Running NUCLEOL433RC-P without external smps in stop mode.

[PSaxe.1]

Hi All,

I am working on a project which involves stm32l433RCT6P, LCD (4 x 28), GPIO, RTC and low power consumption.

I have finished developing whole applications and now working on exploring the low power modes of the mcu.

As per my recent findings, I have read in reference manual that MCU has 2 internal regulator viz. main regulator and low power internal. I am using HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);

to configure my controller in stop mode hence I am expecting the internal low power regulator to be turned on but unfortunately it appears to me that the MCU is still working on the external smps power. If I remove the JP8 jumper on the nucleo board then the core of the MCU stops.

Since I have failed to know the reason why the MCU always works with external smps only and also since I am on time crunch hence for time being I have made my mind to go for now with the external smps and hence I have made following changes to the nucleo board.

Please note that I have opened the jumper setting of PA4, PA5, PA6, PA7 since they collide with the my LCD controller pins. Instead I have made closed the SB85 and opened the SB84, so this should activate the smps by default when the jumper JP8 has been shorted. Also since I wont be needing the U10 i.e. multiplexer hence I have opened the SB30, SB46, SB39 and shorted the SB43. Doing so allows me to have the SMPS bypass the U10 mux and directly provide power on the VDD12 pin.

But since my device has to be cost effective hence I really want to remove the external SMPS dependency. Can someone please let me know if that is possible ? if yes then what may be reason why the MCU is not working on internal low power regulator.

Thank you.

[JCarl.3]

Hi,

Sorry I am a bit late to the party but it may help someone else.

It is possible to run the MCU without the external SMPS.

As you pointed out, you need to remove jumper JP8. This will remove the supply to the external SMPS which will remove voltage to the VDD12 pin. The MCU will detect this condition and will use its internal SMPS instead.

I assume you have been using the example project "PWR_STOP0_SMPS" for the NUCLEOL433RC-P. You may need to install System Workbench (SW4STM32) to compile the example project.

This is the crutial piece of information:

--> Make sure you comment out the call to function Enter_SMPS_Mode() as this will fail (stuck in an infinite loop). This is because it reads the POWER OK line from the SMPS which we have just disabled!

Also make sure macro DISABLE_SMPS is not defined.

You can setup your own project in STM32CubeIDE.

Make sure you import and call function IO_setting() in your own code before entering stop 0/2 mode to achieve the lowest current consumption.

Hope this helps.