"We applied what we learnt ... to our next design and we got the cleanest set of signals we'd ever seen"

"We had rules but we didn't really understand them. The class made us realise WHY we had rules and, more importantly, when NOT to apply them."

Fast edge speeds are now the norm for many standard digital device families, and their effects have to be considered in PCB design to ensure signal integrity and minimise electromagnetic interference, even at modest clock speeds.

Many design teams have rules for PCB design, but do not understand why or when to apply these rules for the best possible results. This course explores, from basic physical principles, the key issues in high-speed PCB design and explains rules and guidelines for achieving signal integrity and minimal EMI.

This course breaks down into two parts:

Part one applies basic physical principles to develop an understanding of the key issues of high-speed design for signal integrity. These range from controlling reflections and crosstalk to the design of the power distribution system and the PCB layer structure.

The second part builds seamlessly on the principles and practice established in part one to develop techniques for design and test at frequencies above 1 GHz for Gb/s serial transmission and for controlling the generation and propagation of EMI at the PCB level. Key topics cover signal quality, material effects and EMC from components to backplanes.

Both parts of the course are liberally illustrated with examples and “what if” scenarios. These show, by simulation, the effects of varying different parameters, enabling participants to develop an understanding of their relative importance and magnitude.

The basic techniques developed can be applied immediately to improve PCB design, without the use of EDA signal integrity tools, but the course also provides a much needed foundation for understanding how to benefit from the use of such tools.

• Provide a sound knowledge of the fundamental concepts of PCB design.
• To teach you a toolkit of practical techniques which you can immediately apply to benefit your designs.
• To give you the knowledge to approach your PCB design project with confidence.
• To provide guidelines on assessing and implementing best practice.

5 days. This class can also be taken in two separate modules - High Speed PCB Design (3 days) and RF EMI Design (2 days).

Delegates should be familiar with basic electrical concepts. No prior knowledge of PCB design tools is required or assumed. As the course is built up from basic electrical principles it is suitable for engineers from many areas of application and experience, including new graduates.

This course is aimed at design engineers seeking in-depth knowledge of high-speed PCB design; signal integrity issues; high frequency effects and EMC. PCB designers working on digital or mixed signal boards with design rules governing track impedance control; line terminations and routing to minimise noise coupling etc. will also benefit from this course.

This course covers the following topics:-

• Signal waveforms, frequency components and risetime. Bandwidths of analog and digital signals. How capacitance and loop inductance on a PCB determine signal behaviour. Current paths on a PCB.
• Impedance control of the power distribution system. Controlling induced noise - decoupling networks, PCB planes and bandwidth requirements. Optimising power delivery.
• Track impedance, reflections, and line terminations. Effects of PCB structure, materials, geometry and fabrication. Track impedance testing.
• Coupled lines. Odd and even modes – differential and common mode currents. Differential transmission, routing and termination. Unwanted coupling – crosstalk. Near end and far end crosstalk, effects of coupled length, multiple lines.
• ICs for high-speed design. I/O characteristics, I/V curves, transition timing. Behavioural device models. IBIS standards.
• PCB routing topologies. Branching and non-branching topologies. Constraints. Discontinuity effects – connectors, vias, stubs etc. Equalisation, multiple capacitance loading and clock distribution.
• High frequency measurement and test – components and signal paths. Time domain (scope, TDR/TDT) and frequency domain (VNA, spectrum analyser). Probe bandwidth. S-parameters.
• Gb/s transmission on PCBs - application of transmission engineering methods. PCB track effects on signal quality (BER, ISI, jitter). Technologies (e.g LVDS, PCI Express). PCB requirements to meet system performance.
• Frequency-dependent PCB transmission lines. Waveform degradation due to conductor and dielectric loss. PCB material selection – frequency behaviour, manufacturing and cost tradeoffs, and criteria for acceptable signal performance.
• EMC control. EMI mechanisms – what factors can we control? Wave propagation, near and far field impedance. RF field generation on a PCB. Differential to common mode conversion and radiation.
• Controlling EMI generation on PCBs. Image planes, stackup, return currents. Grounding schemes, common impedance coupling, partitioning, split planes.
• EMI from components to systems. IC package parasitics, ground bounce, component level effects. Filtering, isolation and bridging on PCBs. Interconnections, cables, backplanes, signal routing.

