S32k118 ADC Accuracy

[종찬박]

Hi 

I compared actual voltage to ADC value.

but, those value were quite different.

I proceeded as follows.

could you tell me why calculating value is different with ADC value?

and do I have to what to check?

Regards,

Jongchan.

[Muskz]

Can I understand it this way? If I use an adc clock that is less than 4M, the maximum allowable rs for external circuits is 5k.
If I use an adc clock of 40M, what should be the rs? Why is it not stated in the manual, should it be larger or smaller than 5k?

Thank you.

[Robin_Shen · Accepted solution]

Hi Jongchan,

Please refer: AN12217, S32K1xx ADC guidelines, spec and configuration
The impedance of the analog signal source or series resistance (RIN) between the source and the input pin causes a voltage drop across it because of the current flowing into the pin. It can be understood as the resistance observed “looking out” of the ADC into the source driving the input signal to be sampled.

For this reason, precautions must be taken to ensure that the analog input signal source resistance is within ADC specification. In the datasheet for S32K devices, this parameter can be found as Source Impedance (RS).

Best Regards,
Robin
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