Sigma-Delta Converters: Practical Design Guide
Description
Sigma-Delta Modulators (SDMs) have become one of the best choices for the implementation of analog/digital interfaces of electronic systems integrated in CMOS technologies. Compared to other kinds of Analog-to-Digital Converters (ADCs), SigmadeltaMs cover one of the widest conversion regions of the resolution-versus-bandwidth plane, being the most efficient solution to digitize signals in an increasingly number of applications, which span from high-resolution low-bandwidth digital audio, sensor interfaces, and instrumentation, to ultra-low power biomedical systems and medium-resolution broadband wireless communications.
Following the spirit of its first edition, Sigma-Delta Converters: Practical Design Guide, 2nd Edition takes a comprehensive look at SDMs, their diverse types of architectures, circuit techniques, analysis synthesis methods, and CAD tools, as well as their practical design considerations. It compiles and updates the current research reported on the topic, and explains the multiple trade-offs involved in the whole design flow of Sigma-Delta Modulators--from specifications to chip implementation and characterization. The book follows a top-down approach in order to provide readers with the necessary understanding about recent advances, trends, and challenges in state-of-the-art SigmadeltaMs. It makes more emphasis on two key points, which were not treated so deeply in the first edition:
* It includes a more detailed explanation of SigmadeltaMs implemented using Continuous-Time (CT) circuits, going from system-level synthesis to practical circuit limitations.
* It provides more practical case studies and applications, as well as a deeper description of the synthesis methodologies and CAD tools employed in the design of Sigmadelta converters.
Sigma-Delta Converters: Practical Design Guide, 2nd Edition serves as an excellent textbook for undergraduate and graduate students in electrical engineering as well as design engineers working on SD data-converters, who are looking for a uniform and self-contained reference in this hot topic. With this goal in mind, and based on the feedback received from readers, the contents have been revised and structured to make this new edition a unique monograph written in a didactical, pedagogical, and intuitive style.
More details
Other editions
Additional editions
Person
José M. de la Rosa is a Professor at the Institute of Microelectronics of Seville, IMSE-CNM (CSIC, University of Seville, Spain). His main research interests are in the field of analog and mixed-signal integrated circuits, especially high-performance sigma-delta converters. He has worked in a number of international research and industrial projects and has co-authored over 200 peer-reviewed conference and journal papers dealing with sigma-delta ADCs. He served as Associated Editor of the IEEE Transactions on Circuits and Systems I: Regular Papers, as Deputy Editor in Chief of the IEEE Transactions on Circuits and Systems II: Express Briefs, and as Distinguished Lecturer of the IEEE Circuits and Systems Society.
Content
Preface xix
Acknowledgements xxv
List of Abbreviations xxvii
