The Data Conversion Handbook

Chapter 1: Data Converter History ........................................................................................3 Section 1-1: Early History .............................................................................................................5 The Early Years: Telegraph to Telephone .......................................................................................... 6 The Invention of PCM ....................................................................................................................... 8 The Mathematical Foundations of PCM ........................................................................................... 9 The PCM Patents of Alec Harley Reeves ........................................................................................ 10 PCM and the Bell System: World War II through 1948 .................................................................. 11 Op Amps and Regenerative Repeaters: Vacuum Tubes to Solid-State ............................................ 13 Section 1-2: Data Converters of the 1950s and 1960s ...................................................................19 Commercial Data Converters: 1950s ............................................................................................... 19 Commercial Data Converter History: 1960s ................................................................................... 20 Data Converter Architectures .......................................................................................................... 23 Section 1-3: Data Converters of the 1970s ...................................................................................27 Monolithic Data Converters of the 1970s ........................................................................................28 Bipolar Process IC DACs of the 1970s ...........................................................................................28 CMOS IC DACs of the 1970s ......................................................................................................... 29 Monolithic ADCs of the 1970s ........................................................................................................ 31 Hybrid Data Converters of the 1970s .............................................................................................. 32 Modular Data Converters of the 1970s ............................................................................................ 35 Section 1-4: Data Converters of the 1980s ...................................................................................39 Monolithic DACs of the 1980s ........................................................................................................ 40 Monolithic ADCs of the 1980s ........................................................................................................ 41 Monolithic Flash ADCs of the 1980s .............................................................................................. 42 Hybrid and Modular DACs and ADCs of the 1980s ....................................................................... 42 Section 1-5: Data Converters of the 1990s ...................................................................................45 Monolithic DACs of the 1990s ........................................................................................................ 46 Monolithic ADCs of the 1990s ........................................................................................................ 48 Hybrid and Modular DACs and ADCs of the 1990s ....................................................................... 52 Section 1-6: Data Converters of the 2000s ...................................................................................53 Chapter 2: Fundamentals of Sampled Data Systems ...............................................................57 Section 2-1: Coding and Quantizing .............................................................................................57 Unipolar Codes ................................................................................................................................ 59 Gray Code ........................................................................................................................................ 61 Bipolar Codes .................................................................................................................................. 62 TLFeBOOKvi Contents Complementary Codes .................................................................................................................... 65 DAC and ADC Static Transfer Functions and DC Errors ............................................................... 66 Section 2-2: Sampling Theory ......................................................................................................73 The Need for a Sample-and-Hold Amplifi er (SHA) Function ........................................................ 74 The Nyquist Criteria ........................................................................................................................ 76 Baseband Antialiasing Filters .......................................................................................................... 78 Undersampling (Harmonic Sampling, Bandpass Sampling, IF Sampling, Direct IF-to-Digital Conversion) ................................................................................................. 80 Antialiasing Filters in Undersampling Applications ....................................................................... 81 Section 2-3: Data Converter AC Errors ........................................................................................83 Theoretical Quantization Noise of an Ideal N-Bit Converter .......................................................... 83 Noise in Practical ADCs .................................................................................................................. 88 Equivalent Input Referred Noise .................................................................................................... 89 Noise-Free (Flicker-Free) Code Resolution ................................................................................... 89 Dynamic Performance of Data Converters ...................................................................................... 90 Integral and Differential Nonlinearity Distortion Effects ................................................................ 90 Harmonic Distortion, Worst Harmonic, Total Harmonic Distortion (THD), Total Harmonic Distortion Plus Noise (THD + N) ...................................................................... 91 Signal-to-Noise-and-Distortion Ratio (SINAD), Signal-to-Noise Ratio (SNR), and Effective Number of Bits (ENOB) ....................................................................................... 91 Analog Bandwidth ........................................................................................................................... 92 Spurious Free Dynamic Range (SFDR) .......................................................................................... 93 Two-Tone Intermodulation Distortion (IMD) ................................................................................. 94 Second- and Third-Order Intercept Points, 1 dB Compression Point ............................................. 95 Multitone Spurious Free Dynamic Range ....................................................................................... 