STM32 fails to connect if AREF is not connected to VDD

[ferraridamiano]

Hi, I'm new in the STM32 world. I recently bougth the STM32L031K6 nucleo board and I am doing a project where I need to connect the analog reference to a voltage different from VDD. So I de-soldered the solder bridge that connects AREF to VDD (SB10). Now if I plug the cable in I get a fail file that says: "The interface firmware FAILED to reset/halt the target MCU" and the board doesn't work, if I connect vcc to aref all works good. What could it be?

Thank you all!

[TDK · Accepted solution]

VDDA must be connected to VDD. On this chip, VDDA is bonded to VREF+, so it must be connected to VDD.

[ferraridamiano]

Thank you! I've just read it on the datasheet. I have to change board🤦�?♂�?

[TDK]

Be aware there are also limits on VREF+, even if it's available as a separate pin. The same is true on other families as well.

[ferraridamiano]

Thanks!

I noticed that almost every stm32 board has Vref connected to VDDA. Do you know some that has this two pin separeted?