Measurement of Digital Noise in MixedSignal 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 rms 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.