A fully integrated soft switched high frequency resonant DC‐DC voltage regulator

Abstract

Fully integrated 750-MHz resonant voltage regulator is presented. Providing soft switching conditions for the transistors has prevented degradation of the converter efficiency at this high switching frequency. High switching frequency has reduced volume of the passive on-chip components and thus increased the converter current density. Due to the limitations of the CMOS processes, control and gate drive circuits are designed to increase chip reliability. One of the major challenges of the fully integrated voltage regulators is the on-chip inductor realization. Based on the mathematical models for inductance and resistance of spiral on-chip inductor, the geometric dimensions of the employed inductor are optimally designed to have maximum quality factor and minimum chip area. The power switches are optimized to achieve maximum efficiency. All post layout parasitic elements of MOSFETs and metal routings including inductive effects are extracted using 3-D EM simulation and finite element method for 0.18-μm standard CMOS technology. Maximum output voltage ripple is 5.2% at maximum load current. Peak efficiency of the proposed on-chip power supply is 82% when input/output voltage is 1.8 V/1.48 V and load current is 120 mA. Maximum value of the efficiency enhancement factor is 42% for output input/voltage of 1.8 V/0.55 V. Current density of the proposed converter is 574 mA/mm 2 . In the worst case, the load step causes an overvoltage/undervoltage smaller than 15.56% at the output voltage. K E Y W O R D Sfully integrated voltage regulator (FIVR), soft switching, resonant DC-DC buck converter, high current density, on-chip inductor optimum design