1 Introduction to ¿¿¿¿¿¿¿¿ Modulators: Fundamentals, Basic Architecture and Performance Metrics 1
1.1 Basics of Analog-to-Digital Conversion 2
1.1.1 Sampling 3
1.1.2 Quantization 4
1.1.3 Quantization White Noise Model 5
1.1.4 Noise Shaping 8
1.2 Sigma-Delta Modulation 9
1.2.1 From Noise-shaped Systems to S¿ Modulators 10
1.2.2 Performance Metrics of S¿Ms 11
1.3 The First-order S¿ Modulator 13
1.4 Performance Enhancement and Taxonomy of S¿Ms 16
1.4.1 S¿M System-level Design Parameters and Strategies 17
1.4.2 Classification of S¿Ms 18
1.5 Putting All The Pieces Together: From S¿Ms to S¿ ADCs 19
1.5.1 Some Words about S¿ Decimators 20
1.6 S¿ DACs 22
1.6.1 System Design Trade-offs and Signal Processing in S¿ DACs 22
1.6.2 Implementation of Digital S¿Ms used in DACs 24
1.7 Summary 25
References 26
2 Taxonomy of ¿¿¿¿¿¿¿¿ Architectures 29
2.1 Second-order S¿ Modulators 30
2.1.1 Alternative Representations of Second-order S¿Ms 31
2.1.2 Second-Order S¿M with Unity STF 34
2.2 High-order Single-loop S¿Ms 35
2.3 Cascade S¿ Modulators 39
2.3.1 SMASH S¿M Architectures 46
2.4 Multi-bit S¿ Modulators 49
2.4.1 Influence of Multi-bit DAC Errors 49
2.4.2 Dynamic Element Matching Techniques 50
2.4.3 Dual Quantization 53
2.4.3.1 Dual-quantization Single-loop S¿Ms 53
2.4.3.2 Dual-quantization Cascade S¿Ms 54
2.5 Band-pass S¿ Modulators 55
2.5.1 Quadrature BP-S¿Ms 56
2.5.2 The z ¿ -z2 LP-BP Transformation 58
2.5.3 BP-S¿Ms with Optimized NTF 58
2.5.4 Time-interleaved and Polyphase BP-S¿Ms 61
2.6 Continuous-time S¿ Modulators: Architecture and Basic Concepts 64
2.6.1 An Intuitive Analysis of CT-S¿Ms 66
2.6.2 Some Words about Alias Rejection in CT-S¿Ms 69
2.7 DT-CT Transformation of S¿Ms 70
2.7.1 The Impulse-invariant Transformation 70
2.7.2 DT-CT Transformation of a Second-order S¿M 72
2.8 Direct Synthesis of CT-S¿Ms 74
2.9 Summary 76
References 76
3 Circuit Errors in Switched-capacitor ¿¿¿¿¿¿¿¿ Modulators 83
3.1 Overview of Nonidealities in Switched-capacitor S¿ Modulators 84
3.2 Finite Amplifier Gain in SC-S¿Ms 86
3.3 Capacitor Mismatch in SC-S¿Ms 90
3.4 Integrator Settling Error in SC-S¿Ms 91
3.4.1 Behavioral Model for the Integrator Settling 91
3.4.2 Linear Effect of Finite Amplifier Gain-Bandwidth Product 95
3.4.3 Nonlinear Effect of Finite Amplifier Slew Rate 98
3.4.4 Effect of Finite Switch On-resistance 100
3.5 Circuit Noise in SC-S¿Ms 101
3.6 Clock Jitter in SC-S¿Ms 105
3.7 Sources of Distortion in SC-S¿Ms 107
3.7.1 Nonlinear Amplifier Gain 107
3.7.2 Nonlinear Switch On-Resistance 109
3.8 Case Study: High-level Sizing of a S¿M 111
3.8.1 Ideal Modulator Performance 111
3.8.2 Noise Leakages 112
3.8.3 Circuit Noise 115
3.8.4 Settling Error 116
3.8.5 Overall High-Level Sizing and Noise Budget 117
3.9 Summary 119
References 119
4 Circuit Errors and Compensation Techniques in Continuous-time ¿¿¿¿¿¿¿¿ Modulators 123
4.1 Overview of Nonidealities in Continuous-time S¿ Modulators 123
4.2 CT Integrators and Resonators 124
4.3 Finite Amplifier Gain in CT-S¿Ms 126
4.4 Time-constant Error in CT-S¿Ms 128
4.5 Finite Integrator Dynamics in CT-S¿Ms 130
4.5.1 Effect of Finite Gain-Bandwidth Product on CT-S¿Ms 131
4.5.2 Effect of Finite Slew Rate on CT-S¿Ms 133
4.6 Sources of Distortion in CT-S¿Ms 134
4.6.1 Nonlinearities in the Front-end Integrator 134
