Voltage reference buffer output does not match expected value?

[jugal]

Device: STM32G061 (custom board), system running at 8mhz.

I set the vrefbuf mode to Internal voltage reference mode in cubemx. According Scale 0 the expected output on Vref pin should be 2.048V but the value i measured was always 0.2-0.3V greater than expected. It is not constant, the value changes slightly after every power cycle. I see similar results for Scale 1 as well.

I have tried setting up the Vrefbuf through direct register access but without any luck.

VREFBUF->CSR |= VREFBUF_CSR_ENVR;   //internal voltage reference mode
VREFBUF->CSR &= ~VREFBUF_CSR_HIZ;   //Vref pin connected to vrefbuf output
while (!(VREFBUF->CSR & VREFBUF_CSR_VRR))  //wait for vref buf output to reach requested level

[TDK]

How are VREF+ and VDDA connected in your hardware?

[jugal]

VDDA and VREF+ are not connected to each other on my board.

[TDK]

Sure, but what are they connected to? A schematic would be the most informative.

[jugal]

VREF pin is not connected to anything. VDD has 2 bypass caps connected to it.

[TDK]

> VDD has 2 bypass caps connected to it.

Do you mean VDDA? So it's not connected to a voltage source? It should generally be connected to VDD. If that's not the problem, not sure what else it could be.

[jugal]

my micro does not have separate VDDA and VDD pin, and yes it is connected to 3.3V via VDD/VDDA pin.