System modeling of high-speed digital printed circuit board using SPICE


Chua, H. T. and Kung, F. W. L (1998) System modeling of high-speed digital printed circuit board using SPICE. Progress In Electromagnetics Research , PIER, 20. pp. 179-211. ISSN 1070-4698

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Implementation of digital systems is usually carried out in the form of printed circuit board (PCB) populated with active components such 180 Kung and Chuah as integrated circuits and passive components such as surface mount resistors, capacitors, sockets, connectors, cables, etc. These components together with the PCB traces and metal planes form the network which manifests as a digital PCB assembly. With the increase in operating frequency of devices in access of 100MHz and switching speed of digital devices within sub-nanoseconds, electromagnetic interference, stray parameters of components and unintentional radiation have become a major concern, affecting the integrity of a system. To cope with the issues of system performance, analog and digital circuit simulation tools are used to verify system performance in terms of signal integrity, noise margin and bandwidth under various signal patterns (vectors) and biasing during CAD layout process to ensure first-time-working prototypes. This article illustrates a structural modeling approach in which the digital PCB is considered as an assembly of parts which are modeled as electrical networks with input and output ports. The networks are linked together to form a complete system of equivalent circuit in SPICE format. Various methods have been developed by many authors [1–19] for modeling a certain aspect of the digital PCB system. Based on their work, the authors consolidate the methods and propose a structural approach to derive a system level equivalent circuit model for a digital PCB system. Section 2 outlines the modeling procedures using the structural approach. Section 3 gives the EM Field Method for deriving equivalent circuit models of sockets, connectors, interconnecting traces and discontinuities in PCB. Section 4 contains circuit models of discontinuities and IC buffers using measurement techniques. In Section 5, the power planes are modeled using a planar circuit approach [20]. A simple digital PCB system modeling example is presented in Section 6 to illustrate the proposed approach. Detailed system simulation is carried out using SPICE Version 6.1 on an IBM compatible PC. Both time and frequency domain simulations are performed. Areas of large current concentration in the power plane at any instance can be located. This allows one to determine the optimum location to install decoupling capacitors and filters to suppress EMI. An IC in the system is then replaced with a power validator. The power validator is a programmable load having the same footprint as the IC. It simulates the IC, drawing varying amount of current from the power distribution systems. An equivalent circuit is derived and SPICE simulation is performed to study the noise introduced by the die within the IC.

Item Type: Article
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: Faculty of Engineering and Technology (FET)
Depositing User: Ms Rosnani Abd Wahab
Date Deposited: 25 Nov 2013 02:33
Last Modified: 25 Nov 2013 02:33


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