Low Leakage Optimization Techniques for Multi-threshold CMOS Circuits

Background: With the reducing size of the devices, the leakage power has also increased exponentially in the nano-scale CMOS devices. Several techniques have been devised so far to minimize the leakage power, among which, MTCMOS (power-gating) is the preferred one as it effectively minimizes the leakage power without any complexity in the circuit. However, the power-gating technique suffers from problems like transition noise and delay. In this paper, we proposed a new simple yet effective technique to minimize leakage power in MTCMOS circuits. Objective: The objective of the paper was to propose a new technique which effectively minimizes leakage power in nanoscale power-gated circuits with minimal delay, noise and area requirement so that it can well be implemented in high-speed low-power digital integrated circuits. Methods: A new power-gating structure has been proposed in this paper. The new proposed technique includes three parallel NMOS transistors with variable widths which are functional during the active mode to reduce the on-time delay. A PMOS footer with gate-bias is also connected in parallel with the NMOS footer transistors. The proposed technique has been verified through simulation in 45nm MTCMOS technology to implement a 32 bit adder circuit. Results: The proposed technique offers significant reduction in leakage power, reactivation noise and reactivation energy. The technique reduced the leakage power effectively at room temperature as well as higher temperatures. The reactivation noise produced by the proposed technique minimized by 98.7%, 64.8%, 62.07% and 24.47% as compared to the parallel transistor, variable-width, charge-recycling and the modified-charge recycling techniques respectively at room temperature.The reactivation energy of the proposed technique also minimized by 77.by 77.67%, 55.8%, 45.1%, and 18.32% with respect to the parallel transistor, variable-width, CR and Modified-CR techniques, respectively. Conclusion: The proposed technique offers significant reduction in leakage power, reactivation noise and reactivation energy. The technique reduces the leakage power effectively at room temperature as well as at higher temperatures. Since the delay and area overhead of the proposed structure is minimal, hence it can be easily implemented in high-speed low-power digital circuits.