Does the Maximum Stable Amplitude depend on Reconstruction Filters in Incremental ∆Σ ADCs?

The maximum stable amplitude (MSA) is an important characteristic of a Delta-Sigma modulator (DSM) for high resolution and power efficiency. In free-running DSMs it is known that the MSA usually corresponds to a similar value as the amplitude with the maximum signal-to-quantization-noise ratio (SQNR) and that it depends on several factors including: loopfilter architecture, loopfilter scaling and aggressiveness, internal quantizer bit-width, signal transfer function (STF) and input frequency. Commonly, incremental Delta-Sigma (I-DS) analog-to-digital converters (ADCs) are derived from free-running prototypes enhanced by a periodic reset, and the assumption is that the underlying characteristics remain the same. In contrast, we elaborate in this work that the MSA of I-DS ADCs doesn’t correspond to the amplitude with the maximum SQNR anymore and that this amplitude is not exclusively determined by the DSM, but also depends on the chosen reconstruction filter. Furthermore, the reasons for this interdependency of the reconstruction filter and the amplitude with maximum SQNR are highlighted and solutions to solve this problem are presented.