Subthreshold to Above Threshold Level Shifter Design

While subthreshold operation, i.e., using a supply voltage below the transistor threshold voltage magnitude, has been suggested to achieve ultra-low power operation, widespread usage requires simple, reliable, and efficient circuits to interface to other voltage domains. In this paper, a level shifter circuit design that reliably translates voltages from circuits operating with VDD well below the transistor threshold voltage to voltages compatible with conventional CMOS designs is presented. The new low-power level shifter has been fabricated in a 0.13-mu m bulk CMOS technology. The design has been tested to operate with the low voltage logic supply as low as 100 mV driving circuits at 1.2 V, and can work above threshold without modification. The design is analyzed to show advantages over conventional, as well as comparator based level shifters.