Solutions of DC-DC converters for G-class audio amplifiers in mobile platforms

This paper presents a study and an analysis of the existing solutions for driving headphones in mobile platforms. solution converge to the use of G class audio amplifier. Such an amplifier requires a symmetrical power supply in order to get rid of huge external capacitors. Voltage scaling is mandatory in order to increase the system efficiency. The system is to be integrated into a mobile platform. The paper proposes to study three architectural solutions for the supply of such amplifiers. These architectures are benchmarked and discussed. The criterion taken into account for discrimination are the price and the footprint of external passives components, the silicon area, the number of IOs and the power efficiency. A single inductor, double output DC/DC converter is identified as an original and efficient candidate for this power supply. A primary prototype of the proposed architecture has been realized in a 130 nm CMOS process. The non-optimized testchip works in PWM in CCM and achieves 80% peak efficiency at 360 mW output power. Audio amplifiers are embedded on the same chip. The functionality of G class audio amplifiers supplied by this DC/DC converter is validated as well as the voltage scaling operation.