Short-Circuit Power Reduction by Using High-Threshold Transistors

In this brief paper, the dependency of short-circuit power on threshold voltage is analyzed and utilized for short circuit (SC) power reduction in multi-threshold (MTCMOS) processes. Analytical expressions are developed for estimation of the change of ratio between short-circuit power and dynamic power (PSC/Pdyn) while changing the design process. The analysis shows that the PSC/Pdyn ratio can increase significantly if the VT/Vdd ratio in new process decreases. An analytical expression is also derived for estimation of potential SC power reduction in MTCMOS processes by replacing low-VT transistors by high-VT devices in the same process. The proposed technique allows significant reduction of SC power without the need for process shift. The simulation results show good correlation with the analytical estimation at cell level, while demonstrating an average SC power saving of 36%. The performance impact is also validated, showing that timing degradation is minor and controllable. The proposed optimization technique is applicable to any multi-threshold process. The technique is simple for implementation, and can be easily integrated in the existing optimization tools.