Voltage-comparator-based measurement of equivalently sampled substrate noise waveforms in mixed-signal integrated circuits

This paper describes measurement of substrate noise waveforms in mixed-signal integrated circuits. This method uses wide-band chopper-type single-ended voltage comparators as on-chip noise detectors. By analyzing equivalently sampled comparator outputs in synchronized operation, the noise voltage in the auto-zero and compare modes can be measured separately, and noise waveforms were experimentally reconstructed to within 0.5-ns accuracy. The noise transmission path was analyzed, and this showed that the noise sampled at the auto-zero mode of the comparator can be used to reconstruct substrate noise waveforms with high resolution. The results also explain the influence of noise coupling on analog circuits widely used in on-chip analog-to-digital converters.