A 109-dB SFDR Continuous-Time Delta-Sigma Modulator for Audio Using Bi-Directional Advancing Data Weighted Averaging
A 109-dB SFDR Continuous-Time Delta-Sigma Modulator for Audio Using Bi-Directional Advancing Data Weighted Averaging
Abstract:
This brief presents a high-linearity third-order 3-bit continuous-time delta-sigma modulator (CTDSM) with 109 dB spurious-free dynamic range (SFDR) for audio applica-tions. The proposed modulator employs a cascade of integrators with feedforward structure using active RC integrators, a 3-bit flash quantizer, and resistor digital-to-analog converter (DAC) feedback. To address both DAC non-linearity and the tonal issues caused by conventional data weighted averaging (DWA), a new bi-directional advancing DWA (Bi-ADWA) with tone-suppressing and tone-transferring capabilities is introduced. Furthermore, the asymmetry in the rise/fall time of the DAC due to the additional paths introduced by Bi-ADWA is mitigated by optimizing the switch control circuitry and layout of the feedback DAC. Fabri-cated in a 180 nm CMOS technology, the modulator demonstrates a peak SNDR of 95.8 dB alongside a DR of 102.5 dB, consuming 0.58 mW at 1.8 V within an active area of 0.8 mm2 .
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A 109-dB SFDR Continuous-Time Delta-Sigma Modulator for Audio Using Bi-Directional Advancing Data Weighted Averaging
