A background calibration scheme for pipefined ADCs including non-linear operational amplifier gain and reference error correction

Abstract

This paper presents a background noninvasive true calibration technique to correct for nonidealities in pipelined analog-to-digital converters (ADCs). Pipelined ADC suffers from finite nonlinear gain in amplifiers, ratio mismatch in capacitors, and errors in voltage references. Most calibration schemes do not account for reference voltage errors or nonlinearity in amplifiers, which introduce severe distortion in pipelined ADCs designed in a deep-submicron and nanometer-scale digital CMOS process. The proposed digital calibration scheme uses an insignificant, low-speed, low-power, high-resolution sigma-delta ADC to estimate a set of digital error-correction parameters in background using an adaptive LMS algorithm. The technique is shown to correct all static errors within a single framework - finite amplifier gain, capacitor ratio mismatch, voltage reference errors and amplifier nonlinearity. The scheme is demonstrated for a 14-bit A/D converter intended for speeds higher than 100Msample/s.