A DEM-Free Sturdy MASH Delta-Sigma Modulator with a Highly-Linear Tri-level DAC

Multi-stage noise shaping (MASH) Delta-Sigma modulators (DSMs) can achieve high-order noise shaping with single-bit quantizers, but they require high opamp gain for precise matching between the analog and the digital filters. The Sturdy MASH (SMASH) DSM relaxes the opamp gain requirement but multi-bit digital-to-analog converters (DACs) become necessary. The SMASH structure thus loses the inherent linearity arisen from the 1-bit DACs in the MASH structure, and often employ a dynamic element matching (DEM) scheme, which imposes a speed limit to the modulator. This work presents a DEM-free SMASH DSM by employing an inherently linear 3-level DAC in the first stage, which combines the advantages of both the MASH and SMASH structures. Simulations results are presented, validating the proposed architecture.