Programming Strategies for Memristor Crossbar Arrays

This paper presents a comprehensive comparison of programming strategies for 1T1R (one transistor-one memristor) and 1S1R (one selector-one memristor) memristor crossbar arrays, focusing on unipolar and bipolar programming methods. The unipolar method utilizes a single power line (+Vdd) for both the word lines (WL) and bit lines (BL) terminals; while the bipolar method employs two power lines (+Vdd and -Vdd) exclusively for the WL terminal. These two programming strategies for 1T1R and 1S1R crossbar architectures are evaluated through simulations conducted in LTSPICE. Extensive results are presented in terms of operational features such as the NSP, output voltage, energy consumption, and delay. The simulation results show that the unipolar method not only consumes less energy but also supports programming in different directions; therefore, the advantages of unipolar method are better suited for neuromorphic computing applications when compared to bipolar voltage methods. Additionally, this paper evaluates the performance of 1T1R and 1S1R 2×2 crossbars under different programming with these two voltage methods. Simulation results show that under the unipolar voltage method, the 1T1R and 1S1R crossbars demonstrate lower energy consumption compared to the bipolar voltage method, while the unipolar voltage method can support programming from different directions. Therefore, the unipolar voltage method is better than bipolar voltage method for memristor crossbar.