Type-II Compensation for Automotive Buck Converters Implemented by Fully Integrated Capacitor Multiplier

Abstract

This paper presents a solution for full integration of a Type-II compensation circuit for DC-DC buck converters. It employs a novel active circuit based on capacitor multiplier, able to emulate the R-series-C ensemble within the conventional Gm-RC compensation network. The proposed solution was used to design a current-mode DC-DC buck converter for automotive applications. The implementation of key circuits in a 180 nm CMOS process is presented in some detail. Simulation results demonstrate that the converter meets all design requirements: it provides a 5 V output voltage over wide ranges of the input voltage, 6 V to 45 V, and load current, between 10 mA and 300 mA. Its frequency and transient responses compare well against the performance of a similar converter that employs a conventional Gm-RC compensation circuit. It consumes 20 $\mu \text{A}$ more, but requires significantly less die area, than its counterpart. Furthermore, the tuning required to compensate for process and temperature variations is realized by programming the multiplication factor of the capacitor multiplier.

Keywords

• Automotive
• buck converter
• capacitance multiplier
• fully integrated DC-DC converter
• type II compensation