Design and performance analysis of Hybrid VCMA+STT-MTJ/CMOS circuits for CIM Architecture

The emerging computation-in-memory (CIM) architecture effectively overcomes the limitations, such as memory wall and rise in the standby power dissipation associated with the conventional von-Neumann structure. In this article, we developed hybrid voltage-controlled magnetic anisotropy-assisted spin-transfer torque magnetic tunnel junction (VCMA + STT MTJ) circuits for the CIM architecture. Initially, we have proposed a novel VCMA + STT MTJ write circuit that is 63.35% and 94.86% more energy efficient with 50.87% and 59.42% lower transistors compared to spin-Hall effect-assisted (SHE) MTJ STT and STT MTJs, respectively. Subsequently, development of VCMA + STT non-volatile full adder (NVFA) with the novel write circuit unravels its supremacy with 42.21% and 89.25% reduction in total power dissipation, 35.16% and 41% lower transistor count, 31.93% and 95.13% faster write speed, and 62.79% and 99.53% lesser write power delay product (PDP) compared with SHE + STT-NVFA and STT-NVFA, respectively. Using VCMA + STT-NVFA, we have developed a non-volatile (NV)-arithmetic logic unit (ALU) to perform addition, subtraction, and all the logic operations. Comparison of the same has been conducted with its CMOS counterpart to show that NV-ALU is better in terms of power dissipation, and transistor count by 12.12% and 15.71%, respectively. Furthermore, we have extended the NV-ALU for 4 bit operations to show its feasibility for higher bit operations.