A 1.8V 1.0GS/s 10b self-calibrating unified-folding-interpolating ADC with 9.1 ENOB at Nyquist frequency

An advance in folding-interpolating ADCs is presented that simplifies their extension to higher resolution by building the converter out of identical but scaled pipelined cascaded folding stages. The limitation of the classical folding architecture is the separate coarse channel to determine which fold an input signal is in. Higher-resolution ADCs benefit from a higher order of folding, which results in more closely spaced folds and makes the alignment between this "fine" channel and the "coarse" channel increasingly difficult due to offset and settling mismatch. In this paper we eliminate this separate coarse channel using instead a single "unified" set of cascaded folding stages, in which each folding stage acts as the coarse channel for the following folding stage. This extends previous work where the coarse channel is distributed and where the cascaded folding stages are pipelined. Our approach is demonstrated in a dual 1.8 V 1.0 GS/s 10 b ADC that achieves plusmn0.2 LSB DNL and 9.1 ENOB at Nyquist while consuming 1.2 W/channel.