A 470μW clock-free current-controlled class D amplifier with 0.02% THD+N and 82dB PSRR

This paper presents a clock-free current-controlled class D audio power amplifier. The proposed audio amplifier is based on integral sliding mode control (ISMC) to ensure system robustness and to provide zero steady-state error. The proposed audio amplifier´s hysteretic controller obviates the traditionally challenging triangle-wave carrier signal design task for pulse-width modulation (PWM). The IC prototype consumes at least 30% less static power than previously reported works and delivers 250mW of output power with 84% efficiency. The class D amplifier achieves up to 82dB of power supply rejection ratio (PSRR), more than 95dB of signal-to-noise ratio (SNR) over the entire audio band, and 0.02% of total harmonic distortion plus noise (THD+N). The audio amplifier was fabricated in 0.5μm CMOS standard technology, operates at 380kHz, and occupies 1.65mm².