Quick Delay Calculation Model for Logic Circuit Optimization in Early Stages of LSI Design

Norio OHKUBO  Takeo YAMASHITA  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E86-C   No.4   pp.618-623
Publication Date: 2003/04/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on High-Performance, Low-Power System LSIs and Related Technologies)
Category: Design Methods and Implementation
Keyword: 
delay calculation,  effective capacitance,  logic circuit optimization,  delay optimization,  LSI design,  

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Summary: 
An accurate, fast delay calculation method suitable for high-performance, low-power LSI design is proposed. The delay calculation is composed of two steps: (1) the gate delay is calculated by using an effective capacitance obtained from a simple model we propose; and (2) the interconnect delay is also calculated from the effective capacitance and modified by using the gate-output transition time. The proposed delay calculation halves the error of a conventional rough calculation, achieving a computational error within 10% per gate stage. The mathematical models are simple enough that the method is suitable for quick delay calculation and logic circuit optimization in the early stages of LSI design. A delay optimization tool using this delay calculation method reduced the worst path delay of a multiply-add module by 11.2% and decreased the sizes of 58.1% of the gates.