Design and Characterization of Standard Cell Libraries for Optimal Subthreshold Circuits

Subthreshold operation is proved to be one of the most attractive approaches to achieve low power consumption with the trade-off in performance. Sizing of short channel devices operated in subthreshold region is very important for optimum power and performance of digital circuits. In this paper, the impact of Reverse Short Channel Effect (RCSE) and Inverse Narrow Width Effect (INWE) on the device I-V characteristics under subthreshold region is studied. Standard cell library suitable for subthreshold circuits by choosing optimum device sizing to achieve low power and high drive current by utilizing RSCE and INWE aware has been designed. The performance analysis and comparison of these two standard cell library-based circuits have been carried out. The standard cell library using conventional device sizing is also included for comparison. All the standard cell library design and characterization has been carried out using CADENCE LIBERATE tool. All the circuits are designed in VIRTUSO using 90nm CMOS technology from UMC. An 8-bit booth multiplier has been used as a benchmark circuit and synthesized using all the three standard cell libraries. Simulation results show that the multiplier synthesized using INWE based standard cell library has achieved 8.53% lesser power and 17.53% lesser area when compared to conventional sizing based standard cell library. Simultaneously, multiplier synthesized using RCSE aware standard cell library has achieved 15.2% lesser delay when compared to conventional sizing based standard cell library multiplier.