Minimum leakage vector with sparse power gating – a combinational approach for standby leakage power reduction in CMOS circuits

Abstract

As silicon technology is scaling down, leakage power dissipation has become more significant among the all power dissipation mechanisms of complementary metal oxide semiconductor (CMOS) circuits. Minimum leakage vector (MLV) is a standby leakage power reduction technique for the combinational logic circuits. Though power gating is an excellent leakage power reduction technique compared to MLV standalone power gating technique has some inherent drawbacks like higher wake up time and circuit state loss. In this paper we combine MLV and power gating to achieve more leakage power reduction compared to MLV while mitigating the mentioned drawbacks of full circuit power gating. Instead of full circuit power gating, we developed a simple algorithm which runs in linear time to identify the gates with higher leakage power dissipation around which power gating can be carried out once combination logic is fed with its MLV. Flip flops and input ports of the circuit were modified to feed MLV in both standby mode and scan mode. Flop modifications also facilitate for partial power gating within the flops in standby mode while the states of flops are preserved to retain the state as circuit switches back to active mode. Our proposed combinational approach was tested with four selected ISCAS89 benchmarks using fast HSPICE simulations and achieved 30%-45% additional standby leakage power reduction compared to standalone MLV implemented with blocking logic with a maximum of 5% additional area trade off.