STM32 14-bit ADC: Extended vs. "normal" calibration procedure

[Uwe Bonnes]

Hello,

rm0456 in chapter 33.4.8. talks about "Software procedure to calibrate the ADC" and "Extended calibration mode" on some products. It is not clear, if "Software procedure to calibrate the ADC" is enough for products with "Extended calibration mode" or  if extended procedure should be done always when available?

Please clarify!

Thanks

[KDJEM.1]

Hello @Uwe Bonnes ;

First of all thank you for sharing this question in the community.

On STM32U5 there are different calibrations for ADC :

- The most common one "normal calibration mode" which calibrate the offset on the ADC and is depending on the device voltage.

- The extended mode is a linear calibration which improves the total harmonic distortion (THD) factor and then reduce the differential (ED) and integral (EL) linearity errors on the ADC. This feature requires more time to be active on the ADC than the normal calibration mode, but once activated it does not depend on the voltage, so you can avoid another calibration if the power voltage changes.

Both calibration are available on STM32U5 devices, and it is up to the customer to choose one or the other depending on the application.

Is my reply answer your question?

Thank you for your contribution in STCommunity.

Kaouthar

[Uwe Bonnes]

Thanks for the answer.  However now it is unclear if " linear calibration" in extended calibration includes the offset calibration from normal mode?

[KDJEM.1]

Hello @Uwe Bonnes ;

According to the datasheet; Offset calibration is not impacted by extended calibration mode.

Thank you.

Kaouthar

[KDJEM.1]

Hello @Uwe Bonnes ;

Any update?

Is my reply answered your initial question?

Thank you.

Kaouthar

[Uwe Bonnes]

Not really. Remark (2) from the datasheet cutout you show  tells: 

2. ADC DC accuracy values are measured after the internal calibration

but which of both possible calibrations is meant?

[KDJEM.1 · Accepted solution]

Hello @Uwe Bonnes ;

Concerning note 2. ADC DC accuracy values are measured after the internal calibration

Standard calibration for Rev. X

Extended calibration for other revision 

Thank you for your contribution in STCommunity.

Kaouthar

[Uwe Bonnes]

Clarification in the datasheet is welcome...

[KDJEM.1]

Hello @Uwe Bonnes ;

I reported your feedback internally.

Internal ticket number: 227107 (This is an internal tracking number and is not accessible or usable by customers).

Thank you.

Kaouthar