A Combined Gate Replacement and Input Vector Control Approach for Leakage Current Reduction
A Combined Gate Replacement and Input Vector Control Approach for Leakage Current Reduction
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Date
2006-02
Authors
Yuan, Lin
Qu, Gang
Advisor
Citation
L. Yuan and G. Qu. "A Combined Gate Replacement and Input Vector Control Approach for Leakage Current Reduction," IEEE Transactions on Very Large Scale Integration (VLSI) Systems, Vol. 14, No. 2, pp. 173-182, February 2006.
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Abstract
Input vector control (IVC) is a popular technique for
leakage power reduction. It utilizes the transistor stack effect in
CMOS gates by applying a minimum leakage vector (MLV) to the
primary inputs of combinational circuits during the standby mode.
However, the IVC technique becomes less effective for circuits of
large logic depth because the input vector at primary inputs has
little impact on leakage of internal gates at high logic levels. In this
paper, we propose a technique to overcome this limitation by replacing
those internal gates in their worst leakage states by other
library gates while maintaining the circuit’s correct functionality
during the active mode. This modification of the circuit does not require
changes of the design flow, but it opens the door for further
leakage reduction when the MLV is not effective. We then present
a divide-and-conquer approach that integrates gate replacement,
an optimal MLV searching algorithm for tree circuits, and a genetic
algorithm to connect the tree circuits. Our experimental results
on all the MCNC91 benchmark circuits reveal that 1) the gate
replacement technique alone can achieve 10% leakage current reduction
over the best known IVC methods with no delay penalty
and little area increase; 2) the divide-and-conquer approach outperforms
the best pure IVC method by 24% and the existing control
point insertion method by 12%; and 3) compared with the
leakage achieved by optimal MLV in small circuits, the gate replacement
heuristic and the divide-and-conquer approach can reduce
on average 13% and 17% leakage, respectively.