Design of ultra-low-leakage near-threshold dynamic circuits in nano CMOS for IoT applications

IoT edge devices demand ultra-low leakage for lowly duty-cycled applications. It is usually believed that the static near-threshold-voltage (near-Vt) CMOS circuit is the only circuit style that is suitable for designing devices to achieve low power, low leakage, medium performance, and high robustness against PVT variations. In this work, we show that the dynamic circuit can be even better than the static circuit under the same performance requirement. First, through a design example, we obtain basic design guidelines for near-Vt dynamic circuits. Second, based on the obtained design guidelines, we demonstrate how to design a dynamic circuit with active and standby operation modes using a 32b ripple carry adder (RCA). All designs are based on 28 nm CMOS technology. We also compare the active and leakage power consumptions of both types of circuits of the same performance. For an IoT application with a 0.02% duty cycle, the 32b dynamic RCA achieves a 35% energy reduction compared to the static counterpart.