Electromagnetic Compatibility (EMC) Design and Test Case Analysis

JUNQI ZHENG, National Radio Interference and Standardization Technical Committee; Shanghai Testing and Inspection Institute for Electrical Equipment, China.

• Preface xiExordium xvIntroduction xix1 The EMC Basic Knowledge and the Essence of the EMC Test 11.1 What Is EMC? 11.2 Conduction, Radiation, and Transient 21.3 Theoretical Basis 41.3.1 Time Domain and Frequency Domain 41.3.2 The Concept of the Unit for Electromagnetic Disturbance, dB 51.3.3 The True Meaning of Decibel 61.3.4 Electric Field, Magnetic Field, and Antennas 91.3.5 Resonance of the RLC Circuit 171.4 Common Mode and Differential Mode in the EMC Domain 211.5 Essence of the EMC Test 231.5.1 Essence of the Radiated Emission Test 231.5.2 Essence of the Conducted Emission Test 251.5.3 Essence of the ESD Immunity Test 291.5.4 Essence of the Radiated Immunity Test 301.5.5 Essence of the Common‐Mode Conducted Immunity Test 321.5.6 Essence of the Differential‐Mode Conducted Immunity Test 341.5.7 Differential‐Mode and Common‐Mode Hybrid Conducted Immunity Test 352 Architecture, Shielding, and Grounding Versus EMC of the Product 372.1 Introduction 372.1.1 Architecture Versus EMC of the Product 372.1.2 Shielding Versus EMC of the Product 382.1.3 Grounding Versus EMC of the Product 402.2 Analyses of Related Cases 412.2.1 Case 1: The Conducted Disturbance and the Grounding 412.2.2 Case 2: The Ground Loop During the Conducted Emission Test 462.2.3 Case 3: Where the Radiated Emission Outside the Shield Comes From 492.2.4 Case 4: The “Floating” Metal and the Radiation 522.2.5 Case 5: Radiated Emission Caused by the Bolt Extended Outside the Shield 552.2.6 Case 6: The Compression Amount of the Shield and Its Shielding Effectiveness 592.2.7 Case 7: The EMI Suppression Effectiveness of the Shielding Layer Between the Transformer’s Primary Winding and Secondary Winding in the Switching‐Mode Power Supply 622.2.8 Case 8: Bad Contact of the Metallic Casing and System Reset 682.2.9 Case 9: ESD Discharge and the Screw 702.2.10 Case 10: Heatsink Also Affects the ESD Immunity 712.2.11 Case 11: How Grounding Benefits EMC Performance 722.2.12 Case 12: The Heatsink Shape Affects Conducted Emissions from the Power Ports 762.2.13 Case 13: The Metallic Casing Oppositely Causes the EMI Test Failed 822.2.14 Case 14: Whether Directly Connecting the PCB Reference Ground to the Metallic Casing Will Lead to ESD 882.2.15 Case 15: How to Interconnect the Digital Ground and the Analog Ground in the Digital‐Analog Mixed Devices 943 EMC Issues with Cables, Connectors, and Interface Circuits 1013.1 Introduction 1013.1.1 Cable Is the Weakest Link in the System 1013.1.2 The Interface Circuit Provides Solutions to the Cable Radiation Problem 1023.1.3 Connectors Are the Path Between the Interface Circuit and the Cable 1033.1.4 The Interconnection between the PCBs Is the Weakest Link of the Product EMC 1043.2 Analyses of Related Cases 1073.2.1 Case 16: The Excessive Radiation Caused by the Cabling 1073.2.2 Case 17: Impact from the Pigtail of the Shielded Cable 1103.2.3 Case 18: The Radiated Emission from the Grounding Cable 1133.2.4 Case 19: Is the Shielded Cable Clearly Better than the Unshielded Cable? 1173.2.5 Case 20: Impacts on ESD Immunity of the Plastic Shell Connectors and the Metallic Shell Connector 1243.2.6 Case 21: The Selection of the Plastic Shell Connector and the ESD Immunity 1263.2.7 Case 22: When the Shield Layer of the Shielded Cable Is Not Grounded 1283.2.8 Case 23: The Radiated Emission Problem Brings Out Two EMC Design Problems of a Digital Camera 1313.2.9 Case 24: Why PCB Interconnecting Ribbon Is So Important for EMC 1383.2.10 Case 25: Excessive Radiated Emission Caused by the Loop 1443.2.11 Case 26: Pay Attention to the Interconnection and Wiring Inside the Product 1493.2.12 Case 27: Consequences of the Mixed Wiring Between Signal Cable and Power Cable 1513.2.13 Case 28: What Should Be Noticed When Installing the Power Filters 1554 Filtering and Suppression for EMC Performance Improvement 1614.1 Introduction 1614.1.1 Filtering Components 1614.1.2 Surge Protection Components 1674.2 Analyses of Related Cases 1734.2.1 Case 29: The Radiated Emission Caused by a Hub Exceeds the Standard Limit 1734.2.2 Case 30: Installation of the Power Supply Filter and the Conducted Emission 1784.2.3 Case 31: Filtering the Output Port May Impact the Conducted Disturbance of the Input Port 1824.2.4 Case 32: Properly Using the Common‐Mode Inductor to Solve the Problem in the Radiated and Conducted Immunity Test 1874.2.5 Case 33: The Design of Differential‐Mode Filter for Switching‐Mode Power Supply 1904.2.6 Case 34: Design of the Common‐Mode Filter for Switching‐Mode Power Supply 1964.2.7 Case 35: Whether More Filtering Components Mean Better Filtering Effectiveness 2034.2.8 Case 36: The Events Should Be Noticed When Positioning the Filters 2084.2.9 Case 37: How to Solve Excessive Harmonic Currents of Switching‐Mode Power Supply 2114.2.10 Case 38: Protections from Resistors and TVSs on the Interface Circuit 2134.2.11 Case 39: Can the Surge Protection Components Be in Parallel Arbitrarily? 