Hybrid NEMS-CMOS DC-DC Converter for Improved Area and Power Efficiency

Abstract

Nano-electromechanical (NEM) relays are a promising class of emerging devices that exhibit zero leakage operation. Numerous end applications of NEM relay logic circuits have been proposed recently [1][2]. This work explores the usage of NEM relays in on-chip DC-DC converters. As a feasibility study of using NEMS in integrated power electronics, discontinuous conduction mode (DCM) buck regulator with specifications suitable for portable applications has been implemented in a NEMS-CMOS hybrid design and the results are compared against a standard commercial 0.35 μm CMOS implementation. Ron of the NEM relay switch is constant and is insensitive to the gate slew rate. This creates a paradigm shift in design of power switches. This coupled with infinite Roff offers significant area and power advantages over CMOS. Accurate Verilog-A models were developed based on published fabrication results of NEM relays [1] operating at 1V with a nominal air gap of 5-10nm. This work shows that NEMS-CMOS hybrid DC-DC converter has an area savings of 60V over CMOS and achieves 95% efficiency at max load condition (50mA).