Bi-Linear Homogeneity Enforced Calibration for Pipelined ADCs

TL;DR

This paper introduces the bi-linear homogeneity enforced calibration (BL-HEC) method for pipelined ADCs, enabling on-chip calibration by addressing inaccuracies in test signal scaling, supported by simulations and measurements.

Contribution

It proposes the BL-HEC approach to improve ADC calibration robustness and facilitate on-chip implementation by accounting for test signal scaling errors.

Findings

BL-HEC effectively compensates for test signal scaling inaccuracies.

The approach demonstrates stability in calibration procedures.

Experimental results validate the method on 24 integrated ADCs.

Abstract

Pipelined analog-to-digital converters (ADCs) are key enablers in many state-of-the-art signal processing systems with high sampling rates. In addition to high sampling rates, such systems often demand a high linearity. To meet these challenging linearity requirements, ADC calibration techniques were heavily investigated throughout the past decades. One limitation in ADC calibration is the need for a precisely known test signal. In our previous work, we proposed the homogeneity enforced calibration (HEC) approach, which circumvents this need by consecutively feeding a test signal and a scaled version of it into the ADC. The calibration itself is performed using only the corresponding output samples, such that the test signal can remain unknown. On the downside, the HEC approach requires to accurately scale the test signal, impeding an on-chip implementation. In this work, we provide a thorough analysis of the HEC approach, including limitations such as the effects of an inaccurately scaled test signal. Furthermore, the bi-linear homogeneity enforced calibration (BL-HEC) approach is introduced and suggested to account for an inaccurate scaling and, therefore, to facilitate an on-chip implementation. In addition, a comprehensive stability analysis of the BL-HEC approach is carried out. Finally, we verify our concept with behavioral Matlab simulations and measurements conducted on 24 integrated ADCs.