of this.

VSS and VSSA must be tied.

[freeflyer]

Many thanks TDK, thats a big reliief :)

I have removed JP8 on the NUCLEO board and it appears to be working.

In fact I have been having difficulties flashing and debugging and I am wondering if it is because I reassigned the SMPS pins as follows....

• PA4
  • Was a digital output (SMPS_EN)
  • Now an analogue output (DAC1_OUT1)
• PA5
  • Was a digital output (SMPS_V1)
  • Still a digital output (STATUS_LED)
• PA6
  • Was a digital input (SMPS_PG)
  • Still a digital input (SPI MISO)
• PA7
  • Was a digital output (SMPS_SW)
  • Still a digital output (SPI MOSI)

Since removing JP8, I am now able to flash and debug, so I am wondering if reassigning these pins has damaged the SMPS ?

Link to post for reference...

https://community.st.com/t5/stm32-mcus-boards-and-hardware/nucleo-l433rc-p-board-difficulty-with-flashing-and-debugging/td-p/821934

[TDK]

Let's keep to one topic per thread (and one thread per topic), please. This keeps the forum more useful to others who may have similar issues in the future.

As a tip for getting more responses, try not to be the first to reply to your own thread. This makes it look like someone else has answered the question. Instead, edit your opening post if you need to add more details. Your other post has 3 replies, all by you, which make it look like someone has engaged so others may be less likely to look.