Mixed-Signal and DSP Design Techniques [This page intentionally left blank.] [This is a blank page.] Amsterdam Boston London New York Oxford Paris San Diego San Francisco Singapore Sydney Tokyo An imprint of Elsevier Science Mixed-Signal and DSP Design Techniques by the technical staff of Analog Devices edited by Walt Kester A Volume in the Analog Devices Series Newnes is an imprint of Elsevier Science. Copyright © 2003 by Analog Devices, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Recognizing the importance of preserving what has been written, Elsevier Science prints its books on acid-free paper whenever possible. Library of Congress Cataloging-in-Publication Data ISBN: 0750676116 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. The publisher offers special discounts on bulk orders of this book. For information, please contact: Manager of Special Sales Elsevier Science 200 Wheeler Road Burlington, MA 01803 Tel: 781-313-4700 Fax: 781-313-4882 For information on all Newnes publications available, contact our World Wide Web home page at: http://www.newnespress.com 10 9 8 7 6 5 4 3 2 1 Printed in the United States of America Acknowledgments viii 1 Introduction Origins of Real-World Signals and Their Units of Measurement 3 Reasons for Processing Real-World Signals 4 Generation of Real-World Signals 5 Methods and Technologies Available for Processing Real- World Signals 6 Analog Versus Digital Signal Processing 6 A Practical Example 7 2 Sampled Data Systems Introduction 15 Discrete Time Sampling of Analog Signals 16 ADC and DAC Static Transfer Functions and DC Errors 21 AC Errors in Data Converters 28 DAC Dynamic Performance 49 3 ADCs for DSP Applications 61 Successive-Approximation ADCs 62 Sigma-Delta ADCs 69 Flash Converters 81 Subranging (Pipelined) ADCs 83 Bit-Per-Stage (Serial or Ripple) ADCs 87 4 DACs for DSP Applications 99 DAC Structures 99 Low Distortion DAC Architectures 101 DAC Logic 105 Interpolating DACs 107 Sigma-Delta DACs 109 Direct Digital Synthesis (DDS) 110 5 Fast Fourier Transforms 119 The Discrete Fourier Transform 119 The Fast Fourier Transform 127 FFT Hardware Implementation and Benchmarks 135 DSP Requirements for Real- Time FFT Applications 136 Spectral Leakage and Windowing 139 6 Digital Filters 147 Finite Impulse Response (FIR) Filters 151 FIR Filter Implementation in DSP Hardware Using Circular Buffering 156 Designing FIR Filters 159 Infinite Impulse Response (IIR) Filters 170 IIR Filter Design Techniques 173 Multirate Filters 177 Adaptive Filters 181 7 DSP Hardware 191 Microcontrollers, Microprocessors, and Digital Signal Processors ( DSPs) 191 DSP Requirements 193 ADSP-21xx 16-Bit Fixed-Point DSP Core 196 Fixed-Point Versus Floating-Point 212 ADI SHARC Floating-Point DSPs 215 ADSP-2116x Single-Instruction, Multiple-Data (SIMD) Core Architecture 220 TigerSHARC: The ADSP- TS001 Static Superscalar DSP 225 DSP Evaluation and CROSSCORE Development Tools 234 8 Interfacing to DSPs 247 Parallel Interfacing to DSP Processors: Reading Data from Memory- Mapped Peripheral ADCS 247 Parallel Interfacing to DSP Processors: Writing Data to Memory- Mapped DACS 253 Serial Interfacing to DSP Processors 258 Interfacing I/O Ports, Analog Front Ends, and Codecs to DSPs 265 High Speed Interfacing 268 DSP System Interface 269 9 DSP Applications 275 High Performance Modems for Plain Old Telephone Service (POTS) 275 Remote Access Server (RAS) Modems 281 ADSL (Asymmetric Digital Subscriber Line) 285 Digital Cellular Telephones 290 GSM Handset Using SoftFone Baseband Processor and Othello Radio 295 Analog Cellular Base Stations 301 Digital Cellular Base Stations 302 Motor Control 306 Codecs and DSPs in Voice-Band and Audio Applications 310 A Sigma-Delta ADC with Programmable Digital Filter 313 Summary 315 10 Hardware Design Techniques 321 Low Voltage Interfaces 321 Grounding in Mixed-Signal Systems 335 Digital Isolation Techniques 355 Power Supply Noise Reduction and Filtering 359 Dealing with High Speed Logic 378 Index Analog Devices Parts Index 409 viii Acknowledgments Thanks are due the many technical staff members of Analog Devices in Engineering and Marketing who provided invaluable inputs during this project. Particular credit is due the individual authors whose names appear at the beginning of their material. Special thanks go to Wes Freeman, Ed Grokulsky, Bill Chestnut, Dan King, Greg Geerling, Ken Waurin, Steve Cox, and Colin Duggan for reviewing the material for content and accuracy. Judith Douville compiled the index. Introduction Section 1 [This is a blank page.] [...]