Marino De Jesus Guzman

This article presents a new structure of multi-loop continuous-time delta-sigma modulator (CTDSM) with voltage-controlled oscillator-based quantizer (VCO-Q) featuring a robust system with design flexibility and calibration-free. A recent work called correlated dual-loop (CDL) sturdy multi-stage noise-shaping (SMASH) delta-sigma modulator (DSM) removes the explicit quantization error extraction digital-to-analog converter (DAC) needed in conventional multi-loop structures. However, the limited design flexibility and the system’s robustness compromise the application of the CDL. The proposed structure is developed based on the core of the CDL SMASH and addresses its limitations by optimizing the noise transfer function (NTF) and introducing a distributed signal feed-in approach. Furthermore, the signal distribution can also constrain the input swing of the quantizers in our proposed structure. As a result, the VCO-Q, which is limited by nonlinearity issues, can be incorporated well into this design without extra calibration circuits. Fabricated in a 65-nm process, the prototype achieves a 77.2-dB dynamic range (DR) in a 15.625-MHz bandwidth at a 500-MHz sampling rate corresponding to a power consumption of 12.5 mW. The peak Walden figure of merits (FOM) of the proposed design is 97.66 fJ/conv-step with a signal-to-noise-and-distortion ratio (SNDR) of 74 dB.

This brief presents a more detailed model for the slewing behavior of self-biased ring amplifiers and outlines the factors which affect the large signal operation. A set of analytical expressions derived for the self-biased ring amplifier are presented which are valid for a larger portion of a design space than prior expressions. The equations presented are well matched with simulation results and the accuracy of the derived equations is reported. Finally, the paper examines the proposed equations and simulation results to provide insight about design parameter dependence.