A 16-bit Audio Continuous-Time Sigma-Delta Modulator Using VCO-based Quantizer

This paper presents a third-order continuous-time sigma-delta modulator for an audio application (16-bit dynamic range is targeted). It uses a multibit VCO-based quantizer to benefit from its properties: adding one noise-shaping order and mostly digital implementation saving power and area. Even if VCO linearity typically limits its application to medium resolution converters, using it as the last stage of a continuous time modulator allows to extend its application range even in high-resolution designs. For low-power issue, a second-order single-opamp loop filter is adopted as well as a tai-level DAC switching scheme with specific DWA. The design implemented in a 140nin standard CMOS technology reaches 98dB dynamic range in a 20kIlz bandwidth for a 142 mu W power consumption. This results in a Schreier FOM1 of 179.5dB which places the proposed modulator among the state-of-the-art designs.