A CMOS buck converter with PFM / hysteretic mode

Abstract

This paper proposes design of a CMOS DC-DC buck converter with Fixed Hysteretic mode and PFM(Pulse Frequency Modulation) mode. The inherent problems of a slow transient time from heavy load to light load that the conventional Dual DC-DC buck converters with PWM/PFM mode has faced have been resolved by using the proposed DC-DC buck converter which employed Hysteretic mode in heavy load. It improves transient time in load regulation. This also can maintain range of wide load current, advantage of Dual mode buck converter. The proposed Dual Buck Converter is fabricated in 180nm CMOS 1-poly 6-metal process and occupies a core effective area of 1.35 mm2. Measurement environment are input voltage range of 2.7∼3.3V, output voltage 1.2V and load current range from 10mA to 500mA. And measurement result shows that the maximum efficiency is 90% and ripple voltage is less 1.32mV.