Capacitor value for Sigma-Delta ADC

Harley

Should the 1 nF (0.001 µF) value change if one runs with different sample bits number than example on AN001 page 17?

I'm working with a waveform in the low Hz range and wondered if a much slower rate would require a larger value.

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Harley Shanko

Phil Pilgrim (PhiPi)

These caps do not contribute much to the ADC's input time constant or frequency response. This is because, in theory, the voltage at the summing junction never changes; so there's virtually no capacitor charge/discharge occurring. As a consequence, I would stick with the recommended 1nF value.

-Phil

Harley

Thank you Phil,

Phil said...

These caps do not contribute much to the ADC's input time constant or frequency response. This is because, in theory, the voltage at the summing junction never changes; so there's virtually no capacitor charge/discharge occurring. As a consequence, I would stick with the recommended 1nF value.

In that case, I wonder why any need be used.

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Harley Shanko

Phil Pilgrim (PhiPi)

Noise abatement and to filter the feedback pulses.

-P.