96 Wideband CDMA (WCDMA) Adjacent Channel Power Ratio (ACPR) and Adjacent Channel Leakage Ratio (ADLR) ................................................................................................. 97 Noise Power Ratio (NPR) ................................................................................................................ 98 Noise Factor (F) and Noise Figure (NF) ....................................................................................... 100 Aperture Time, Aperture Delay Time, and Aperture Jitter ........................................................... 106 A Simple Equation for the Total SNR of an ADC ........................................................................ 108 ADC Transient Response and Overvoltage Recovery ................................................................... 109 ADC Sparkle Codes, Metastable States, and Bit Error Rate (BER) ............................................. 111 DAC Dynamic Performance ......................................................................................................... 115 DAC Settling Time ................................................................................................................. 115 Glitch Impulse Area ............................................................................................................... 116 DAC SFDR and SNR ............................................................................................................. 117 Measuring DAC SNR with an Analog Spectrum Analyzer .................................................... 118 DAC Output Spectrum and sin (x)/x Frequency Roll-off ....................................................... 119 Oversampling Interpolating DACs ......................................................................................... 120 Section 2-4: General Data Converter Specifi cations ......................................................................123 Overall Considerations .................................................................................................................. 123 Logic Interface Issues .................................................................................................................... 124 Data Converter Logic: Timing and other Issues ............................................................................ 125 Section 2-5: Defi ning the Specifi cations .......................................................................................127 TLFeBOOKvii Contents Chapter 3: Data Converter Architectures ............................................................................147 Section 3-1: DAC Architectures .................................................................................................147 DAC Output Considerations .......................................................................................................... 148 Basic DAC Structures .................................................................................................................... 149 The Kelvin Divider (String DAC) .......................................................................................... 149 Thermometer (Fully-Decoded) DACs .................................................................................... 151 Binary-Weighted DACs .......................................................................................................... 153 R-2R DACs ............................................................................................................................. 155 Segmented DACs .................................................................................................................... 159 Oversampling Interpolating DACs ................................................................................................ 163 Multiplying DACs ......................................................................................................................... 164 Intentionally Nonlinear DACs ....................................................................................................... 164 Counting, Pulsewidth-Modulated (PWM) DACs .......................................................................... 167 Cyclic Serial DACs ........................................................................................................................ 167 Other Low Distortion Architectures .............................................................................................. 169 DAC Logic Considerations ............................................................................................................ 170 Section 3-2: ADC Architectures .................................................................................................175 The Comparator: A 1-Bit ADC ...................................................................................................... 178 High Speed ADC Architectures ..................................................................................................... 180 Flash Converters ..................................................................................................................... 180 Successive Approximation ADCs ........................................................................................... 185 Subranging, Error Corrected, and Pipelined ADCs ............................................................... 190 Serial Bit-Per-Stage Binary and Gray Coded (Folding) ADCs ............................................. 203 Counting and Integrating ADC Architectures ............................................................................... 211 A. H. Reeves’ 5-Bit Counting ADC ....................................................................................... 211 Charge Run-Down ADC ......................................................................................................... 212 Ramp Run-Up ADC ............................................................................................................... 212 Tracking ADC ........................................................................................................................ 213 Voltage-to-Frequency Converters (VFCs) .............................................................................. 214 Dual Slope/Multislope ADCs ................................................................................................. 218 Optical Converters ......................................................................................................................... 220 Resolver-to-Digital Converters (RDCs) and Synchros .................................................................. 221 Section 3-3: Sigma-Delta Converters ..........................................................................................231 Historical Perspective .................................................................................................................... 231 Sigma-Delta (Σ-∆) or Delta-Sigma (∆-Σ)? ................................................................................... 234 Basics of Sigma-Delta ADCs ........................................................................................................ 235 Idle Tone Considerations ............................................................................................................... 240 Higher Order Loop Considerations ............................................................................................... 241 Multibit Sigma-Delta Converters .................................................................................................. 