Heterogeneous NEMS-CMOS DCM Buck Regulator for Improved Area and Enhanced Power Efficiency

In CMOS switches, the input signal modulates the on-channel resistance for a constant gate voltage. This necessitates over design of CMOS switches. Also, further CMOS scaling in the nanometer regime has failed to improve energy efficiency due to increasing leakage energy. Looking beyond CMOS, nanoelectromechanical (NEM) relays are a promising class of emerging devices that exhibit energy-efficient switching and zero leakage operation. 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. Numerous end applications of NEM relay logic circuits have been proposed recently, including digital logic and memory. NEMS-based miniature switches form an interesting alternative in power management integrated circuits, the area of which is primarily dominated by CMOS power transistors. This study explores discontinuous-conduction mode buck regulator with specifications suitable for portable applications using a NEMS-CMOS hybrid design, and the results are compared against a standard commercial 0.35-μm CMOS implementation. The electromechanical model has been developed for a suspended gate relay operating at 1 V with a nominal air gap of 5-10 nm published in the literature. The model accounts for the mechanical, electrical, and dispersion effects in the relay. This study shows that NEMS-CMOS hybrid dc-dc converter has an area savings of 60% over CMOS and achieves an overall higher efficiency over CMOS, with a peak efficiency of 94.3% at 100 mA.