Opposite-Phase Clock Tree for Peak Current Reduction

Yow-Tyng NIEH  Shih-Hsu HUANG  Sheng-Yu HSU  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E90-A   No.12   pp.2727-2735
Publication Date: 2007/12/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e90-a.12.2727
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on VLSI Design and CAD Algorithms)
Category: Circuit Synthesis
Keyword: 
clocks,  design methodology,  digital circuits,  

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Summary: 
Although much research effort has been devoted to the minimization of total power consumption caused by the clock tree, no attention has been paid to the minimization of the peak current caused by it. In this paper, we propose an opposite-phase clock scheme to reduce the peak current incurred by the clock tree. Our basic idea is to balance the charging and discharging activities. According to the output operation, the clock buffers that transit simultaneously are divided into two groups: half of the clock buffers transit at the same phase of the clock source, while the other half transit at the opposite phase of the clock source. As a consequence, the opposite-phase clock scheme significantly reduces the peak current caused by the clock tree. Experimental data show that our approach can be applied at different design stages in the existing design flow.