242 Digital Filter Implications ............................................................................................................. 243 Multistage Noise Shaping (MASH) Sigma-Delta Converters ....................................................... 244 High Resolution Measurement Sigma-Delta ADCs ...................................................................... 245 Sigma-Delta DACs ........................................................................................................................ 249 Chapter 4: Data Converter Process Technology ....................................................................257 Section 4-1: Early Processes ......................................................................................................257 Vacuum Tube Data Converters ...................................................................................................... 257 TLFeBOOKviii Contents Solid State, Modular, and Hybrid Data Converters ....................................................................... 259 Calibration Processes ..................................................................................................................... 262 Section 4-2: Modern Processes ...................................................................................................265 Bipolar Processes ........................................................................................................................... 265 Thin Film Resistor Processes ........................................................................................................ 265 Complementary Bipolar (CB) Processes ....................................................................................... 266 CMOS Processes ........................................................................................................................... 266 Data Converter Processes and Architectures ................................................................................. 268 Section 4-3: Smart Partitioning .................................................................................................273 When Complete Integration Isn’t the Optimal Solution ................................................................ 273 Why Smart Partitioning is Necessary ........................................................................................... 276 What’s Changing? ......................................................................................................................... 277 Chapter 5: Testing Data Converters ...................................................................................283 Section 5-1: Testing DACs ........................................................................................................283 Static DAC Testing ........................................................................................................................ 283 End-Point Errors ..................................................................................................................... 284 Linearity Errors ...................................................................................................................... 286 Superposition and DAC Errors ............................................................................................... 286 Measuring DAC DNL and INL Using Superposition ............................................................ 287 Measuring DAC INL and DNL Where Superposition Does Not Hold .................................. 290 Testing DACs for Dynamic Performance ...................................................................................... 292 Settling Time .......................................................................................................................... 292 Glitch Impulse Area ............................................................................................................... 293 Oscilloscope Measurement of Settling Time and Glitch Impulse Area ................................ 294 Distortion Measurements ....................................................................................................... 295 Section 5-2: Testing ADCs ........................................................................................................303 A Brief Historical Overview of Data Converter Specifi cations and Testing ................................. 303 Static ADC Testing ........................................................................................................................ 304 Back-to-Back Static ADC Testing .......................................................................................... 306 Crossplot Measurements of ADC Linearity ........................................................................... 309 Servo-Loop Code Transition Test ........................................................................................... 310 Computer-Based Servo-Loop ADC Tester ............................................................................. 311 Histogram (Code Density) Test with Linear Ramp Input ...................................................... 312 Dynamic ADC Testing ................................................................................................................... 317 Manual “Back-to-Back” Dynamic ADC Testing ................................................................... 317 Measuring Effective Number of Bits (ENOB) Using Sinewave Curve Fitting ...................... 320 FFT Basics .............................................................................................................................. 322 FFT Test Setup Confi guration and Measurements ................................................................. 329 Verifying the FFT Accuracy ................................................................................................... 335 Generating Low Distortion Sinewave Inputs ......................................................................... 335 Noise Power Ratio (NPR) Testing .......................................................................................... 337 Measuring ADC Aperture Jitter Using the Locked-Histogram Test Method ......................... 338 Measuring Aperture Delay Time ............................................................................................ 340 Measuring ADC Aperture Jitter Using FFTs .......................................................................... 340 Measuring ADC Analog Bandwidth Using FFTs .................................................................. 342 Settling Time .......................................................................................................................... 343 TLFeBOOKix Contents Overvoltage Recovery Time ................................................................................................... 344 Video Testing, Differential Gain and Differential Phase ........................................................ 344 Bit Error Rate (BER) Tests ..................................................................................................... 348 Chapter 6: Interfacing to Data Converters ...........................................................................359 Section 6-1: Driving ADC Analog Inputs .....................................................................................359 Amplifer DC and AC Performance Considerations ...................................................................... 361 Rail-Rail Input Stages .................................................................................................................... 