SampTA 2011 BACKGROUND CALIBRATION OF TIMING SKEW IN TIME-INTERLEAVED A/D CONVERTERS

This paper describes theoretical details of a calibration method that addresses the problem of timing skew in timeinterleaved A/D converters. The algorithm utilizes an extra ADC outside the main signal path to estimate cross correlations between each sub-channel and samples taken along the calibration ADC’s ideal timing grid. Using the cross correlations, an iterative algorithm adjusts the sampling time instants in the main signal path to maximize the converter’s signal-to-noise ratio. The proposed scheme was implemented in hardware and improved the signal-tonoise ratio of an experimental 5-bit, 12-GS/s ADC by about 12 dB for inputs near Nyquist. Keywords— A/D conversion, time-interleaving, background calibration, cross correlation