CMOS multichannel sensor interface circuit using oversampled sigma-delta A-to-D conversion

Presents the design of a multichannel high-resolution analog-to-digital converter circuit with standard 2.5-μm CMOS technology. Instead of noisy analog multiplexers, digital multiplexing is achieved utilizing high-performance sigma-delta modulators. Due to the oversampling approach, no sample-and-hold circuitry is needed, and only a very simple analog antialias filtering is required. The one-bit-oversampled data includes quantization noise, which is out of the signal band and can be filtered out digitally. Two of the channels have high-resolution constraints, and they use low-order IIR filters and a simple decimation stage. The IIR filters use no general multipliers. The other two channels are mainly for estimation of spectral information of the signal. Therefore, an efficient linear-phase decimation filter is used to remove the quantization noise of the modulator. The resolution requirements in these channels are less than in the other two. The digital filters also work as antialiasing filters