362 Output Stages ................................................................................................................................. 365 Gain and Level-Shifting Circuits Using Op Amps ........................................................................ 367 Op Amp AC Specifi cations and Data Converter Requirements .................................................... 369 Driving High Resolution Σ-∆ Measurement ADCs ....................................................................... 371 Driving Single-Ended Input Single-Supply 1.6 V to 3.6 V Successive Approximation ADCs ..... 372 Driving Single-Supply ADCs with Scaled Inputs ......................................................................... 373 Driving Differential Input CMOS Switched Capacitor ADCs ...................................................... 374 Single-Ended Drive Circuits for Differential Input CMOS ADCs ................................................ 376 Differential Input ADC Drivers ..................................................................................................... 378 Driving ADCs with Differential Amplifi ers .................................................................................. 382 Dual Op Amp Drivers .................................................................................................................... 383 Fully Integrated Differential Amplifi er Drivers ............................................................................. 384 Driving Differential Input ADCs with Integrated Differential Drivers ......................................... 387 Section 6-2: ADC and DAC Digital Interfaces(and Related Issues) ................................................397 Power-On Initialization of Data Converters ................................................................................. 397 Initialization of Data Converter Internal Control Registers ........................................................... 398 Low Power, Sleep, and Standby Modes ....................................................................................... 398 Single-Shot Mode, Burst Mode, and Minimum Sampling Frequency .......................................... 399 ADC Digital Output Interfaces ...................................................................................................... 400 ADC Serial Output Interfaces ....................................................................................................... 400 ADC Serial Interface to DSPs ...................................................................................................... 403 ADC Parallel Output Interfaces ..................................................................................................... 405 DAC Digital Input Interfaces ......................................................................................................... 408 DAC Serial Input Interfaces to DSPs ............................................................................................ 410 DAC Parallel Input Interfaces to DSPs .......................................................................................... 411 Section 6-3: Buffering DAC Analog Outputs ...............................................................................415 Differential to Single-Ended Conversion Techniques ................................................................... 416 Single-Ended Current-to-Voltage Conversion ............................................................................... 418 Differential Current-to-Differential Voltage Conversion ............................................................... 420 An Active Low-Pass Filter for Audio DAC .................................................................................. 420 Section 6-4: Data Converter Voltage References ..........................................................................423 Section 6-5: Sampling Clock Generation .....................................................................................427 Oscillator Phase Noise and Jitter ................................................................................................... 430 “Hybrid” Clock Generators ........................................................................................................... 437 Driving Differential Sampling Clock Inputs ................................................................................. 438 Sampling Clock Summary ............................................................................................................. 439 Chapter 7: Data Converter Support Circuits ........................................................................443 Section 7-1: Voltage References .................................................................................................443 Precision Voltage References ........................................................................................................ 443 TLFeBOOKx Contents Types of Voltage References .......................................................................................................... 444 Bandgap References ............................................................................................................... 446 Buried Zener References ........................................................................................................ 451 XFET References ................................................................................................................... 452 Voltage Reference Specifi cations .................................................................................................. 455 Tolerance ................................................................................................................................ 455 Drift ........................................................................................................................................ 455 Supply Range ......................................................................................................................... 456 Load Sensitivity ...................................................................................................................... 456 Line Sensitivity ....................................................................................................................... 457 Noise ....................................................................................................................................... 457 Scaled References .......................................................................................................................... 459 Voltage Reference Pulse Current Response ................................................................................... 460 Low Noise References for High Resolution Converters ............................................................... 462 Section 7-2: Low Dropout Linear Regulators ...............................................................................465 Linear Voltage Regulator Basics .................................................................................................... 465 Pass Devices and their Associated Trade Offs ............................................................................... 468 Low Dropout Regulator Architectures .......................................................................................... 472 The anyCAP Low Dropout Regulator Family ............................................................................... 