An LDO regulated DC-DC converter with voltage ripple suppression and adaptive dropout voltage control

Abstract

This paper presents a low dropout regulator (LDO) regulated DC-DC converter with suppressed voltage ripple and enhanced light load efficiency. In this proposed hybrid system, an adaptive dropout technique, where DC-DC converter takes the gate of LDO’s power transistor as the feedback point to combine DC-DC converter and LDO in one control loop, is adopted to make LDO’s dropout voltage adaptive to load current rather than fixed value. Owing to the cascaded LDO and the adaptive dropout technique, the hybrid system obtains a small voltage ripple with improved overall efficiency, especially in light load. The chip was implemented in 130 nm CMOS process. The voltage ripple is reduced to 3 mV at the load current of 40 mA. The overall efficiency of the proposed hybrid system is 60.74% in 30 mA light load and is improved by 15.6% compared with conventional fixed dropout voltage architecture.