A Novel Energy-Efficient Sinusoidal Power Clocking-Based Writing Circuitry for the Hybrid CMOS/MTJ Architecture

Abstract

Spin transfer torque magnetic random access memory (STT-MRAM) offers a promising solution for low-power and high-density memory due to its compatibility with CMOS, higher density, scalable nature, and non-volatility. However, the higher energy required to write bit cells has remained a key challenge for its adaptation into battery-operated smart handheld devices. The existing low-energy writing solutions require additional complex control logic mechanisms, further constraining the available area. In this research, we propose a solution to design energy-efficient write circuits by incorporating two techniques together. First, we propose the sinusoidal power clocking mechanism replacing the DC power supply in the conventional CMOS design. Second, we propose three lookup table (LUT)-based control logic circuits and one write circuit to reduce the area and further minimize energy dissipation. The experimental results are verified over the case study implementations of $4 \times 4$ STT-MRAM macro designed using bit cell configurations: i) one transistor and one magnetic tunnel junction (MTJ) (1T-1MTJ) and ii) four transistors and two MTJs (4T-2MTJ). The post-layout simulation for the frequency range from 250 kHz to 6.25 MHz shows that the write circuit, which uses the proposed LUT-based control logic circuits and a write driver with a sinusoidal power supply, achieves more than a 65.05% average energy saving compared to the CMOS counterpart. Furthermore, the write circuit, which uses the proposed 6T write driver with the sinusoidal power supply, shows an improvement in energy saving by more than 70.60% compared to the CMOS counterpart. We also verified that the energy-saving performance remains relatively consistent with the change in temperature and the tunneling magnetoresistance (TMR) ratio.