Looking for some verification on the effects of multiplexing Delta-Sigma ADCs like the AD719x series. My understanding is that multiplexing effectively reduces the bandwidth of a signal that may be acquired while allowing a wider bandwidth of noise to be aliased through. For instance, suppose I use the AD7190 at the maximum 4800SPS rate, with the Sinc4 filter, chopper disabled, and auto sequencing through 4 channels. My per channel data rate will be approximately 300SPS, thus allowing un-aliased acquisition of signals on each channel up to 150SPS. But the ADC filter response (sinc4) has a -3dB point of roughly 1100Hz (0.23 * 4800). Thus any noise or extraneous signals from 150Hz up to 1100Hz will be aliased through, pretty much unattenuated - less so at the higher frequencies. So to reject noise beyond 150Hz, I will need to add an input filter with a break frequency somewhat lower than 150Hz, depending on how much noise rejection is desired.
Any feedback appreciated.