Active-mode leakage reduction with data-retained power gating

Power gating is one of the most effective solutions available to reduce leakage power. However, power gating is not practically usable in an active mode due to the overheads of inrush current and data retention. In this work, we propose a data-retained power gating (DRPG) technique which enables power gating of flip-flops during active mode. More precisely, we combine clock gating and power gating techniques, with the flip-flops being power-gated during clock masked periods. We introduce a retention switch which retains data during the power gating. With the retention switch, correct logic states and functionalities are guaranteed without additional control circuitry. The proposed technique can achieve significant active-mode leakage reduction over conventional designs with small area and performance overheads. In studies with a 65nm foundry library and open-source benchmarks, DRPG achieves up to 25.7% active-mode leakage savings (11.8% savings on average) over conventional designs.