A DLL Based Multiphase Hysteretic DC-DC Converter

Pengfei Li and Rizwan Bashirullah
University of Florida


Near-load DC-DC converter insertion based on multiphase current-sharing topologies and hysteretic control techniques can be used to reduce external current requirements, decrease the size of on-die capacitance and output filter and provide fast load response to enable multiple supply domains in future microprocessor platforms. In this paper, a new delay locked loop (DLL) based multiphase hysteretic controller is presented. This topology utilizes the switching frequency from one hysteretic controller to automatically synchronize the remaining phases and eliminate the need for external synchronization. A dedicated duty cycle control loop is used to enable current sharing and ripple cancellation. A four phase buck converter is designed with this control scheme in 0.6micron CMOS technology. Preliminary results show that less than 0.001 duty cycle resolution can be achieved for nearly equal current sharing among all phases and low output ripple. The proposed DLL based controller measures roughly 1.1mm by 0.4mm and dissipates approximately 40mW at 60MHz.