A Monolithic CMOS 5V/1V Switched Capacitor DC-DC Step-down Converter

A 5V/1V Switched Capacitor DC-DC converter is designed and fabricated in a 0.35μm CMOS technology. The high side and low side driver circuits and control circuit for the converter are integrated. A folded cascode high speed CMOS operational amplifier is designed as an integral part of the control circuit. Test structures are fabricated as part of the main chip to validate simulation results and theoretical analysis. The switched capacitor topology and its operation are discussed in detail. The converter is designed to work at 25MHz switching frequency and achieve 5V to 1V power conversion. The use of small capacitors is made possible by higher frequency operation, thus enabling fabrication of capacitors on chip. The converter is simulated in Mentor-graphics analogue environment with AMS BSIM3v3 CMOS libraries over temperature and all process corners. The analytical solutions and simulation results are compared with the experiment results to validate the design. The design issues and layout issues of monolithic integration of switched capacitor DC-DC converters are discussed.