Comprehensive Background Calibration of Time-Interleaved Analog-to-Digital Converters

Abstract

A dynamic path-mismatch calibration operating on direct derivative information (DDI) augments the reference-path equalization technique of that treats static mismatch errors in time-interleaved (TI) analog-to-digital converters (ADC). The approach results in a comprehensive background calibration of interleaved ADC arrays suitable for digitizing wideband inputs. The DDI of the analog input is produced by a passive high-pass filter (HPF) followed by a zero-crossing comparator, and subsequently utilized in the process to extract the dynamic mismatch profiles of the TI conversion paths, i.e., timing skew, bandwidth mismatch, etc. A zero-forcing algorithm drives the adaptive tuning procedures of the converter front-end circuits to eliminate the mismatch errors at source. The non-idealities of the DDI circuitry and their impact on the calibration performance are discussed. Behavioral simulation of an 8-bit, 20-GS/s TI-ADC reveals that signal-to-noise plus distortion ratio (SNDR) and spurious-free dynamic range (SFDR) over 47 dB and 70 dB, respectively, can be routinely obtained for single-tone inputs from DC to Nyquist after calibration, demonstrating the efficacy of the proposed technique.