4.6.2 Intersymbol Interference in the Feedback DAC 136
4.7 Circuit Noise in CT-S¿Ms 137
4.7.1 Noise Analysis Considering NRZ Feedback DACs 137
4.7.2 Noise Analysis Considering SC Feedback DACs 139
4.8 Clock Jitter in CT-S¿Ms 140
4.8.1 Jitter in Return-to-zero DACs 141
4.8.2 Jitter in Non-return-to-zero DACs 142
4.8.3 Jitter in Switched-capacitor DACs 144
4.8.4 Lingering Effect of Clock Jitter Error 145
4.8.5 Reducing the Effect of Clock Jitter with FIR and Sine-shaped DACs 147
4.9 Excess Loop Delay in CT-S¿Ms 149
4.9.1 Intuitive Analysis of ELD 149
4.9.2 Analysis of ELD based on Impulse-invariant DT-CT Transformation 151
4.9.3 Alternative ELD Compensation Techniques 154
4.10 Quantizer Metastability in CT-S¿Ms 155
4.11 Summary 159
References 160
5 Behavioral Modeling and High-level Simulation 165
5.1 Systematic Design Methodology of S¿ Modulators 165
5.1.1 System Partitioning and Abstraction Levels 167
5.1.2 Sizing Process 167
5.2 Simulation Approaches for the High-level Evaluation of S¿Ms 169
5.2.1 Alternatives to Transistor-level Simulation 169
5.2.2 Event-driven Behavioral Simulation Technique 171
5.2.3 Programming Languages and Behavioral Modeling Platforms 172
5.3 Implementing S¿M Behavioral Models 173
5.3.1 From Circuit Analysis to Computational Algorithms 173
5.3.2 Time-domain versus Frequency-domain Behavioral Models 175
5.3.3 Implementing Time-domain Behavioral Models in MATLAB 178
5.3.4 Building Time-domain Behavioral Models as SIMULINK C-MEX S-functions 182
5.4 Efficient Behavioral Modeling of S¿M Building Blocks using C-MEX S-functions 188
5.4.1 Modeling of SC Integrators using S-functions 188
5.4.1.1 Capacitor Mismatch and Nonlinearity 190
5.4.1.2 Input-referred Thermal Noise 191
5.4.1.3 Switch On-resistance Dynamics 194
5.4.1.4 Incomplete Settling Error 197
5.4.2 Modeling of CT Integrators using S-functions 200
5.4.2.1 Single-pole Gm-C Model 200
5.4.2.2 Two-pole Dynamics Model 201
5.4.2.3 Modeling Transconductors as S-functions 203
5.4.3 Behavioral Modeling of Quantizers using S-functions 205
5.4.3.1 Modeling Multi-level ADCs as S-functions 205
5.4.3.2 Modeling Multi-level DACs as S-functions 207
5.5 SIMSIDES: A SIMULINK-based Behavioral Simulator for S¿Ms 209
5.5.1 Model Libraries Included in SIMSIDES 210
5.5.2 Structure of SIMSIDES and its User Interface 211
5.5.2.1 Creating a New S¿M Block Diagram 212
5.5.2.2 Setting Model Parameters 215
5.5.2.3 Simulation Analyses 215
5.6 Using SIMSIDES for High-level Sizing and Verification of S¿Ms 216
5.6.1 SC Second-order Single-Bit S¿M 216
5.6.1.1 Effect of Amplifier Finite DC Gain 218
5.6.1.2 Effect of Thermal Noise 218
5.6.1.3 Effect of the Incomplete Settling Error 220
5.6.1.4 Cumulative Effect of All Errors 221
5.6.2 CT Fifth-order Cascade 3-2 Multi-bit S¿M 224
5.6.2.1 Effect of Nonideal Effects 227
5.6.2.2 High-level Synthesis and Verification 229
5.7 Summary 231
References 231
6 Automated Design and Optimization of ¿¿¿¿¿¿¿¿Ms 235
6.1 Architecture Exploration and Selection: Schreier's Toolbox 236
6.1.1 Basic Functions of Schreier's Delta-Sigma Toolbox 236
6.1.2 Synthesis of a Fourth-order CRFF LP/BP SC-S¿M with Tunable Notch 238
6.1.3 Synthesis of a Fourth-order BP CT-S¿M with Tunable Notch 240
6.2 Optimization-based High-level Synthesis of S¿ Modulators 245
