4.2V Tolerant Buck Converter in a Standard 3.3V 0.13μm CMOS Technology

In this paper the design of integrated buck converters, tolerant to supply voltages higher than the process limit for individual CMOS transistors, is presented. In particular, the topologies for the level shifters and the power block are analyzed. Different driving solutions for a general circuit topology that use cascoded transistors in the output stage and can tolerate nearly twice the process voltage limit are discussed. A buck converter core incorporating an optimized usage of this power block and a modified version of a conventional voltage shifter was designed in a standard 3.3V, 0.13μm CMOS process. The converter is powered by a lithium-ion battery with a voltage range from 2.7V to 4.2V, and can deliver an output current up to 100mA with a programmable output voltage from 0.6V to 2.0V, with up to 90% efriciency. A methodology is presented for verification of high voltage compatibility of circuits design using low voltage technologies.