Variant X-Tree Clock Distribution Network and Its Performance Evaluations

Xu ZHANG  Xiaohong JIANG  Susumu HORIGUCHI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.10   pp.1909-1918
Publication Date: 2007/10/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.10.1909
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on VLSI Technology toward Frontiers of New Market)
Category: Low-Power and High-Performance VLSI Circuit Technology
Keyword: 
clock distribution network (CDN),  Variant X-Tree,  X Architecture,  H-Tree,  clock skew,  

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Summary: 
The evolution of VLSI chips towards larger die size, smaller feature size and faster clock speed makes the clock distribution an increasingly important issue. In this paper, we propose a new clock distribution network (CDN), namely Variant X-Tree, based on the idea of X-Architecture proposed recently for efficient wiring within VLSI chips. The Variant X-Tree CDN keeps the nice properties of equal-clock-path and symmetric structure of the typical H-Tree CDN, but results in both a lower maximal clock delay and a lower clock skew than its H-Tree counterpart, as verified by an extensive simulation study that incorporates simultaneously the effects of process variations and on-chip inductance. We also propose a closed-form statistical models for evaluating the skew and delay of the Variant X-Tree CDN. The comparison between the theoretical results and the simulation results indicates that the proposed statistical models can be used to efficiently and rapidly evaluate the performance of the variant X-Tree CDNs.