An Energy Efficient Level Shifter Capable of Logic Conversion From Sub-15 mV to 1.2 V

Abstract

We propose architectural advances in low voltage, energy efficient, level shifters. A write assist circuit is introduced,to support up-conversion of deep subthreshold inputs. We also present an approach to reduce the leakage current in split signal output stages. A prototype was created in a 130 nm bulk CMOS process, and some samples were successfully tested for input voltages as low as 5 mV. For 10 measured samples, the mean functional, minimum, input voltage was 31.1 mV. By applying body bias to selected NMOS transistors to compensate for process and mismatch variation, the measured mean minimum input voltage was lowered to 14.3 mV. The leakage reduction in the split control output driver reduces the driver leakage by a factor of 8. The designed level shifter was found to be energy efficient compared to published structures, it consumed an average of 25.9 fJ per conversion in post-layout simulations and the delay was measured to 21.08 ns at 300 mV input signals.