475 Design Features Related to DC Performance ......................................................................... 475 Design Features Related to AC Performance ......................................................................... 476 A Basic Pole-Splitting Topology ............................................................................................ 477 The anyCAP Pole-Splitting Topology .................................................................................... 477 The anyCAP LDO series devices ........................................................................................... 478 Functional Diagram and Basic 50 mA LDO Regulator ......................................................... 479 LDO Regulator Thermal Considerations ............................................................................... 481 LDO Regulator Controllers ........................................................................................................... 485 Regulator Controller Differences ........................................................................................... 485 A Basic 5 V/1 A LDO Regulator Controller .......................................................................... 486 Selecting the Pass Device ....................................................................................................... 487 Thermal Design ...................................................................................................................... 488 Sensing Resistors for LDO Controllers .................................................................................. 489 PCB Layout Issues ................................................................................................................. 490 A 2.8 V/8 A LDO Regulator Controller ................................................................................. 491 Section 7-3: Analog Switches and Multiplexers ............................................................................493 CMOS Switch Basics .................................................................................................................... 494 Error Sources in the CMOS Switch ............................................................................................... 496 Applying the Analog Switch ........................................................................................................ 504 1 GHz CMOS Switches ................................................................................................................. 508 Video Switches and Multiplexers .................................................................................................. 508 Video Crosspoint Switches ............................................................................................................ 511 Digital Crosspoint Switches .......................................................................................................... 512 Switch and Multiplexer Families from Analog Devices ................................................................ 512 Parasitic Latchup in CMOS Switches and Muxes ......................................................................... 512 Section 7-4: Sample-and-Hold Circuits ........................................................................................519 Introduction and Historical Perspective ........................................................................................ 519 TLFeBOOKxi Contents Basic SHA Operation .................................................................................................................... 521 Track Mode Specifi cations ............................................................................................................ 522 Track-to-Hold Mode Specifi cations .............................................................................................. 522 Hold Mode Specifi cations ............................................................................................................. 526 Hold-to-Track Transition Specifi cations ....................................................................................... 528 SHA Architectures ......................................................................................................................... 529 Internal SHA Circuits for IC ADCs ............................................................................................... 531 SHA Applications .......................................................................................................................... 533 Chapter 8: Data Converter Applications .............................................................................539 Section 8-1: Precision Measurement and Sensor Conditioning ........................................................539 Applications of Precision Measurement Σ-∆ ADCs ...................................................................... 540 Weigh Scale Design Analysis Using the AD7730 ADC ................................................................ 544 Thermocouple Conditioning Using the AD7793 ........................................................................... 549 Direct Digital Temperature Measurements .................................................................................... 551 Microprocessor Substrate Temperature Sensors ............................................................................ 555 Applications of ADCs in Power Meters ........................................................................................ 558 Section 8-2: Multichannel Data Acquisition Systems .....................................................................563 Data Acquisition System Confi gurations ....................................................................................... 563 Multiplexing .................................................................................................................................. 564 Filtering Considerations in Data Acquisition Systems .................................................................. 567 Complete Data Acquisition Systems on a Chip ............................................................................. 568 Multiplexing Inputs to Σ-∆ ADCs ................................................................................................. 570 Simultaneous Sampling Systems ................................................................................................... 572 Data Distribution Systems ............................................................................................................ 574 Data Distribution Using an Infi nite Sample-and-Hold .................................................................. 578 Section 8-3: Digital Potentiometers ............................................................................................581 Modern Digital Potentiometers in Tiny Packages ......................................................................... 582 Digital Potentiometers with Nonvolatile Memory ........................................................................ 584 One-Time Programmable (OTP) Digital Potentiometers .............................................................. 585 Digital Potentiometer AC Considerations ..................................................................................... 586 Application Examples ................................................................................................................... 587 Section 8-4: Digital Audio .........................................................................................................591 Sampling Rate and THD + N Requirements for Digital Audio ..................................................... 