Design and implementation of energy-efficient near-threshold standard cell library for IoT applications

Abstract

A CMOS standard cells library of low-energy, minimum-area, and fitted for IoT applications is introduced in this paper. The paper uses two solutions to provide significant energy saving. The first is to design the library to be operating in the Near-Threshold Voltage (NTV) region. The second is to create layouts of cells at the minimum possible area that can be achieved for a given technology process. To partially recover the speed loss due to operating in the NTV region, the pMOS performance is boosted by a proposed body biasing technique that connects pMOS body to the ground. Furthermore, minimum energy consumption is considered at the selection of the library supply voltage and the selection of each cell transistor sizing, while keeping the library performing in the range of 1 MHz up to 20 MHz. This range is sufficient for IoT applications. Another challenge for the NTV is Performance Sensitivity to the process variations, which is analyzed, then a design solution is provided to assure timing closure with such sensitivity. The UMC 130 nm CMOS process technology was used to design and characterize the proposed library. Library timing and physical views were created to enable its usage in both synthesis and physical design tools. Library benchmark was done on three cryptography algorithms to show the benefit for IoT applications. The used algorithms are AEGIS-128, ASCON, and AEZ. The maximum achieved frequency for these cores is 14 MHz, 18 MHz, and 16 MHz, and the corresponding energy consumption is 4.25 pJ, 10.03 pJ, and 30.57 pJ, respectively.