FinFET Variability and Near-threshold operation: Impact on Full Adders design using XOR Blocks

Abstract

Near threshold operation reaches good results to energy critical applications. However, it introduces a considerable degradation on delay. Moreover, considering nano-effects, circuits operating at near-threshold are more sensitive to process variability. This paper analysis 9 full adders built with internal blocks that contain different combinations of 3 XOR logic circuits operating with nominal and near-threshold voltages under process variability effects. The experiments adopt the 7nm FinFET ASAP technology. The near-threshold operation can reduce on 97% the maximum power consumption and 65% the total energy, with an impact of about 10 times on delay. Considering process variability impact on energy and delay, the near-threshold operation turns the circuits about 1.6 and 4 times more sensitive in the critical cases, respectively. Compared with traditional full adders, the proposed circuits can improve around 15% of the delay with similar power results. The results provide valuable data and show how the impact of variability and near-threshold operation are important factors that must be analyzed to design more robust and low power circuits.