592 Overall Trends in Digital Audio ADCs and DACs ........................................................................ 595 Voiceband Codecs .......................................................................................................................... 596 High Performance Audio ADCs and DACs in Separate Packages ................................................ 597 High Performance Multichannel Audio Codecs and DACs .......................................................... 600 Sample Rate Converters ................................................................................................................ 602 Section 8-5: Digital Video and Display Electronics .......................................................................607 Digital Video .................................................................................................................................. 607 Digital Video Formats ............................................................................................................ 608 Serial Data Interfaces ............................................................................................................. 612 Digital Video ADCs and DACs: Decoders, and Encoders ..................................................... 612 Specifi cations for Video Decoders and Encoders ................................................................... 614 Display Electronics ........................................................................................................................ 615 Flat Panel Display Electronics ............................................................................................... 619 TLFeBOOKxii Contents CCD Imaging Electronics ...................................................................................................... 622 Touchscreen Digitizers ........................................................................................................... 627 Section 8-6: Software Radio and IF Sampling ..............................................................................633 Evolution of Software Radio ......................................................................................................... 634 A Receiver Using Digital Processing at Baseband ........................................................................ 635 Narrowband IF-Sampling Digital Receivers ................................................................................. 636 Wideband IF-Sampling Digital Receivers ..................................................................................... 639 Increasing ADC Dynamic Range Using Dither ............................................................................. 649 Wideband Radio Transmitter Considerations ................................................................................ 655 Cellular Telephone Handsets ......................................................................................................... 659 The Role of ADCs and DACs in Cellular Telephone Handsets ..................................................... 661 SoftFone® and Othello Radio Chipsets from Analog Devices ..................................................... 662 Time-Interleaved IF Sampling ADCs with Digital Post-Processors ............................................. 667 Advanced Digital Post Processing ................................................................................................. 671 Advanced Filter Bank (AFB) ........................................................................................................ 672 AFB Design Example: The AD12400 12-Bit, 400 MSPS ADC ................................................... 673 Section 8-7: Direct Digital Synthesis (DDS) ................................................................................677 Introduction to DDS ...................................................................................................................... 677 Aliasing in DDS Systems .............................................................................................................. 681 Frequency Planning in DDS Systems ............................................................................................ 682 Modern Integrated DDS Systems .................................................................................................. 684 Section 8-8: Precision Analog Microcontrollers ............................................................................693 Characteristics of the MicroConverter Product Family ................................................................. 694 Some Σ-∆ MicroConverter Applications ....................................................................................... 700 ADuC7xxx MicroConverter Products Based on the ARM7 Processor Core ................................ 702 Chapter 9: Hardware Design Techniques .............................................................................709 Section 9-1: Passive Components ...............................................................................................711 Capacitors ...................................................................................................................................... 711 Dielectric Absorption ............................................................................................................. 712 Capacitor Parasitics and Dissipation Factor ........................................................................... 714 Tolerance, Temperature, and Other Effects ............................................................................ 715 Assemble Critical Components Last ...................................................................................... 715 Resistors and Potentiometers ......................................................................................................... 718 Resistor Parasitics ................................................................................................................... 720 Thermoelectric Effects ........................................................................................................... 720 Voltage Sensitivity, Failure Mechanisms, and Aging ............................................................. 722 Resistor Excess Noise ............................................................................................................ 723 Potentiometers ........................................................................................................................ 723 Inductance ...................................................................................................................................... 725 Stray Inductance ..................................................................................................................... 725 Mutual Inductance .................................................................................................................. 725 Ringing ................................................................................................................................... 728 Parasitic Effects in Inductors .................................................................................................. 728 Q or “Quality Factor” ............................................................................................................. 729 Don’t Overlook Anything .............................................................................................................. 