A 0.018% THD+N, 88-dB PSRR PWM Class-D Amplifier for Direct Battery Hookup Y oungkil Choi,S t u d e n tM e m b e r ,I E E E, Wonho Tak, Y ounghyun Y oon, Jeongjin R oh, Senior Member , IEEE, Sunwoo Kwon,M e m b e r ,I E E E, and

Abstract

A low-distortion third-order class-D ampli fier that is fully integrated into a 0.18- mC M O Sp r o c e s sw a sd e s i g n e d for direct battery hookup in a m obile application. A class-D amplifier for direct battery hookup must have a suf ficiently high power supply rejection ratio (PSRR) in preparation for noise, such as when a global system for mobile communications (GSM) bursts ripples through the s ystem power line. This ampli fier has a high PSRR of 88 dB for 217-Hz power supply ripples, using a third-order loop filter. System performance and stability are improved by applying the design technique of input-feedforward delta-sigma modulators to the pulse-width modulation (PWM) class-D ampli fier. A filterless method that can remove the external LC filter is employed, which offers great advantages in terms of PCB space and system cost. This ampli fier achieves a power ef ficiency of 85.5% while delivering an output power of 750 mW into an 8- load from a 3.7-V supply voltage. Maximum achieved output power at 1% total harmonic distortion plus noise (THD+N) from a 4.9-V supply voltage into an 8- load is 1.15 W. This class-D ampli fier is designed to have a broad operational range of 2.7–4.9 V for the direct use of mobile phone battery power. It has a total area of 1.01 mm and achieves a THD+N of 0.018%.