31.1 An 82mW ΔΣ-Based Filter-Less Class-D Headphone Amplifier with -93dB THD+N, 113dB SNR and 93% Efficiency

True Wireless Stereo/True Wireless Active-Noise-Canceling (ANC) headphones require low-latency digital-input headphone drivers that consume the lowest possible power to maximize battery life while providing high-fidelity audio playback. Typical headphone drivers use Class-A/AB topologies, and to improve power efficiency, Class-G/H drivers with a ground-center operation are used at the expense of using external components to decouple the required extra supply rails [1–3]. Closed-loop Class-D speaker drivers have become popular [4–6], and filter-less configurations are common in the 1-to-3W output range [6]. Some of the challenges associated with a Class-D driver for headphone applications are to maintain high linearity and SNR for low-voltage supply rails while reducing quiescent power. This paper describes a digital input, 93% efficient, filter-less Class-D amplifier achieving 113dB SNR and -93dB THD+N while operating from a single 1.8V supply.