729 TLFeBOOKxiii Contents Section 9-2: PC Board Design Issues ..........................................................................................733 Resistance of Conductors .............................................................................................................. 733 Voltage Drop in Signal Leads—“Kelvin” Feedback ..................................................................... 735 Signal Return Currents .................................................................................................................. 736 Grounding in Mixed Analog/Digital Systems ............................................................................... 737 Ground and Power Planes ...................................................................................................... 738 Double-Sided versus Multilayer Printed Circuit Boards ........................................................ 739 Multicard Mixed-Signal Systems ........................................................................................... 740 Separating Analog and Digital Grounds ................................................................................. 740 Grounding and Decoupling Mixed-Signal ICs with Low Digital Currents ........................... 742 Treat the ADC Digital Outputs with Care .............................................................................. 743 Sampling Clock Considerations ............................................................................................. 744 The Origins of the Confusion about Mixed-Signal Grounding: Applying Single-Card Grounding Concepts to Multicard Systems ...................................................................... 746 Summary: Grounding Mixed-Signal Devices with Low Digital Currents in a Multicard System ............................................................................................................... 747 Summary: Grounding Mixed-Signal Devices with High Digital Currents in a Multicard System ............................................................................................................... 748 Grounding DSPs with Internal Phase-Locked Loops ............................................................. 748 Grounding Summary .............................................................................................................. 749 Some General PC Board Layout Guidelines for Mixed-Signal Systems ...................................... 750 Skin Effect .............................................................................................................................. 751 Transmission Lines ................................................................................................................. 753 Be Careful With Ground Plane Breaks ................................................................................... 753 Ground Isolation Techniques .................................................................................................. 754 Static PCB Effects .................................................................................................................. 756 Sample MINIDIP and SOIC Op Amp PCB Guard Layouts .................................................. 758 Dynamic PCB Effects ............................................................................................................ 760 Stray Capacitance ................................................................................................................... 761 Capacitive Noise and Faraday Shields ................................................................................... 762 The Floating Shield Problem .................................................................................................. 762 Buffering ADCs Against Logic Noise ................................................................................... 763 Section 9-3: Analog Power Supply Systems ..................................................................................767 Linear IC Regulation ..................................................................................................................... 768 Some Linear Voltage Regulator Basics .................................................................................. 768 Pass Devices .......................................................................................................................... 770 ±15 V Regulator Using Adjustable Voltage ICs ..................................................................... 770 Low Dropout Regulator Architectures ................................................................................... 771 Fixed-Voltage, 50/100/200/500/1000/1500 mA LDO Regulators ......................................... 772 Adjustable Voltage, 200 mA LDO Regulator ......................................................................... 774 Charge-Pump Voltage Converters ................................................................................................. 775 Regulated Output Charge-Pump Voltage Converters .................................................................... 776 Linear Post Regulator for Switching Supplies .............................................................................. 778 Grounding Linear and Switching Regulators ................................................................................ 779 Power Supply Noise Reduction and Filtering ............................................................................... 782 Capacitors ............................................................................................................................... 782 TLFeBOOKxiv Contents Ferrites .................................................................................................................................... 786 Card Entry Filter ..................................................................................................................... 787 Rail Bypass/Distribution Filter ............................................................................................... 788 Local High Frequency Bypass/Decoupling ............................................................................ 789 Section 9-4: Overvoltage Protection ...........................................................................................793 In-Circuit Overvoltage Protection ................................................................................................. 793 General Input Common Mode Limitations ................................................................................... 793 Clamping Diode Leakage .............................................................................................................. 795 A Flexible Voltage Follower Protection Circuit ........................................................................... 796 Common-Mode Overvoltage Protection Using CMOS Channel Protectors ................................. 797 CM Overvoltage Protection Using High CM Voltage In Amp ...................................................... 798 Inverting Mode Op Amp Protection Schemes ............................................................................... 800 Amplifi er Output Voltage Phase-Reversal ..................................................................................... 800 An Output Phase-Reversal Do-it-Yourself Test ...................................................................... 802 Fixes for Output Phase–Reversal ........................................................................................... 