Digital Compensation for Timing Mismatches in Interleaved ADCs

Abstract

This paper describes a digital method of reducing timing mismatch effects in time-interleaved ADCs used in ATE systems: we use cross-correlation among channel ADC outputs to detect channel timing skew, and make successive-approximation adjustments to our proposed linear-phase-digital delay filter to compensate for the timing skew. Simulation results validate the effectiveness of the proposed method. We found that using multitone input signals with cross-correlation of outputs provided a more robust way of detecting timing skew than using a singletone input signal. Since our proposed approach is fully digital, it is reliable, and suitable for fine CMOS implementation.

How the Author's Group Came Up with Ideas in Analog/Mixed-Signal Circuit and System Area

“…Then we came up with combining correlation method and fine-delay digital filter for its calibration (Fig. 26) [70].…”

Digital background calibration algorithm and its FPGA implementation for timing mismatch correction of time-interleaved ADC

“…On the other hand, N additions are required to compute ðy½2n þ i AE y½2n À iÞ and N À 2 additions are required to compute the summations in the first and the second terms. Considering the three additions in (16), 2N þ 1 additions are required in total. Therefore, N þ 4 multiplications, 2N þ 1 additions and no divisions are required to compute the algorithm, which provides a light burden and therefore ease the hardware implementation.…”

“…In some cases, error detection is done by a cross-correlation function and error correction by using a voltage controlled sampling switch [15]. In [16], multiple filters with different delays are used to produce different delays. Based on the detected error, the calibration algorithm switches to the desired delay filter.…”

Analog/mixed-signal circuit design in nano CMOS era

“…For example, we have proposed a digital self-calibration method for timing skew effects in a time-interleaved ADC (Fig. 3), where the timing skew is detected by cross-correlation calculation among channel ADC outputs and compensated by our proposed linear-phase delay digital filter [4]. Digital self-calibration can be classified into foreground calibration and background calibration.…”