A high-frequency DC-DC converter based power amplifier for direct RF carrier generation

This paper describes the design and implementation of a high frequency DC-DC converter to directly generate an RF carrier for inductively coupled links in the 6.78 MHz industrial, scientific and medical (ISM) band. The proposed converter topology can also be utilized to dynamically adjust the power supply to improve system efficiency in RF power amplifiers. The DC-DC converter design is based on a delay-locked loop (DLL) synchronization scheme for high-frequency hysteretic controlled multiphase converters. The DLL control loop employs the switching frequency from a hysteretic comparator to automatically synchronize the remaining phases. We demonstrate a 25-70 MHz 4-phase converter with fast hysteretic control and output conversion range of 17%-80% while achieving a peak efficiency of 83% and peak-to-peak ripple within 10% in standard 0.5 mum 5V CMOS process.