Nonvolatile, Spin-Based, and Low-Power Inexact Full Adder Circuits for Computing-in-Memory Image Processing

Deep submicron conventional complementary metal oxide semiconductor (CMOS) technology is facing various issues such as high static power consumption due to the increasing leakage currents. In recent years, spin-based technologies like magnetic tunnel junctions (MTJ) have emerged and shown some fascinating features to overcome the aforesaid issues of CMOS technology. The hybrid MTJ/CMOS circuits offer low power consumption, nonvolatility, and high performance. This paper proposes two novel hybrid MTJ/CMOS approximate full-adder circuits (AXMA) for low power approximate computing-in-memory architectures. The proposed AXMAs offer low area, high sensing speed, considerable lower energy consumption, and the lowest power delay product (PDP) than the considered antecedent counterparts. The proposed AXMAs also introduce the advantage of full nonvolatility to the systems. This feature allows the system to be powered off during the idle modes in order to reduce the static power without the need for any retention parts or loss of data. Applications of the proposed AXMAs in digital image processing and their effect on the quality of images considering some relevant metrics like peak signal-to-noise ratio (PSNR) and mean structural similarity (MSSIM) are also investigated using the MATLAB software.