A Low-Power High-PSRR Clock-Free Current-Controlled Class-D Audio Ampli fier Joselyn Torres, Student Member , IEEE , Adrian Colli-Menchi , Student Member , IEEE

Abstract

A low power, high PSRR, clock-free, current-con- trolled class-D audio power ampli fier is presented. The proposed audio amplifier utilizes integral sliding mode control (ISMC) to en- sure robust operation and to minimize the steady-state error. This architecture has two feedback loops: an outer voltage loop that minimizes the voltage error between the input and output audio signals, and an inner current loop that measures the inductor cur- rent to track the input signal accurately. The proposed ampli fier achieves up to 82 dB of power supply rejection ratio (PSRR), more than 90 dB of signal-to-noise (SNR) ratio over the entire audio band, and total harmonic distortion plus noise (THD+N) as low as 0.02%. A power-supply-induced intermodulation distortion (PS-IMD) of approximately 90 dBc was measured for an input voltage signal of 2 at 1 kHz and a sinusoidal power-supply ripple of 300 mV at 217 Hz superimposed on the DC level. The IC prototype’s controller consumes 30% less power than those of recently published works. The audio ampli fier operates with a 2.7-V single voltage supply and d elivers a maximum output power of 410 mW with 84% peak ef ficiency ( )i n t oa n8 speaker. It was fabricated using 0.5 m CMOS standard technology, and occupies a total active area of 1.65 mm .