ADC differences at an STM32F071V8Tx

[albreco]

Hi,

we use 12 ADC channels to measure temperatures in a smart home project. The system clock of the STM32F071V8Tx is configured at 48 MHz. Due to the slow temperature curve, we use the longest sampling time. We have taken a conversion table from a data sheet of the controller, which contains which bit value of the ADC is supplied at which input voltage.
So at 1.74V 2082 tics should be delivered. However, the ADC only delivers 2159 tics. The difference of 23 tics is outside the tolerance specified by ST. The configuration can be seen in the following diagram.

The controller is operated with 3.3V, the reference voltage of the ADC corresponds to the operating voltage.
What could be the cause of this deviation?

 

[waclawek.jan]

Do you calibrate ADC before use, as outlined in the ADC chapter of Reference Manual?

JW