6.2.1 Combining Behavioral Simulation and Optimization 246
6.2.2 Using Simulated Annealing as Optimization Engine 247
6.2.3 Combining SIMSIDES with MATLAB Optimizers 253
6.3 Lifting Method and Hardware Acceleration to Optimize CT-S¿Ms 255
6.3.1 Hardware Emulation of CT-S¿Ms on an FPGA 257
6.3.2 GPU-accelerated Computing of CT-S¿Ms 258
6.4 Using Multi-objective Evolutionary Algorithms to Optimize S¿Ms 259
6.4.1 Combining MOEA with SIMSIDES 261
6.4.2 Applying MOEA and SIMSIDES to the Synthesis of CT-S¿Ms 262
6.5 Summary 269
References 269
7 Electrical Design of ¿¿¿¿¿¿¿¿Ms: From Systems to Circuits 271
7.1 Macromodeling S¿Ms 272
7.1.1 SC Integrator Macromodel 272
7.1.1.1 Switch Macromodel 272
7.1.1.2 OTA Macromodel 274
7.1.2 CT Integrator Macromodel 274
7.1.2.1 Active-RC Integrators 274
7.1.2.2 Gm-C Integrators 274
7.1.3 Nonlinear OTA Transconductor 275
7.1.4 Embedded Flash ADC Macromodel 276
7.1.5 Feedback DAC Macromodel 277
7.2 Examples of S¿M Macromodels 279
7.2.1 SC Second-order Example 279
7.2.2 Second-order Active-RC S¿M 283
7.3 Including Noise in Transient Electrical Simulations of S¿Ms 286
7.3.1 Generating and Injecting Noise Data Sequences in HSPICE 287
7.3.2 Analyzing the Impact of the Main Noise Sources in SC Integrators 289
7.3.3 Generating and Injecting Flicker Noise Sources in Electrical Simulations 289
7.3.4 Test Bench to Include Noise in the Simulation of S¿Ms 293
7.4 Processing S¿M Output Results of Electrical Simulations 294
7.5 Summary 298
References 298
8 Design Considerations of ¿¿¿¿¿¿¿¿M Subcircuits 301
8.1 Design Considerations of CMOS Switches 302
8.1.1 Trade-Off Between Ron and the CMOS Switch Drain/Source Parasitic Capacitances 302
8.1.2 Characterizing the Nonlinear Behavior of Ron 302
8.1.3 Influence of Technology Downscaling on the Design of Switches 304
8.1.4 Evaluating Harmonic Distortion due to CMOS Switches 305
8.2 Design Considerations of Operational Amplifiers 308
8.2.1 Typical Amplifier Topologies 309
8.2.2 Common-mode Feedback Networks 311
8.2.3 Characterization of the Amplifier in AC 313
8.2.4 Characterization of the Amplifier in DC 313
8.2.5 Characterization of the Amplifier Gain Nonlinearity 316
8.3 Design Considerations of Transconductors 317
8.3.1 Highly Linear Front-end Transconductor 318
8.3.2 Loop-filter Transconductors 320
8.3.3 Widely Programmable Transconductors 323
8.4 Design Considerations of Comparators 324
8.4.1 Regenerative Latch-based Comparators 325
8.4.2 Design Guidelines of Comparators 327
8.4.3 Characterization of Offset and Hysteresis Based on the Input-ramp Method 328
8.4.4 Characterization of Offset and Hysteresis Based on the Bisectional Method 328
8.4.5 Characterizing the Comparison Time 330
8.5 Design Considerations of Current-Steering DACs 332
8.5.1 Fundamentals and Basic Concepts of CS DACs 333
8.5.2 Practical Realization of CS DACs 333
8.5.3 Current Cell Circuits, Error Limitations, and Design Criteria 336
8.5.4 CS 4-bit DAC Example 336
8.6 Summary 338
References 338
9 Practical Realization of ¿¿¿¿¿¿¿¿Ms: From Circuits to Chips 341
9.1 Auxiliary S¿M Building Blocks 341
9.1.1 Clock-phase Generators 342
9.1.1.1 Phase Generation 342
9.1.1.2 Phase Buffering 342
9.1.1.3 Phase Distribution 344
9.1.2 Generation of Common-mode Voltage, Reference Voltage, and Bias Currents 345
