ADC voltage reference selection (F7).

zupazt3 · ‎2017-05-16

Posted on May 16, 2017 at 18:50

Coming form AVR to STM32 F7 46, can I select voltage reference for ADC. Like in AVR, I could choose AVDD or VREF.

Besides,

If I connect 2.5V to the VREF and 3.3 to AVDD, then what is the range of ADC measurement?

1) Is ADC range from 0V to 2.5V?

2) Or is 2.5V used to calibrate ADC reference (AVDD) and then range will be from 0V to 3.3V (=calibrated AVDD)?

In AVR 1) is correct. How about here?

waclawek.jan · ‎2017-05-16

Posted on May 17, 2017 at 02:29

ADC measurement range is 0 to VREF+.

Only some of the largest packages have a separate VREF+ pin, the smaller packages have it connected to VDDA.

There are lmitations to the VREF+ to VDDA voltage difference, read datasheet.

The internal reference cannot be used as reference to ADC. Rather, it's a fixed voltage source connectable to one of the ADC mux intputs, to provide calibration to VREF+/VDDA if those are sourced from a lesser-stable regulator.

JW