Ultra low power high efficiency charge pump design using NEM relays

The zero leakage operation of Nano-electromechanical (NEM) relays make the device a promising candidate among emerging devices. Numerous end applications of NEM relay logic circuits have been proposed recently. This work explores the usage of NEM relays in on-chip power management circuits. R_on 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 R_off offers significant area and power advantages over CMOS. Accurate Verilog-A models were developed based on published fabrication results of NEM relays operating at 1V with a nominal air gap of 5 - 10nm. As a feasibility study of using NEMS in integrated power electronics, a step-down charge pump with specifications suitable for audio power amplifier applications has been implemented and the results are compared against a standard commercial 65nm CMOS implementation. This work shows that NEM relay based charge pump has an area savings of 73X, power savings of 14X over CMOS and achieves 96:1% efficiency at max load condition (18mA).