9.1.2.1 Bandgap Circuit 345
9.1.2.2 Reference Voltage Generator 345
9.1.2.3 Master Bias Current Generator 346
9.1.2.4 Common-mode Voltage Generator 346
9.1.3 Additional Digital Logic 347
9.2 Layout Design, Floorplanning, and Practical Issues 348
9.2.1 Layout Floorplanning 348
9.2.1.1 Divide Layout into Different Parts or Regions 348
9.2.1.2 Shield Sensitive S¿M Analog Subcircuits from Switching Noise 349
9.2.1.3 Buses to Distribute Signals Shared by Different S¿M Parts 349
9.2.1.4 Be Obsessive about Layout Symmetry and Details of Analog Parts 349
9.2.2 I/O Pad Ring 350
9.2.3 Importance of Layout Verification and Catastrophic Failure 350
9.3 Chip Package, Test PCB, and Experimental Setup 354
9.3.1 Bonding Diagram and Package 354
9.3.2 Test PCB 355
9.4 Experimental Test Set-Up 355
9.4.1 Planning the Type and Number of Instruments Needed 357
9.4.2 Connecting Lab Instruments 357
9.4.3 Measurement Set-Up Example 358
9.5 S¿M Design Examples and Case Studies 359
9.5.1 Programmable-gain S¿Ms for High Dynamic Range Sensor Interfaces 360
9.5.1.1 Main Design Criteria and Performance Limitations 361
9.5.1.2 SC Realization with Programmable Gain and Double Sampling 362
9.5.1.3 Influence of Chopper Frequency on Flicker Noise 362
9.5.2 Reconfigurable SC-S¿Ms for Multi-standard Direct Conversion Receivers 364
9.5.2.1 Power-scaling Circuit Techniques 367
9.5.2.2 Experimental Results 368
9.5.3 Using Widely-programmable Gm-LC BP-S¿Ms for RF Digitizers 368
9.5.3.1 Application Scenario 371
9.5.3.2 Gm-LC BP-S¿M High-level Sizing 371
9.5.3.3 BP CT-S¿M Loop-Filter Reconfiguration Techniques 375
9.5.3.4 Embedded 4-bit Quantizer with Calibration 378
9.5.3.5 Biasing, Digital Control Programmability and Testability 382
9.6 Summary 385
References 386
10 Frontiers, Trends and Challenges: Towards Next-generation ¿¿¿¿¿¿¿¿ Modulators 389
10.1 State-of-the-Art ADCs: Nyquist-rate versus S¿ Converters 390
10.1.1 Conversion Energy 391
10.1.2 Figures of Merit 392
10.2 Comparison of Different Categories of S¿ ADCs 393
10.2.1 Aperture Plot of S¿Ms 406
10.2.2 Energy Plot of S¿Ms 407
10.3 Empirical and Statistical Analysis of State-of-the-Art S¿Ms 408
10.3.1 SC versus CT S¿Ms 408
10.3.2 Technology used in State-of-the-Art S¿Ms 410
10.3.3 Single-Loop versus Cascade S¿Ms 410
10.3.4 Single-bit versus Multi-bit S¿Ms 411
10.3.5 Low-pass versus Band-pass S¿Ms 413
10.3.6 Emerging S¿M Techniques 415
10.4 Gigahertz-range S¿Ms for RF-to-digital Conversion 415
10.5 Enhanced Cascade S¿Ms 418
10.5.1 SMASH CT-S¿Ms 418
10.5.2 Two-stage 0-L MASH 419
10.5.3 Stage-sharing Cascade S¿Ms 420
10.5.4 Multi-rate and Hybrid CT/DT S¿Ms 420
10.5.4.1 Upsampling Cascade MR-S¿Ms 421
10.5.4.2 Downsampling Hybrid CT/DT Cascade MR-S¿Ms 422
10.6 Power-efficient S¿M Loop-filter Techniques 423
10.6.1 Inverter-based S¿Ms 423
10.6.2 Hybrid Active/Passive and Amplifier-less S¿Ms 424
10.6.3 Power-efficient Amplifier Techniques 426
10.7 Hybrid S¿M/Nyquist-rate ADCs 428
10.7.1 Multi-bit S¿M Quantizers based on Nyquist-rate ADCs 428
10.7.2 Incremental S¿ ADCs 429
10.8 Time-based S¿ ADCs 431
10.8.1 S¿Ms with VCO/PWM-based Quantization 432
10.8.2 Scaling-friendly Mostly-digital S¿Ms 433
10.8.3 GRO-based S¿Ms 434
10.9 DAC Techniques for High-performance CT-S¿Ms 436
