A Delay Locked Loop Synchronization Scheme for High Frequency Multiphase Hysteretic DC-DC Converters

This paper reports a delay locked loop (DLL) based hysteretic controller for high-frequency multiphase buck DC-DC converters. The DLL control loop employs the switching frequency from a hysteretic comparator to automatically synchronize the remaining phases. A dedicated duty cycle control loop is used to enable current sharing and ripple cancellation. 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 0.6 mum 5 V CMOS process.