2184.2.12 Case 40: Components in Surge Protection Design Must Be Coordinated 2244.2.13 Case 41: The Lightning Protection Circuit Design and the Component Selections Must Be Careful 2264.2.14 Case 42: Strict Rule for Installing the Lightening Protections 2274.2.15 Case 43: How to Choose the Clamping Voltage and the Peak Power of TVS 2304.2.16 Case 44: Choose the Diode for Clamping or the TVS for Protection 2324.2.17 Case 45: Ferrite Ring Core and EFT/B Immunity 2354.2.18 Case 46: How Ferrite Bead Reduces the Radiated Emission of Switching‐Mode Power Supply 2385 Bypassing and Decoupling 2435.1 Introduction 2435.1.1 The Concept of Decoupling, Bypassing, and Energy Storage 2435.1.2 Resonance 2445.1.3 Impedance 2485.1.4 The Selection of Decoupling Capacitor and Bypass Capacitor 2495.1.5 Capacitor Paralleling 2515.2 Analyses of Related Cases 2535.2.1 Case 47: The Decoupling Effectiveness for the Power Supply and the Capacitance of Capacitor 2535.2.2 Case 48: Locations of the Ferrite Bead and Decoupling Capacitor Connected to the Chip’s Power Supply Pin 2585.2.3 Case 49: Producing Interference of the ESD Discharge 2635.2.4 Case 50: Using Small Capacitance Can Help Solve a Longstanding Problem 2665.2.5 Case 51: How to Deal with the ESD Air Discharge Point for the Product with Metallic Casing 2685.2.6 Case 52: ESD and Bypass Capacitor for Sensitive Signals 2705.2.7 Case 53: Problems Caused by the Inappropriate Positioning of the Magnetic Bead During Surge Test 2735.2.8 Case 54: The Role of the Bypass Capacitor 2755.2.9 Case 55: How to Connect the Digital Ground and the Analog Ground at Both Sides of the Opto‐Coupler 2785.2.10 Case 56: Diode and Energy Storage, the Immunity of Voltage Dip, and Voltage Interruption 2826 PCB Design and EMC 2896.1 Introduction 2896.1.1 PCB Is a Microcosm of a Complete Product 2896.1.2 Loops Are Everywhere in PCB 2896.1.3 Crosstalk Must Be Prevented 2906.1.4 There Are Many Antennas in the PCB 2916.1.5 The Impedance of the Ground Plane in PCB Directly Influences the Transient Immunity 2916.2 Analyses of Related Cases 2936.2.1 Case 57: The Role of “Quiet” Ground 2936.2.2 Case 58: The Loop Formed by PCB Routing Causes Product Reset During ESD Test 2986.2.3 Case 59: Unreasonable PCB Wiring Causes the Interface Damaged by Lightning Surge 3036.2.4 Case 60: How to Dispose the Grounds at Both Sides of Common‐Mode Inductor 3056.2.5 Case 61: Avoid Coupling When the Ground Plane and the Power Plane Are Poured on PCB 3096.2.6 Case 62: The Relationship Between the Width of PCB Trace and the Magnitude of the Surge Current 3146.2.7 Case 63: How to Avoid the Noise of the Oscillator Being Transmitted to the Cable Port 3176.2.8 Case 64: The Radiated Emission Caused by the Noise from the Address Lines 3196.2.9 Case 65: The Disturbance Produced by the Loop 3246.2.10 Case 66: The Spacing Between PCB Layers and EMI 3296.2.11 Case 67: Why the Sensitive Trace Routed at the Edge of the PCB Is Susceptible to the ESD Disturbance 3346.2.12 Case 68: EMC Test Can Be Passed by Reducing the Series Resistance on the Signal Line 3386.2.13 Case 69: Detailed Analysis Case for the PCB Design of Analog‐Digital Mixed Circuit 3396.2.14 Case 70: Why the Oscillator Cannot Be Placed on the Edge of the PCB 3576.2.15 Case 71: Why the Local Ground Plane Needs to Be Placed Under the Strong Radiator 3606.2.16 Case 72: The Routing of the Interface Circuit and the ESD Immunity 3637 Components, Software, and Frequency Jitter Technique 367 7.1 Components, Software, and EMC 3677.2 Frequency Jitter Technique and EMC 3687.3 Analyses of Related Cases 3687.3.1 Case 73: Effect on the System EMC Performance from the EMC Characteristics of the Component and Software Versus Cannot Be Ignored 3687.3.2 Case 74: Software and ESD Immunity 3717.3.3 Case 75: The Conducted Emission Problem Caused by Frequency Jitter Technique 3737.3.4 Case 76: The Problems of Circuit and Software Detected by Voltage Dip and Voltage Interruption Tests 379Appendix A EMC Terms 381Appendix B EMC Tests in Relevant Standard for Residential Product, Industrial, Scientific, and Medical Product, Railway Product, and Others 385Appendix C EMC Test for Automotive Electronic and Electrical Components 405Appendix D Military Standard Commonly Used for EMC Test 429Appendix E EMC Standards and Certification 455Further Reading 467Index 469