10.10 Classification of State-of-the-Art References 437
10.11 Summary and Conclusions 437
References 438
A State-space Analysis of Clock Jitter in CT-¿¿¿¿¿¿¿¿Ms 463
A.1 State-space Representation of NTF (z) 463
A.2 Expectation Value of (¿qn)2 465
A.3 In-band Noise Power due to Clock Jitter 466
References 467
B SIMSIDES User Guide 469
B.1 Getting Started: Installing and Running SIMSIDES 470
B.2 Building and Editing S¿M Architectures in SIMSIDES 470
B.3 Analyzing S¿Ms in SIMSIDES 473
B.3.1 Node Spectrum Analysis 474
B.3.2 Integrated Power Noise 474
B.3.3 SNR/SNDR 475
B.3.4 Harmonic Distortion 475
B.3.5 Integral and Differential Non-Linearity 477
B.3.6 Multi-tone Power Ratio 477
B.3.7 Histogram 478
B.3.8 Parametric Analysis 478
B.3.9 Monte Carlo Analysis 479
B.4 Optimization Interface 480
B.5 Tutorial Example: Using SIMSIDES to Model and Analyze S¿Ms 482
B.5.1 Creating the Cascade 2-1 S¿M Block Diagram in SIMSIDES 482
B.5.2 Setting Model Parameters 482
B.5.3 Computing the Output Spectrum 484
B.5.4 SNR versus Input Amplitude Level 486
B.5.5 Parametric Analysis Considering Only One Parameter 487
B.5.6 Parametric Analysis Considering Two Parameters 488
B.5.7 Computing Histograms 489
B.6 Getting Help 489
C SIMSIDES Block Libraries and Models 491
C.1 Overview of SIMSIDES Libraries 491
C.2 Ideal Libraries 492
C.2.1 Ideal Integrators 492
C.2.1.1 Building-block Model Purpose and Description 492
C.2.1.2 Model Parameters 493
C.2.2 Ideal Resonators 493
C.2.2.1 Ideal_LD_Resonator 493
C.2.2.2 Ideal_FE_Resonator 493
C.2.2.3 Ideal_CT_Resonator 493
C.2.3 Ideal Quantizers 494
C.2.3.1 Ideal_Comparator 494
C.2.3.2 Ideal_Comparator_for_SI 495
C.2.3.3 Ideal_Multibit_Quantizer 495
C.2.3.4 Ideal_Multibit_Quantizer_for_SI 496
C.2.3.5 Ideal_Multibit_Quantizer_levels 496
C.2.3.6 Ideal_Multibit_Quantizer_levels_SD2 496
C.2.3.7 Ideal_Sampler 496
C.2.4 Ideal D/A Converters 496
C.2.4.1 Ideal_DAC_for_SI 496
C.2.4.2 Ideal_DAC_dig_level_SD2 497
C.3 Real SC Building-Block Libraries 497
C.3.1 Real SC Integrators 497
C.3.2 Real SC Resonators 501
C.4 Real SI Building-Block Libraries 503
C.4.1 Real SI Integrators 503
C.4.2 Real SI Resonators 505
C.4.3 SI Errors and Model Parameters 506
C.4.3.1 Basic_SI_FE(LD)_Integrator and Basic_SI_FE(LD)_Resonator 506
C.4.3.2 SI_FE(LD)_Int_Finite_Conductance 507
C.4.3.3 SI_FE(LD)_Int_Finite_Conductance & Settling & ChargeInjection 508
C.5 Real CT Building-Block Libraries 508
C.5.1 Real CT Integrators 508
C.5.1.1 Model Parameters used in Transconductors and Gm-C Integrator Building Blocks 511
C.5.1.2 Gm-MC Integrators 511
C.5.1.3 Active-RC Integrators 512
C.5.1.4 MOSFET-C Integrators 513
C.5.2 Real CT Resonators 513
C.5.2.1 Gm-C Resonators 514
C.5.2.2 Gm-LC Resonators 517
C.6 Real Quantizers & Comparators 517
C.7 Real D/A Converters 518
C.8 Auxiliary Blocks 519
Index 523
Preface
