A gate-level leakage power reduction method for ultra-low-power CMOS circuits

In order to reduce the power dissipation of CMOS products, semiconductor manufacturers are reducing the power supply voltage. This requires that the transistor threshold voltages be reduced as well to maintain adequate performance and noise margins. However, this increases the subthreshold leakage current of p and n MOSFETs, which starts to offset the power savings obtained from power supply reduction. This problem will worsen in future generations of technology, as threshold voltages are reduced further. In order to overcome this, we propose a design technique that can be used during logic design in order to reduce the leakage current and power. We target designs where parts of the circuit are put in "standby" mode when not in use, which is becoming a common approach for low power design. The proposed design changes consist of minimal overhead circuitry that puts the circuit into a "low leakage standby state", whenever it goes into standby, and allows it to return to its original state when it is reactivated. We give an efficient algorithm for computing a good low leakage power state. We demonstrate this method on the ISCAS-89 benchmark suite and show leakage power reductions of up to 54% for some circuits.