Design of a 20 MHz DC-DC Buck Converter with 84 Percent Efficiency for Portable Applications

Abstract

This paper presents the design and implementation of a 20 MHz voltage mode DC-DC buck converter with high power efficiency. The power efficiency has been improved by minimising the short circuit current in the driver stage. At the same time, a high gain, wide-band error amplifier topology with reduced current consumption, improves various dynamic performance parameters such as settling time, load and line regulations of the converter. A prototype of a 20 MHz DCDC buck converter is implemented and fabricated in 0.5 μm Bi-CMOS process with a maximum of 600 mA load current driving capability in the input voltage range of 2.7-5.5 V which is suitable for single-cell lithiumion (Li-Ion) battery operated portable applications. A reasonably good settling time of 10 μs is observed in the measured result with off-chip filter components of L=270 nH, C=1.6 μF. The measured value of load regulation and line regulation are 1.6 mV/A and 3 mV/V respectively. A maximum of 84% power efficiency is achieved at 2.7 V to 1.2 V conversion. A very low form factor of 2.5 mm × 2.5 mm × 0.7 mm, has been achieved by using power power flip-chip packaging technology.