High-Speed PCB Design und EMV Minimierung

Transcription

1 TRAINING Bei dem hier beschriebenen Training handelt es sich um ein Cadence Standard Training. Sie erhalten eine Dokumentation in englischer Sprache. Die Trainingssprache ist deutsch, falls nicht anders angekündigt. High-Speed PCB Design und EMV Minimierung Overview Description The development of semiconductor technology has meant that fast edge speeds are now the norm for many standard digital device families, and their effects have to be considered in PCB design to maintain signal integrity, even at modest clock speeds. This unique course provides a fundamental first step in understanding and applying the principles of high-speed design to ensure signal integrity in PCBs, and gives participants a sound knowledge of basic techniques which they can apply immediately to benefit their designs. While EDA signal integrity tools are not required, this course provides an essential foundation necessary for successful application of such tools. The course is divided into three parts: Part 1 emphasizes the underlying physical principles of high speed PCB design issues and their application to realworld design projects. Application issues covered include controlling line impedance and cross-talk, the effects of power distribution, de-coupling, and the PCB layer structure. Part 2 focuses on the material properties of PCBs, highlighting the important parameters for high speed circuits (including relative cost and fabrication), and comparing these properties in a wide variety of available laminate materials. Part 3 applies the principles developed in Part 1 to EMI on the PCB, demonstrating the critical roles played by the PCB structure, components, IC packaging, interconnection and grounding in EMI generation and propagation. Since much of the material presented refers directly to the same physical principles developed earlier, this part of the course builds on and reinforces key concepts, in addition to providing practical guidance on EMI control. Uniquely, the course is liberally illustrated with examples and "what if" scenarios showing the effects of varying different parameters, enabling participants to develop an understanding of their relative importance and magnitude. Helpful guidelines on assessing and implementing best practice are included. Audience The course is suitable for: Digital design engineers who either have no experience of the background and methods required for high-speed PCB design, or who have some experience but would benefit from a more complete and in-depth knowledge of the topics presented. PCB designers working on digital boards where high-speed design rules are required. Prerequisites Participants should be familiar with basic electrical concepts. No prior knowledge of EDA design tools is required or assumed. Course Agenda Design Issues covered: The impact, issues and challenges of high-speed design The underlying basic physical principles essential for understanding the issues and how to treat them How power distribution plays a key role The need for track impedance control and how to achieve it How to control cross-talk between PCB tracks The essential features of ICs for high-speed design, and of basic device models

2 Strategies to realize nets and buses, with the merits of different routing and termination schemes How different PCB materials and layer stack-ups play a vital role The principles of EMI generation and why it has become a major issue EMI control at component level and at PCB level Day 1 The roles that signal routing, interconnection and grounding play in EMI (through tracks, planes, connectors, cables and back-planes), and strategies to control its propagation 1. Overview When is a design "high speed"? How industry drivers force high speed Signal integrity definition How high speeds challenge signal integrity High speed PCB design the issues 2. Fundamental electrical concepts Time and frequency - harmonic content of digital signal waveform Effective operating frequency Resistance, inductance and capacitance Transmission lines and wave propagation Current paths on a PCB return current Attenuation of signals on lines skin effect, loss tangent Coupling and cross-talk mutual capacitance and mutual inductance Parts placement effects 3. Power distribution Power requirements Coping with changing currents Board level de-coupling - limitations Component level de-coupling Day 2 De-coupling capacitors for high-speed devices Practical considerations for high-speed PCBs 4. Impedance control Transmission lines propagation delay, velocity, characteristic impedance Reflections from a terminated line positive and negative Source reflections Seite 2 von 5

3 Dielectric properties effective length and critical length Practical PCB transmission lines microstrip, embedded microstrip, stripline and dual stripline Proximity effects Differential pairs Characteristic impedance range limits Types of terminations and their effects 5. Cross-talk Capacitive and inductive cross-talk Dependence on edge rate Coupling factor Ground plane effects Forward and backward cross-talk Cross-talk control in PCB design parts, planes, tracks, connectors, terminations 6. Devices and models Device input/output characteristics Essential features of a device model Simple models Day 3 Real device models 7. Lines, loads and track routing Realizing nets and buses with lumped, distributed and radial lines Discontinuities reflections, critical length, connectors and vias Incident and reflected mode switching Overshoot and undershoot Effect of impedance and loading on signal propagation delay Load distribution and topology merits of different schemes General routing and termination considerations Connectors for high-speed systems 8. PCB structure Merits of different layer stacks number of layers, proximity of planes Fabrication considerations Process variables in PCB manufacture Seite 3 von 5

4 PCB materials electrical and mechanical considerations Board thickness and tolerance Impedance testing 9. Course summary The challenge of high-speed design Building design experience Applying techniques and tools - the next stages Day 4 - PCB materials for high-speed circuits 1. PCB material properties PCB material requirements for high-speed circuits Key laminate and cladding parameters FR-4 - the industry standard Epoxy fiberglass materials PTFE/ceramic materials Beyond FR-4 - routes to higher performance 2. Multilayer process Outline of multilayer process steps (including buried capacitance and microvias) Day 4 - Minimising EMI through PCB design 1. EMC control EMC concerns for designers Why EMI has become a major issue EMI mechanisms The five factors in EMI analysis EMI from digital systems what can we control? Worldwide regulatory requirements 2. Principles of EMI generation Electromagnetic wave propagation Near field and far field - the radiated signal Generation of RF fields on a PCB Differential mode and common mode current Differential mode and common mode radiation Seite 4 von 5

5 Day 5 - Minimising EMI through PCB design (cont d) 3. PCB structure Layer stacking in the PCB The 20-H rule Image planes RF current loops due to power and ground Grounding concepts and methods Electrically long tracks (l/20 rule) System partitioning multipoint grounding Ground plane integrity Via properties 4. Components and EMC IC packaging Ground bounce Lead capacitance EMC techniques for large heat sinks Power line filtering EMC control at component level 5. Connectivity and interconnection Split planes Power plane filtering PCB with split planes isolation and bridging Localized ground plane System interconnections connectors, cables and back-planes RF coupling PCB to PCB and PCB to cardcage Indirect multipoint grounding Back-plane connectors and signal routing 6. Review and summary Other EMC factors transmission lines, cross-talk, electrostatic discharge Review of EMI control principles Key areas for designers Seite 5 von 5