A CJ-LMS hybrid calibration algorithm in SAR ADC

Abstract

In this paper, a Code-Jump (CJ) assisted Least Mean Square (LMS) calibration algorithm for high resolution successive approximation register (SAR) analog-to-digital converter (ADC) is proposed. This hybird algorithm does not require any specific input signal and has no impact on the ADC overall gain error. The revised LMS iteration algorithm is used to improve the accuracy of the lowest bits (LSBs) capacitor in the capacitive-digital-to-analog converter (CDAC), and the calibrated LSBs segment is used as reference capacitor to complete CJ calibration scheme. According to the results of 2000 Monte Carlo simulations, compared to the pre-calibration results, the hybrid CJ-LMS calibration method significantly improves the mean value of SNDR, increasing from 58.2dB to 70.6dB, while simultaneously reducing the sigma of the SNDR distribution from 3.1dB to 0.3dB.