An all-n-type dynamic adder for ultra-low-leakage IoT devices

Ultra-low leakage is demanded for low-duty-cycled IoT applications. An NP-type dynamic ripple-carry adder (NP-RCA) was shown outperforming the static design in terms of energy based on pre-layout simulations. We will show that the NP-RCA suffers from serious parasitic RC effects. We then propose an all-N-type RCA (All-N-RCA) in this work to reduce the influence of parasitic effects to achieve a much higher speed with a much lower leakage current. All the designs are evaluated according to post-layout simulation results in 28 nm CMOS. For an IoT application with a 0.02% duty cycle, the 32b All-N-RCA achieves a 57% energy reduction compared to the static counterpart at the typical process corner.