On the design of a 2-2-0 MASH delta-sigma-pipeline modulator

In this paper, a 2-2-0 MASH delta-sigma modulator is presented. This architecture consists of two single-bit second-order delta-sigma modulators in the first and second stages and a pipeline ADC in the last stage. In the conventional cascaded delta-sigma-pipeline modulators, consisting of a single-loop delta-sigma modulator at the first stage and a pipeline ADC at the second stage, in order to achieve higher order noise shaping and stability of the modulator simultaneously, multi-bit quantizer and multi-bit DAC must be used, which cause the DAC non-linearity problem. Implementation of the cascaded delta-sigma-pipeline structure on a single bit 2-2 MASH delta-sigma modulator is proposed in this work and its advantages and disadvantages are considered in detail. The key feature of the proposed modulator is taking the advantages of 2-2 MASH delta-sigma modulator compared to other conventional cascaded delta-sigma-pipeline modulators. This architecture offers the possibility of implementation of a power efficient, fourth-order cascaded delta-sigma-pipeline modulator without having the stability or DAC non-linearity problems. The mismatch between the digital and analog filters in the pipeline part is also shaped by the order of two and therefore its hazardous effects are reduced. The system level simulation using MATLAB/SIMULINK confirms the usefulness of the presented structure.