B.Fan, You are correct that the filter (Cfilt and Rfilt) is to overcome the charge kickback (i.e. spiky response) from the ADC. However, this filter is not an anti-aliasing filter. Some literature refers to this filter as anti-aliasing, but that is actually incorrect. The reason that it will not work as an anti-aliasing filter is that in order to get good settling the cutoff of this filter is generally going to be higher than the Nyquist frequency. In the example you show, the cutoff of the filter is 1.98MHz and the maximum sampling rate for the ADS7042 is 1Msps (Nyquist = 500ksps). For the filter to be an effective anti-aliasing filter, it needs to have a cutoff lower that the Nyquist frequency. For example an effective anti-aliasing filter may be a second order filter with a 50kHz cutoff. This filter will have a 40dB attenuation at 500kHz so any alias signals will be significantly attenuated. I suggest looking at Anti-aliasing , and Anti-aliasing hands-on videos to understand this better. Thanks for your interest.
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