Continuous-Time Delta-Sigma Modulator with SAR-Assisted Digital Noise Coupling

Continuous-time (CT) delta-sigma modulators (DSMs) are highly favored for their inherent anti-aliasing properties and ease of signal driving. However, their overall power consumption is often dominated by the static power of the opamps required in their analog loop filter (LF). Digital noise coupling (DNC) presents a compelling solution, providing additional noise shaping without the need for more analog integrators. DNC can also play a different role in CT multi-stage noise shaping (MASH) DSMs, where it is applied as noise leakage shaping rather than offering extra noise shaping. This review paper discusses detailed design motivations, followed by comparisons of various DNC variants. It includes design examples, supporting equations, and architectural enhancements. Potential trends for hybridizing DNC with other existing techniques are also introduced, providing designers with alternative strategies in CT DSM implementations.