I can not get a VRef value with a STM32L082 (CMWX1ZZABZ-091)

[julius_21]

I'm working with a STM32L082 (CMWX1ZZABZ-091) and I can not get an accurate value of VRef (ADC_IN17).

This is important because the device is battery powered.

I am using the VREFINT_CAL (0x1FF8 0078 - 0x1FF8 0079) but there is an error of about 100mV.

I have also noticed that I have to wait about 10 mseconds to have a more sensible value but the specifaction is less.

The ADC is working fine with the external inputs but I need this reference to get an absolute value.

Thanks in advance

[waclawek.jan]

Do you calibrate before using ADC?

Do you use an adequate sampling time?

Is the reference (VDDA/VREF+) stable enough?

JW