A Versatile Low Power Oversampled A/D Converter

This paper presents a versatile low power oversampled A/D converter that can be either configured as a sigma delta converter or an incremental converter. The latter refers to oversampled instrumentation converters that cancel offset and 1/f noise. Versatility is achieved by keeping the design completely modular and programmable. Indeed, the implemented converter has been built with a number of identical slices, each consisting of an analog modulator and a companion digital accumulator. Programmable options are : sigma delta or incremental mode, selection of modulator order between 1 and 4, choice of oversampling factor between 2**3 and 2**18, and a comb filter order setting between 1 and 5. The proposed architecture not only leads to simpler structures. It also permits a rapid tailoring of area-optimized A/D converters to given ASIC specifications. In incremental mode, a 16 bits resolution is achieved for DC input values with an integral non-linearity error of ±20 μV. Offset and even order harmonics are cancelled to non-observable levels. The power consumption is, in this mode, 20 μA on a supply of ±2 V.