SELF-SUBTRACTIVE DITHERING IN HIGH-RESOLUTION SIGMA-DELTA A/D CONVERTERS

B. Jackiewicz

Abstract

An essential disadvantage of application of the oversapling sigma-delta A/D converters in high-resolution DC measuring systems are local peaks of quantization errors observed for some specific input signal values. The best method of elimination of those peaks is application of additional, deterministic, digitally generated dithering signal to the converter input. When averaging period of the converter digital output filter is a exact multiple of the period of the dither signal, this topology is intrinsically subtractive and elimination of DC residue is achieved without the need of additional digital subtraction. Experimental results of commercially available, nominally 24-bit sigma-delta converter with added simple self-subtractive circuit proved, that full elimination of the most significant peaks of errors was obtained. Increase of effective resolution of this converter (ENOB) was from 1,5 to 4 bits.

Keywords

Sigma-Delta A/D converter, oversampling, dithering

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IMEKO-WC-2000-EWADC-P627.pdf

DOI

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