An Auto Offset Calibration Method for High-resolution Continuous CMOS Comparators

High-precision, continuous analog comparators are widely used in signal detection, alarm protection, and other fields.An auto offset calibration method for high-resolution continuous CMOS comparators (CMPs) was proposed.On the basis of the first output of the short-input format CMP, calibration logic will select the proper routine to calculate the best fix trim bit.Two calibration codes are added and averaged to obtain the actual code.This mainly takes into account the fact that there may be a certain delay in comparator flipping, which leads to deviations from the optimal calibration code.This part of the search error can be counteracted by averaging the results of searching from low to high and from high to low.According to different design needs, different trim step sizes can be obtained by adjusting the relative ratio of the smallest calibratio N-channel metal-oxide-semiconductor (NMOS) to the main input pair.Circuit implementation is based on the 110 nm flash process with a 5 V IO device.Analysis and simulation results show that a less than 1 mV offset can be easily achieved, which is suitable for commercial use.The proposed auto offset calibration method does not increase current consumption and can be easily shifted to other advanced technology processes, which make it promising for future use.