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

A method is proposed for measuring substrate noise waveforms in mixed-signal integrated circuits. This method uses wideband chopper-type single-ended voltage comparators as on-chip noise detectors. By analyzing the equivalently sampled comparator outputs from synchronized operation, the noise voltages in auto-zero and compare modes can be separately detected and the noise waveforms can be reconstructed within 2-nsec accuracy. The measured results also explain the influence of noise coupling on analog circuits widely used in on-chip analog to digital converters.