Sigma-Delta modulators ( Ms) have become one of the best choices for the implementation of analog/digital interfaces of electronic systems integrated in CMOS technologies. Compared to other kinds of analog-to-digital converters (ADCs), Ms cover the widest conversion region of the resolution-versus-bandwidth plane. They are the most efficient way to digitize very diverse types of signal in an increasing number of application scenarios, from high-resolution low-bandwidth data conversions for digital audio, sensor interfaces, and instrumentation, to ultra-low-power biomedical systems and medium-resolution broadband wireless communications. This versatility, together with their robustness and their simplicity in many practical situations, has made more and more engineers today consider Ms as the first choice for their research projects and their industrial products.
The idea underlying the operation of Ms was patented by Cutler in 1960 [1], although its application to the construction of data converters was first reported in the published literature by Inose et al. in 1962 [2]. The operation of Ms is relatively simple to describe, although sometimes very difficult to analyze. Essentially, the fundamental principle behind Ms is based on the combination of two signal processing techniques, namely: oversampling and quantization noise shaping. The former consists of taking the signal samples at a higher rate than the one dictated by the Nyquist sampling theorem. These samples are commonly quantized with a large error using a low-resolution quantizer. The resulting oversampled quantization error is filtered in the modulator feedback loop, so that its frequency spectrum is shaped in such a way that a large portion of its power is pushed out of the signal band, where it is removed by a digital filter. The outcome of the combined action of oversampling and noise shaping allows Ms to achieve high-precision digitization using a low-resolution coarse quantizer. Therefore, unlike other kinds of ADC architectures that require high-precision analog circuits, Ms trade the accuracy of their analog circuitry for speed of digital signal processing, thus achieving a higher degree of insensitivity to circuit error mechanisms and potentially benefiting from CMOS technology's evolution towards the nanometer scale.
Prompted by these benefits and fueled by technology downscaling and industry trends in consumer digital electronics, the original concept of noise shaping described above has evolved over the last five decades through many M generations, giving rise to a plethora of architectures, circuit- and system-design techniques, and a number of integrated circuits (ICs), which have pushed the state of the art on Ms forward, yielding innovative research results and successful industry products.
All these advances and research studies have led (and continue to do so) to a vast amount of technical literature. Indeed, since the publication of pioneering works such as the widely cited papers written by Candy [(3, 4] and Boser and Wooley [5], the number of publications has increased significantly, now including hundreds of patents, thousands of research papers, some tutorial papers [(6-8], as well as dozens of introductory and specialized monographs [(9-31]. However, with so much material and such an abundance of technical information published, many designers - particularly novel designers, but also some experienced designers focused on specific subtopics of Ms - may become sometimes disoriented and lose their way. This has motivated some authors to put all these pieces of information together in a comprehensive and systematic way.
