Mitigation of the sampling and substrate noise induced distortion in regenerative comparators by adaptive interpolation

This paper presents an interpolation filter scheme for regenerative comparators to suppress the induced sampling distortion resulting from the input-dependent timing error of the comparator´s sampling switches and furthermore alleviates the impact of random noise coupled from the substrate. The proposed scheme is based on the concept of charge-domain sampling and is realized by incorporating an active Miller integrator in the comparator. The integrator in conjunction with the sampling transistor makes each branch of the comparator a moving-average filter, which is effective for both deterministic and random signals. Moreover, the filter self-adjusts its transfer function according to the undesired signal´s frequency providing a more general and adaptive response. The effectiveness of the scheme is validated for both cases of interference on the comparator and the model is subsequently used to estimate the compensated SNR of a substrate-noise-affected flash converter.