Hi,

Multibit delta-sigma modulators offer significant advantages once the problem of DAC mismatch is solved somehow. However, the output is still a multibit stream. Sometimes, one has to design a chip and only 1 pin is provided to interface the PDM output of an analog chip with a digital chip which does all the decimation, filtering and processing of the output.

Is it possible to convert the multibit undecimated stream from a delta-sigma ADC into a 1-bit stream at the same clock rate, which retains the information about the signal band to an acceptable accuracy (say 3 dB-6 dB degradation in SNR within the signal band compared to the multibit stream)? I was trying to think if one could prefilter the multibit output (at the same clock rate) and feed it to a digital delta-sigma modulator to get a 1-bit stream at the same clock rate. If yes, then how can one do it and what are the things to watch out for? If not, then why not? Is there any fundamental bound from an information theoretic viewpoint?

Thanks
Vivek