A Digital Background Calibration Technique for Successive Approximation Register Analog-to-Digital Converter

Ling Du, Ning Ning, Shuangyi Wu, Qi Yu, Yang Liu

State Key Lab of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, China.
State Key Lab of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, China..

DOI: 10.4236/jcc.2013.16006                

Abstract

A digital background calibration technique that corrects the capacitor mismatches error is proposed for successive approximation register analog-to-digital converter (SAR ADC). The technique is implemented in SAR ADC which is based on tri-level switching. The termination capacitor in the Digital-to-Analog Converter (DAC) is regarded as a reference capacitor and the digital weights of all other unit capacitors are corrected with respect to the reference capacitor. To make a comparison between the size of the unit capacitor and that of the reference capacitor, each input sample is quantized twice. The unit capacitor being calibrated is swapped with the reference capacitor during the second conversion. The difference between the two conversion results is used to correct the digital weight of the unit capacitor under calibration. The calibration technique with two reference capacitors is presented to reduce the number of parameters to be estimated. Behavior simulation is performed to verify the proposed calibration technique by using a 12-bit SAR ADC with 3% random capacitor mismatch. The simulation results show that the Signal-to-Noise and Distortion Ratio (SNDR) is improved from 57.2 dB to 72.2 dB and the Spurious Free Dynamic Range (SFDR) is improved from 60.0 dB to 85.4 dB.

Keywords

Analog-to-Digital Conversion; Capacitor Mismatch; Digital Background Calibration; SAR ADC

Conflicts of Interest

The authors declare no conflicts of interest.

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