An energy-efficient subthreshold level shifter with a wide input voltage range

The level shifters are crucial primitives in the multi-supply voltage circuits and systems. In this paper, an energy-efficient level shifter is proposed to achieve the conversion from the subthreshold voltage to the above threshold voltage. It is a hybrid structure consisting of the Wilson current mirror and the cross-coupled level shifter. By addressing the voltage drop issue of the level shifter based on the Wilson current mirror, the leakage power is significantly reduced, with the advantage of wide input voltage range for the Wilson current mirror level shifter well-preserved. In addition, the multi-threshold CMOS (MTCMOS) technology is employed to provide more flexibility for our ultra-low power design. The reported simulation results using 65 nm CMOS process validate our proposed implementation and an ultra-low power consumption of 19.44 fJ per conversion from 0.2 V to 1.2 V at 1 MHz is achieved without the need of any intermediate power supply.

I. Introduction

The design concern on maximizing the performance while minimizing the power consumption has become more and more critical not only in the mobile consumer electronics but also in the wired embedded systems and high-end computing platforms [1], [2]. In [1], multi-supply-voltage implementation has been proven an effective solution to lower the power consumption, and the implementation capable of near-threshold and subthreshold operations have been proposed to provide optimal energy consumption [2]. However, sufficient driving strength for large capacitance of the interfaces or IO pads requires normal supply voltage for the related transistors (e.g. 1.8 V). Therefore, the level shifters are always inevitable for the conversion between different voltages.