A study of asynchronous design methodology for robust CMOS-nano hybrid system design

Among the emerging alternatives to CMOS, molecular electronics based diode-resistor crossbar fabric has generated considerable interest in recent times. Logic circuit design with future nano-scale molecular devices using dense and regular crossbar fabrics is promising in terms of integration density, performance and power dissipation. However, circuit design using molecular switches involve some major challenges: 1) lack of voltage gain of these switches that prevents logic cascading; 2) large output voltage level degradation; 3) vulnerability to parameter variations that affect yield and robustness of operation; and 4) high defect rate. In this article, we analyze some of the above challenges and investigate the effectiveness of asynchronous design methodology in a hybrid system design platform using molecular crossbar and CMOS interfacing elements. We explore different approaches of asynchronous circuit design and compare their suitability in terms of several circuit design parameters. We then develop the methodology and an automated synthesis flow to support two different asynchronous design approaches ( Micropipelines and Four phase Dual-rail ) for system designs using nano-crossbar logic stages and CMOS interface data-storage elements. Circuit-level simulation results for several benchmarks show considerable advantage in terms of performance and robustness at moderate area and power overhead compared to two different synchronous implementations.