A Non-Iterative Method for Calculating the Effective Capacitance of CMOS Gates with Interconnect Load Effect

Minglu JIANG
Zhangcai HUANG
Qiang LI
Yasuaki INOUE

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E94-A    No.5    pp.1201-1209
Publication Date: 2011/05/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E94.A.1201
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: VLSI Design Technology and CAD
static timing analysis,  gate delay,  effective capacitance,  non-iterative,  

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Gate delay evaluation is always a vital concern for high-performance digital VLSI designs. As the feature size of VLSIs decreases to the nano-meter region, the work to obtain an accurate gate delay value becomes more difficult and time consuming than ever. The conventional methods usually use iterative algorithms to ensure the accuracy of the effective capacitance Ceff, which is usually used to compute the gate delay with interconnect loads and to capture the output signal shape of the real gate response. Accordingly, the efficiency is sacrificed. In this paper, an accurate and efficient approach is proposed for gate delay estimation. With the linear relationship of gate output time points and Ceff, a polynomial approximation is used to make the nonlinear effective capacitance equation be solved without iterative method. Compared to the conventional methods, the proposed method improves the efficiency of gate delay calculation. Meanwhile, experimental results show that the proposed method is in good agreement with SPICE results and the average error is 2.8%.