Part 1: Essential High-speed PCB Design for Signal Integrity

Module 1 - High-speed design overview

• Design issues
• When is a design “high speed”?
• Industry drivers forcing high speed
• Signal integrity and the high speed challenge
• Wave propagation and wave properties
• The PCB contribution
• Key requirements for high speed PCB design

Module 2 - Fundamental electrical concepts

• Time domain and frequency domain
• Analog and digital signal bandwidth
• Digital waveforms
• Clock speed versus edge speed (risetime)
• Effective operating frequency and knee frequency
• Current, voltage and resistance
• Electric fields, capacitance and dielectric constant
• Magnetic fields and inductance
• Effect of circuit components on signal waveform
• Current paths on a PCB
• Attenuation of signals on lines

Module 3 - Power delivery

• Power requirements
• Coping with changing currents and induced noise
• Board level and component level decoupling
• Practical limitations
• Three problems with the traditional approach to decoupling
• Expected versus actual response of decoupling networks
• The alternative approach to power delivery
• Flattening the impedance response
• Component current risetimes
• Ground plane resonance
• Two approaches to power delivery

Module 4 - PCB transmission lines

• Transmission line velocity and delay
• Characteristic impedance
• Material and stackup effects
• Geometry and fabrication effects
• Propagation of a voltage step
• Transmission line input impedance
• Reflection from a terminated line
• Impedance control by line termination
• Series and parallel termination

Module 5 - differential transmission

• Why use differential transmission?
• Differential signalling
• Effects of equal and unequal transmission line lengths
• Differential and common mode currents
• Routing differential tracks close together
• Coupled lines (odd and even mode)
• Rules for routing differential transmission lines
• Line terminations

Module 6 – Crosstalk

• Capacitive and inductive crosstalk
• Dependence on edge rate
• Solid ground planes
• Forward and backward crosstalk
• Where do the coupled signals go?
• Near end and far end crosstalk
• Effect of coupled length
• Other coupling and ground plane effects
• Crosstalk from multiple lines
• Crosstalk induced jitter
• Crosstalk control in PCB design

Module 7 – Modelling drivers and receivers

• IC device characteristics
• Simple equivalent circuits and models
• Modelling input, output and I/O ports in real devices
• Behavioural device model
• IBIS (I/O Buffer Information Specification)
• Measuring and extracting I-V curves
• Transient characteristics and transition timing
• IBIS standards

Module 8 - PCB routing topologies

• Transmission line types, nets and buses
• Track routing effects
• Discontinuity effects
• Serpentine tracks (delay equalisation)
• Incident and reflected mode switching
• Overshoot and ringing
• Topology types
• Multiple capacitance loading
• Clock distribution
• General principles for routing

Module 9 - PCB structure, manufacture and measurement

• Layer stacking effects and principles
• Effects of PCB fabrication process variables on high-speed designs
• The influence of key PCB materials parameters
• Measurement of transmission line impedance
• TDR testing of PCB track impedance

Part 2: High-speed PCB Design for Gigabit Data Rates and EMI Control

Module 10 - What is “high-speed”? - Part II

• Trends in design and technology
• How do we measure and test?
• Time domain
• Frequency domain
• What do we measure (components/system path) ?

Module 11 - Gb/s transmission on PCBs

• Lessons on signal quality from telecommunications digital transmission
• Serialiser/Deserialiser (SerDes) technology
• Low Voltage Differential Signalling (LVDS)
• Current Mode Logic (CML)
• PCI Express

Module 12 - PCB materials for high-speed design

• Material requirements for high-speed PCBs
• Transmission line attenuation due to dielectric and conductor loss
• Interconnect bandwidth limitation due to line loss
• PCB materials for lower loss
• Embedded capacitors and resistors

Module 13 - EMC Control

• EMC concerns
• Why EMC has become a major issue
• Definitions
• EMI mechanism, coupling paths and methods
• The five factors in EMI analysis
• What we can control in digital systems
• EMC guidelines
• Regulatory requirements

Module 14 - Principles of EMI generation

• Electromagnetic wave propagation
• Near field and far field
• Radiation generation
• RF fields generated on a PCB
• Differential mode and common mode currents and radiation

Module 15 – PCB structure

• Power and ground planes - layer stacking effects
• 20H rule
• Image planes
• Reducing common mode current loops
• Electrical lengths
• Split planes
• Isolation and bridging techniques

Module 16 – EMC from components to systems

• IC package parasitics
• EMI from large heatsinks
• Localised ground planes
• Impact of IC technology drivers on EMC control at component level
• I/O connections to/from PCB modules
• Backplanes and plug-in boards
• ESD protection
• Designing PCBs for EMC