... using extensive DSP analysis of the entire signal chain, including sound source, microphone, preamp, and ADC 5 Section One Methods and Technologies Available for Processing Real-World Signals Signals may be processed using analog techniques (analog signal processing, or ASP), digital techniques (digital signal processing, or DSP) , or a combination of analog and digital techniques (mixed-signal processing,... pass band, no ripple in stop band), and the response is shown in Figure 1-5 In practice, this filter would probably be realized using three 2-pole stages, each of which requires an op amp, and several resistors and capacitors Modern filter design CAD packages make the 6-pole design relatively straightforward, but maintaining the 0.5 dB ripple specification requires accurate component selection and matching... drivers, and line receivers), dynamic range compression (log amps, LOGDACs, and programmable gain amplifiers), and filtering (both passive and active) Several methods of accomplishing signal processing are shown in Figure 1-3 The top portion of the figure shows the purely analog approach The latter parts of the figure show the DSP approach Note that once the decision has been made to use DSP techniques, ... Autocorrelation, Convolution) Capture and Store Signal in Digital Format for Analysis (FFT Techniques) Figure 1-2: Reasons for Signal Processing Generation of Real-World Signals In most of the above examples (the ones requiring DSP techniques) , both ADCs and DACs are required In some cases, however, only DACs are required where real-world analog signals may be generated directly using DSP and DACs Video raster scan... and fs/2 are not of interest and do not limit the dynamic range 18 Sampled Data Systems The antialiasing filter transition band is therefore determined by the corner frequency fa, the stop-band frequency fs – fa, and the desired stop-band attenuation, DR The required system dynamic range is chosen based on the requirement for signal fidelity fa B A fa fs – fa Kf s – f a DR fs 2 fs Kfs 2 Kfs STOP-BAND... transition region between 1 MHz and 2 MHz (1 octave) requires a minimum of 10 poles, not a trivial filter, and definitely a design challenge Therefore, other filter types are generally more suited to high speed applications where the requirement is for a sharp transition band and in-band flatness coupled with linear phase response Elliptic filters meet these criteria and are a popular choice There are... error, and two types of linearity error Offset and gain errors are analogous to offset and gain errors in amplifiers, as shown in Figure 2-10 for a bipolar input range (However, offset error and zero error, which are identical in amplifiers and unipolar data converters, are not identical in bipolar converters and should be carefully distinguished.) The transfer characteristics of both DACs and ADCs... Filtering, Modulation, Demodulation Analog Antialiasing and Reconstruction Filters with ADCs and DACs Where Common Sense and Economics Dictate Figure 1-7: Real-Time Signal Processing 10 Introduction References 1 Practical Design Techniques for Sensor Signal Conditioning, Analog Devices, 1998 2 Daniel H Sheingold, Editor, Transducer Interfacing Handbook, Analog Devices, Inc., 1972 3 Richard J Higgins,... to the analog mixing process and implies that some filtering ahead of the sampler (or ADC) is required to remove frequency components that are outside the Nyquist bandwidth, but whose aliased components fall inside it The filter performance will depend on how close the out-of-band signal is to fs/2 and the amount of attenuation required Baseband Antialiasing Filters Baseband sampling implies that the... choice of techniques is clear; in others, there is no clear-cut choice, and second-order considerations may be used to make the final decision With respect to DSP, the factor that distinguishes it from traditional computer analysis of data is its speed and efficiency in performing sophisticated digital processing functions such as filtering, FFT analysis, and data compression in real time The term mixed-signal . Science 200 Wheeler Road Burlington, MA 01803 Tel: 781-313-4700 Fax: 781-313-4882 For information on all Newnes publications available, contact our World Wide Web home page at: http://www.newnespress.com 10. ADC with Programmable Digital Filter 313 Summary 315 10 Hardware Design Techniques 321 Low Voltage Interfaces 321 Grounding in Mixed-Signal Systems 335 Digital Isolation Techniques 355 Power. 1 3 Origins of Real-World Signals and Their Units of Measurement In this book, we will primarily be dealing with the processing of real-world signals using both analog and digital techniques. Before