A Variation-Tolerant Subthreshold to Superthreshold Level Shifter for Heterogeneous Interfaces

This brief presents a subthreshold to superthreshold level shifter (LS) for linking heterogeneous interfaces. As conventional LSs convert subthreshold signals to superthreshold ones, different device characteristics result in an imbalance of driving capability. However, process and temperature variations make the yield of LS much worse. With the proposed bootstrapping technique, this work not only eliminates tremendous imbalance of MOS driving capability but also reduces degradation due to process and temperature variations. According to Monte Carlo simulations, our design shows high concentration to driving current, delay time, and duty cycle. The delay variation coefficient is only 14%. Implemented in a 65-nm CMOS SPRVT process, the measured results show that our proposal shifts the voltage level from 0.2 to 1.0 V with an average of 12.9 ns delay time at 5 MHz. In addition, the measured delay time and duty cycle have high concentration even when temperature varies from -20°C to 120°C.