STM32G431RBT6 ADC internal Vref 2.048V

[sshan.2]

Hi Team,

We are using STM32G431RBT6, we have tested the ADC1 for PA3 i.e. Channel4 with external Vref 3.3 and VDDA 3.3 with 12-bit selection and the reading we are getting with 5 to 10 counts fluctuations we are seeing but when we have changed to internal voltage ref selection for 2.048 then the PA3 i.e. Channel4 is fluctuating more than 1000 counts! but it works fine for PA0!

VDDA remains same 3.3v for both our internal and external voltage.

Please suggest us how to resolve this?? 

Thanks 

[sshan.2]

yes Vref+ pin is not connected any capacitors, but we can see 2.048 on multimeter.

can you please suggest right value of capacitor to connect?? or should follow the same as shown above image??

[sshan.2]

Hi Billy,

as we are struck at this point and please let us know which email ID, we need to send the query??

can we get instant chat support for this??

[Chris21]

As MasterT already said, if you are using a Nucleo board, PA3 is likely used for serial communication to the ST-LINK:

[TDK]

> or should follow the same as shown above image??

Yes. Or follow the reference design in the hardware guide.

https://www.st.com/resource/en/application_note/an5093-getting-started-with-stm32g4-series--hardware-development-boards-stmicroelectronics.pdf

[sshan.2]

Thanks, team 

I have added and got results with no fluctuations and I also referred the AN5093 Application note