S32K SAR ADC Input Circuit

[christhomas]

Hi,

Is the input RC circuit (RF and CF) necessary when interfacing to the analog inputs within the S32K processor. If instead the analog input is passed through a buffer and then straight to the MCU Analog pin, would that be ok as well or would that deteriote the performance/accuracy?

Also, if there is no capacitor between VREFH and VREFL, would that cause accuracy problems?

[jorge_a_vazquez]

Hi christhomas

The serial resistance affects the timing of charge the internal capacitor and so the timing of measuring the voltage, the user should assure that this resistance is inside the parameters of the datasheet.

Regarding the reference Voltage, they should be as stable and as high as possible within spec so any noise here could affect your measurements. VREFH means larger ADC code widths.

I recommend you the following Document:

https://www.nxp.com/docs/en/application-note/AN12217.pdf 

Have a great day,
TIC

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