Practical Shielding, EMC/EMI, Noise Reduction, Earthing and Circuit Board Layout

Transcription

1 Practical Shielding, EMC/EMI, Noise Reduction, Earthing and Circuit Board Layout Contents 1 Introduction Introduction EMI vs EMC Interference sources Need for standards EMC the issues Electromagnetic disturbances EMC testing categories The compatibility gap Emission, immunity and compatibility Causes and consequences of EMI Levels of compliance and EMC engineering application 12 2 EM principles Introduction Coupling paths: sources and victims Coupling mechanisms Coupling via the supply network Electromagnetic fields Rayleigh/Maxwell near/far fields Coupling modes Radiated emissions from PCB (differential mode) Cable radiated emissions (common mode) Coupling paths (conducted emissions) Susceptibility to radiated field coupling Transient sources Automotive transients Supply voltage phenomenon 30

2 3 EM principles Introduction DM/CM conversion Common mode rejection ratio (CMRR) Units in EMC engineering Spectrum usage and created Interference Fourier analysis Choice of logic family Lightning and ESD bandwidth 39 4 Shielding Introduction Shielding and Murphy s Law LF magnetic shielding Apertures and shielding effectiveness Waveguides Gasketting and sealing Panel displays and keyboards Ventilation and shielding PCB-level shielding 49 5 Grounding Introduction Earth and safety ground Grounding and frequency Ground loops Ground impedance Ground topologies Guidelines for grounding 57 6 Cables and connectors Introduction Cables in context Cable parameters and implication Cable types and frequency Cable routing and screening Types of screening 66

3 6.7 Screened and unscreened connectors Transmission lines Cable coupling to radiated field Useful references 71 7 Circuits and components Introduction Parasitic in passives Clocking Choice of logic family Design and component choice Analog immunity and demodulation 76 8 Protection and filtering Introduction Filter types and operation Soft ferrites Thumb rules Filter specifications Impedance matching Filtering precision and Filter earthing Filters and shielding Surge protection devices (SPDs) Surge protection and data integrity Surge protection ratings Surge protection fusing Positioning SPDs Electrostatic discharge Creepage and clearance Shielding Signal line protection 97 9 Engineering measurements Introduction Bench and test laboratory Determining common mode noise Field probes Common mode and Differential mode currents 105

4 10 Power supplies Introduction PSUs as noise generators Switch-mode PSU as a noise generator Coupling paths, conducted emissions Power supplies Parasitic components in SMPS Effects of diodes Improvements from inductors The mains filter PSU threats PCB design and layout Introduction Levels of EMC Engineering Application PCB design objectives Differential mode coupling Common mode coupling Electrical and physical parameters Board layout Component and track layout Areas under control vs outside Reference planes The Image Plane effect Maintaining plane integrity and gridded ground Board layering Layer stacking Grounding on the board V Chassis Connection Decoupling Capacitors Transmission Lines on PCBs Transmission line termination Multiple boards and backplanes Interfacing noisy and quite areas 136

5 12 EMC engineering management Introduction Why manage EMC? Wait and its too late How to manage EMC Levels of compliance EMC lifecycle Life-cycle flow chart EMC in context How much effort? Co-ordinating efforts Design practices EMC engineering implementation Project management Need for control plan Test plans Test reports (immunity) Test and calibration of facilities Maintaining EMC in production Conclusion Introduction EMC Legalities Tutorials Practical Exercises PowerPoint Slides 178