Delay Modeling and Critical-Path Delay Calculation for MTCMOS Circuits

Naoaki OHKUBO  Kimiyoshi USAMI  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A   No.12   pp.3482-3490
Publication Date: 2006/12/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.12.3482
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on VLSI Design and CAD Algorithms)
Category: Simulation and Verification
Keyword: 
MTCMOS,  selective-MT,  static timing analysis,  leakage power,  delay modeling,  

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Summary: 
One of the critical issues in MTCMOS design is how to estimate a circuit delay quickly. In MTCMOS circuit, voltage on virtual ground fluctuates due to a discharge current of a logic cell. This event affects to the cell delay and makes static timing analysis (STA) difficult. In this paper, we propose a delay modeling and static STA methodology targeting at MTCMOS circuits. In the proposed method, we prepare a delay look-up table (LUT) consisting of the input slew, the output load capacitance, the virtual ground length, and a power-switch size. Using this LUT, we compute a circuit delay for each logic cell by applying the linear interpolation. This technique enables to calculate the cell delay considering the delay increase by the voltage fluctuation of virtual ground line. Experimental results show that the proposed methodology enables to estimate the cell delay and the critical path delay within 8% errors compared with SPICE simulation.