802 Input Differential Protection ......................................................................................................... 803 Protecting In Amps Against Overvoltage ...................................................................................... 804 Overvoltage Protection Using CMOS Channel Protectors ............................................................ 808 Digital Isolators ............................................................................................................................. 810 Out-of-Circuit Overvoltage Protection .......................................................................................... 813 ESD Models and Testing ............................................................................................................... 817 Section 9-5: Thermal Management .............................................................................................823 Thermal Basics .............................................................................................................................. 823 Heat Sinking .................................................................................................................................. 825 Data Converter Thermal Considerations ....................................................................................... 829 Section 9-6: EMI/RFI Considerations .........................................................................................833 EMI/RFI Mechanisms ................................................................................................................... 834 EMI Noise Sources ........................................................................................................................ 834 EMI Coupling Paths ...................................................................................................................... 834 Noise Coupling Mechanisms ......................................................................................................... 834 Reducing Common-Impedance Noise ........................................................................................... 835 Noise Induced by Near-Field Interference .................................................................................... 836 Reducing Capacitance-Coupled Noise .......................................................................................... 836 Reducing Magnetically-Coupled Noise ........................................................................................ 837 Passive Components: Your Arsenal Against EMI .......................................................................... 838 Reducing System Susceptibility to EMI ........................................................................................ 839 A Review of Shielding Concepts ................................................................................................... 839 General Points on Cables and Shields ........................................................................................... 842 Input-Stage RFI Rectifi cation Sensitivity ...................................................................................... 846 Background: Op Amp and In Amp RFI Rectifi cation Sensitivity Tests ................................. 846 An Analytical Approach: BJT RFI Rectifi cation .................................................................... 847 An Analytical Approach: FET RFI Rectifi cation .................................................................. 848 Reducing RFI Rectifi cation Within Op amp and In Amp Circuits ......................................... 849 Op Amp Inputs ............................................................................................................................. 849 In Amp Inputs ................................................................................................................................ 850 Amplifi er Outputs and EMI/RFI ................................................................................................... 852 TLFeBOOKxv Contents Printed Circuit Board Design for EMI/RFI Protection .................................................................. 852 Choose Logic Devices Carefully .................................................................................................. 853 Design PCBs Thoughtfully ............................................................................................................ 853 Designing Controlled Impedances Traces on PCBs ..................................................................... 854 Microstrip PCB Transmission Lines ............................................................................................. 855 Some Microstrip Guidelines .......................................................................................................... 855 Symmetric Stripline PCB Transmission Lines .............................................................................. 856 Some Pros and Cons of Embedding Traces ................................................................................... 857 Dealing with High-Speed Logic .................................................................................................... 858 Section 9-7: Low Voltage Logic Interfacing ..................................................................................867 Voltage Tolerance and Voltage Compliance .................................................................................. 870 Interfacing 5 V Systems to 3.3 V Systems using NMOS FET “Bus Switches” ............................ 871 3.3 V/2.5 V Interfaces .................................................................................................................... 873 3.3 V/2.5 V, 3.3 V/1.8 V, 2.5 V/1.8 V Interfaces ............................................................................ 874 Hot Swap and Hot Plug Applications of Bus Switches ................................................................. 878 Internally Created Voltage Tolerance / Compliance ...................................................................... 879 Section 9-8: Breadboarding and Prototyping ...............................................................................881 “Deadbug” Prototyping ................................................................................................................. 882 Solder-Mount Prototyping ............................................................................................................. 884 Milled PCB Prototyping ................................................................................................................ 885 Beware of Sockets ......................................................................................................................... 886 Some Additional Prototyping Points ............................................................................................. 887 Evaluation Boards .......................................................................................................................... 887 General-Purpose Op Amp Evaluation Board from the Mid-1990s ........................................ 888 Dedicated Op Amp Evaluation Boards .................................................................................. 888 Data Converter Evaluation Boards ......................................................................................... 890 Index ...............................................................................................................................895