STM32 Confusing users with description of Vref and VDDA

[JuM]

Hi,

in my opinion there is some confusion in description of VREFINT_CAL and VREFINT_DATA to determine VDDA.

My opinion: One determines VREF, not VDDA. One does not need to know VDDA in respect to measured values by ADC. One must know VREF (no matter if coming from extern via VREF+ pin or coming from intern e.g. 2.500V).

​What do you say ?

Juergen

[Tesla DeLorean]

Typically

VREF+ != VREFint

VREF+ == VDDA

[JuM]

Hi Clive, maybe you read my statement again...

I did not mix up reference voltage  for an ADC with VREF+ pin and/or VREFINT and/or VREFBUF.

Especially not mix up VREF+ with VREFINT.

One can use VREFINT and ADC_IN14 (and VDD_CALIB==3000mV) to determine the current reference voltage of the ADC.

The reference voltage, not VDDA.

This reference voltage may be VDDA (in case of the Nucleo Board this is the default case).

But if you switch to VREFBUF 2.500V as reference voltage you are no longer determining VDDA.

This should - my opinion - be written as such in Reference Manual of MCU.

Current text confuses newbies (as I was).

Juergen

[S.Ma]

Actually, on my side, I measure (after calibration) VDDA through Vref using calibration point (info is in the electrical parameters in the datasheet).

Once you know VddA, you can dig one more step and measure junction temperature (using other flash calibration point AND factoring out Vdda)