Incremental Delta-Sigma Structures for DC Measurement: an Overview

In this paper the theoretical operation of incremental (charge-balancing) delta-sigma (DeltaSigma) converters is reviewed, and the implementation of a 22-bit incremental A/D converter is described. Two different analyses of the first-order incremental converter are presented, and based on these results two extensions to higher-order modulators are proposed. Since line-frequency noise suppression is often important in measurement applications, modulators followed by sinc^k filters are also analyzed. Equations are derived for the estimation of the required number of cycles for a given resolution and architecture. Finally, the design and implementation of a third-order incremental converter with a fourth-order sine filter is briefly discussed