A Compact 31.47 fJ/Conversion Subthreshold Level Shifter with Wide Conversion Range in 65 nm MTCMOS

This paper presents an energy-efficient level shifter design that is capable of converting an extremely low input voltage to the supply voltage level. Featuring a core area as compact as 32.99μ² , the proposed design comprises a front-end current mirror and an output cross-coupled structure. Concretely, the current mirror is used to boost the complementary input signals to a proper level, with the operations of pull-up and pull-down networks well-balanced. The cross-coupled structure is used at the second stage to achieve a full-swing output. In addition, multi-threshold CMOS transistors are employed and optimized to elevate the circuit performance. The prototype was fabricated using a commercial 65-nm CMOS process. Experiments show that a 90-mV low input voltage can be successfully converted to 1.2 V. The energy consumed per conversion is reported to be 31.47 fJ for converting a 0.2-V input to 1.2 V at 10 MHz, and the corresponding propagation delay is measured to be 23.98 ns.