Apart from earlier books aiming to catalogue the existing publications on Ms [ (9) ], one of the first attempts to present a guide for M designers is the book edited by Norsworthy et al. in 1997 [10], also known as "the yellow book" by the M community. This book, which deals with a number of important subjects in Ms, had contributions by a number of experts in the field, thus making it hard to present its contents in a coherent and consistent way. With this objective in mind, some authors have put their efforts into writing tutorial monographs dealing with the systematic design of Ms.
Among others, the book written by Schreier and Temes, published in 2005 [21], often referred to as "the green book", has become one of the most popular books on converters. This book provides an excellent and comprehensive treatment of Ms, their operating principles, and main architectures, presenting several design examples constructed using the well-known Schreier's MATLAB toolbox [32]. A revised second edition of this book was written by Pavan, Schreier and Temes, and was published in 2017 [33]. This new edition expanded the contents of the first edition with more sections dealing with continuous-time (CT) circuit implementations and circuit design considerations, without losing the main intention of the first edition, namely to give a basic understanding of the operation of converters.
Some other remarkable and pioneering examples are the book written by Medeiro et al. in 1999 [13] - focused on the systematic design of SC Ms - and the book of Ortmanns and Gerfers [22], published in 2006, which is still one of the most complete monographs on CT Ms to date. All of these books, as well as other monographs reported in the technical literature, give incomplete views of Ms, paying more attention to particular aspects of their design, and/or a type of architecture, circuit technique, or application.
This being the case, and following the spirit of the first edition of this book, this second edition attempts to cover some of these knowledge gaps in the literature, by providing a comprehensive and systematic description of the universe of Ms, their diverse architectures, circuit techniques, analysis and synthesis methods and CAD tools, as well as their practical design considerations. As in the first edition, one of the main purposes of this book is to be an educational and reference textbook for undergraduate and graduate students. With this goal in mind, and based on the courses already given by the author and the feedback received from readers and course attendees, the contents of the second edition of the book have been updated, completed and structured to address a large audience: from senior designers who want to acquire a deeper and up-to-date insight into Ms, to inexperienced engineers who are looking for a uniform and self-contained reference into this hot topic. The new contents and materials make this new edition a unique monograph, a result of the compiling and updating of the enormous number of technical and research studies reported to date on the topic of Ms. It presents the results of this compilation in a didactical, pedagogical, and intuitive style.
Another key feature of this book (as mentioned in the title) is that it can be used as a practical guide for designers, emphasizing explanations of the multiple trade-offs involved in the whole design flow of Ms - from specifications to chip implementation and characterization. To this end, a top-down approach is followed, presenting the contents in a hierarchical way; in other words, going from the theoretical fundamentals, system-level design equations, and behavioral models to circuit, transistor-level, and physical implementations, in order to provide readers with the necessary understanding and insights into the recent advances, trends, and challenges involved in the design of state-of-the-art M ICs.
This second edition emphasizes two key points, which were not covered in such depth in the first edition. The first is to include more detailed explanation of Ms implemented using CT circuits, going from system-level synthesis to practical circuit/physical limitations. The second point is to include more practical case studies and applications, as well giving a deeper description of the synthesis methodologies and CAD tools employed in the design of converters. Due to the quantity of all these new materials, the table of contents of the first edition has been re-organized and expanded, going from five chapters and two appendixes to ten chapters and three appendixes in this second edition.
The top-down approach adopted in this book inspires the hierarchical way in which the contents are structured. Thus, Chapter 1 begins from the top, giving an introduction to data converters and explaining the basic concepts and fundamentals behind modulation, its main building blocks, the signal processing involved, its performance metrics and basic examples to illustrate the concepts of noise shaping and oversampling - the main ingredients of converters. Chapter 2 gives a taxonomical description of the diverse variety of M architectures, the nature of signals (low-pass and band-pass), as well as the dynamics involved (either discrete-time or continuous-time). In this chapter, Ms are considered ideal systems, except for their inherent quantization error; CT synthesis methods and architectures will be explained in more detail than in the first edition of the book.
Chapters 3 and 4 descend one level in the modulator hierarchy to...
