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Design of VLSI Systems - A Practical Introduction Linda E. M. Brackenbury Department of Computer Science Manchester University M MACMILLAN
Linda E. M. Brackenbury 1987 Softcover reprint of the hardcover 1st edition 1987 978-0-333-40821-6 All rights reserved. No reproduction, copy or transmission of this publication may be made without written permission. No paragraph of this publication may be reproduced, copied or transmitted save with written permission or in accordance with the provisions of the Copyright Act 1956 (as amended). Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. First published 1987 Published by MACMILLAN EDUCATION LTD Houndmills, Basingstoke, Hampshire RG21 2XS and London Companies and representatives throughout the world Typeset by TecSet Ltd, Wallington, Surrey British Library Cataloguing in Publication Data Brackenbury, Linda Design of VLSI systems: a practical introduction.-(macmillan computer science series) 1. Integrated circuits-very large scale integration-design and construction Data processing I. Title 621.395 TK7874 ISBN 978-0-333-40822-3 DOI 10.1007/978-1-349-18700-3 ISBN 978-1-349-18700-3 (ebook)
FOR my sons Richard and David
Contents Preface ix 1 Introduction 1 1.1 Integrated circuit trends 1 1.2 Choice of technology 1 1.3 Design approaches 3 1.4 The design process 4 1.5 Organisation and notation 6 1.6 Further reading 7 2 M OS Devices and Basic Circuits 8 2.1 The MOS structure 8 2.2 Conduction 10 2.3 Threshold voltage 11 2.4 Ids versus V ds characteristic for NMOS devices 13 2.5 Characteristic equation for PMOS devices 17 2.6 Principles of inverters 18 2.7 NMOS inverter with a resistor load 20 2.8 NMOS inverter with an NMOS enhancement transistor load 21 2.9 NMOS inverter with an NMOS depletion transistor load 23 2.10 Edge times for NMOS inverter with a depletion load 25 2.11 Ratioed and ratioless design 29 2.12 The CMOS inverter 30 2.13 NMOS pass transistors 36 2.14 Ratioless NMOS inverter 38 2.15 CMOS pass gate 39 2.16 Buffer circuits 40 2.17 Further reading 44 3 Fabrication and Design Rules 45 3.1 The MOS process 45 3.2 NMOS processing 47 3.3 The CMOS process 50 3.4 Yield 52 3.5 Electrical parameters 53
viii Contents 3.6 Scaling 56 3.7 Design rules 58 3.8 Stick diagrams 62 3.9 Further reading 63 4 MOS Logical Circuit Design 64 4.1 Combinational and sequential logic 64 4.2 Random logic 65 4.3 Pass transistor array 70 4.4 Programmable logic array 72 4.5 Static flip flops 78 4.6 Dynamic flip flops 86 4.7 Random access memory 94 4.8 Further reading 103 s System Considerations 104 5.1 System to logic translation 104 5.2 Full custom and semi-custom design l06 5.3 Control 108 5.4 Timing 114 5.5 Testability 118 5.6 Further reading 124 6 A Design Example 127 6.1 System specification 127 6.2 Architecture 129 6.3 Logic design 132 6.4 Circuit design 136 6.5 Layout, placement and interconnections 141 6.6 Fabrication and testing 147 Index 151
Preface The wider availability of fabrication facilities has led to an increasing number of computer scientists and engineers wishing to learn about and participate in the design of silicon chips. This book aims to provide an introduction to all the stages involved in committing a design on to silicon, ranging from system considerations and logic circuits to the design of these circuits on each layer of silicon and their fabrication. The material is largely based on lectures given to second and third year undergraduates in the Department of Computer Science at Manchester University and aims to provide not only an understanding of the principles of the design procedure but also to maintain a practical approach. It is intended that the text should equip the firsttime chip designer with the confidence and competence to attempt to produce a working integrated circuit. Consistent with these aims, the text concentrates on safe design techniques. Also, in the interests of clarity and an improved appreciation of the principles involved, design features are usually discussed with reference to a particular example. The use of rigorous mathematics is avoided, since the accurate analysis of circuits is long and complex and often tends to obscure tlie essential principles. Only an elementary knowledge of electrical fundamentals is assumed. The text should therefore be suitable for undergraduate and postgraduate students in electronic and computer engineering and allied disciplines. It is also hoped that the material will prove to be useful to those actively involved in chip design. I have gained much experience from undertaking a chip design. In this respect, I should like to thank Professor D. B. G. Edwards in the Computer Science Department at Manchester University for his interest and encouragement. I am also grateful to the Science and Engineering Research Council for the use of their facilities. Finally, a word of appreciation to my husband, Allan, for his help in the preparation of this text.