A SAR ADC missing-decision level detection and removal technique

Abstract

Capacitor mismatch is the linearity limiter of charge redistribution SAR ADCs. This paper aims at detecting and removing the mismatch induced missing-decision levels (MDLs), i.e., large positive DNLs; these errors lead to information loss that cannot be recovered by external calibration. A switched-capacitor based approach is proposed to avoid DC currents and reduce design overhead; the hardware modification also supports comparator offset compensation to improve calibration quality. Simulation results show that the proposed technique effectively improves the SAR ADC linearity in the presence of capacitor mismatch and comparator offset.