Measurement of digital noise in mixed-signal integrated circuits

This paper proposes a method of measuring the influence of digital noise on analog circuits using wide-band voltage comparators as noise detectors. Noise amplitude and r.m.s voltage are successfully measured by this method. A test chip is fabricated to measure the digital noise influence. From the experimental results, it is shown that the digital noise influence can be considerably reduced by using a differential configuration in analog circuits for mixed-signal IC's. The digital noise influence can be further reduced by lowering the digital supply voltage. These results show that the voltage-comparator-based measuring method is effective in measuring the influence of digital noise on analog circuits     

Voltage-comparator-based measurement of equivalently sampledsubstrate 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     

Substrate noise measurement by using noise-selective voltagecomparators in analog and digital mixed-signal integrated circuits

In mixed-signal integrated circuits (IC's), substrate noise produced by high-speed digital circuits passes to the on-chip analog circuits through the substrate and seriously degrades their performance. We have developed a method for measuring the substrate noise by using noise-selective chopper-type voltage comparators as noise detectors. This method can detect the wide-band substrate noise so we can analyze and further reduce its effect. A switched capacitance is selectively loaded on the output of the inverter amplifier of the comparator during the comparison period in order to reduce the noise detected at the transition from compare to auto-zero. In contrast, the noise at the transition from auto-zero to compare can be selectively detected. Waveforms of high-frequency substrate noise were reconstructed by using this on-chip-noise detector incorporating the noise-selective comparators implemented using a 0.5-μm CMOS bulk process