High Frequency Measurements, Noise, and Troubleshooting in Electronic Circuits
Description
This seminar, and its demonstrations, are the product of a lifetime of experimentation and electronic design, 55+ years of electrical engineering (starting at age 12). Major concepts discussed in the seminar are illustrated with experiments on live circuits that were developed over years and are quite unique, enabling a deeper understanding of engineering concepts than seminars usually do. Many new topics and experiments have been added over the last few months that engineers and technicians will find very useful in producing, testing, or debugging new and existing designs of ALL types. No other seminar illustrates principles of design with experiments like this seminar does! Using the techniques presented in this seminar, design problems can be found and fixed in a few days, not weeks or months that are typical in the industry, not to mention being able to avoid the problems in the first place.
Course Outline:
Day One - Measurements
Scope Probe Measurements
- Introduction and background including live demonstration
- Kirchoff and Faraday voltage measurements
- Noise sources and effects
- Experiment that lowers confidence in measured results
- Useful tools for measurements and troubleshooting
- Technical background
- Null experiments to validate measured results
- Skin effect
- Inductance and mutual inductance
- Capacitive and inductive coupling
- Shielded cable operation using a graphical intuitive method (little math needed)
- Practical experiment on shielded cables
- Scope probe characteristics
- 10X “high” impedance passive probes
- “Low” impedance passive probes
- Active probes – single ended and differential
- Balance coaxial probe (500 MHz)
- Passive differential probe (2 GHz)
- Easy to build DC to 1 GHz probe
- The probe ground lead – resonance and input impedance
- 10X high impedance effects
- Low impedance passive probe effects
- Active probe effects
- Doubling the accurate bandwidth of most any probe with a capacitive input impedance
- Probe resonance experiment – live demonstration
- Active probe simulations – live demonstration
- Measured data on 4 GHz active probe
- Induced voltages in measurements – a source of error
- Error induced by ground currents into unbalanced measurements
- Ways to minimize the error
- Live demonstration
- Differential Measurements
- Types of differential measurements and probes
- Why most active probes did not work until a few years ago (2X error in peak reading)
- Lab data on a popular active differential probe showing the large error and high circuit loading
- 7 GHz and higher new generation active differential probes
- Balanced coaxial probe in detail (500 MHz)
- Passive differential probe in detail (2 GHz)
- Lab data and live demonstration
- Overview of Active Probe Design Philosophy
- Two approaches
- Using the wrong one will lead to significant error, and the choice is not obvious
- Why one brand of probe looks better its data sheet than the competition
- Shielded and unshielded magnetic loops
- How to interpret the loop output and relate to circuit noise, crosstalk, and general operation.
- Magnetic loop equivalent circuit and operation – graphical/intuitive approach
- Why shielded magnetic loops operate differently than engineers think and the implications
- Types of current probes and operation
- Equivalent circuit of a current probe
- Modifying the probe frequency response
- Null experiments to check probe operation and accuracy
- Limitations
- Circuit loading through capacitance
- Core saturation
- Modifying probe response experiment, live demonstration
- A surprising experiment involving skin effect, shielded cables, and ground loops, live demonstration
- Brief history
- Examples with data at <10 MHz, tens of MHz, and hundreds of MHz including CW sources and ESD
- How grounding at high frequencies is very different than at AC mains frequencies
Non-Contact Measurements – magnetic coupling
Current Measurements
Coupling Between Circuits and Equipment (Ground Loops Past, Present, and Future)
Day Two – EMC and Design Troubleshooting
Integrated Circuit Noise Measurement
- How to measure noise, crosstalk, and ground bounce inside the package with no direct connection
- How to gauge the impact of noise, crosstalk, and ground bounce in the package on IC operation
- Identifying signal integrity problems including those that occur with very low probability
- Identifying EMC problems
- Measuring internal risetimes in the chip itself
- Useful for both design engineers on the lab bench and EMC personnel
- Brief background and theory
- Relating common mode current to FCC/CISPR limits
- Troubleshooting EMC issues in the development lab
- Setting up the spectrum analyzer to measure common mode currents and spot problems.
- Experiments and demos
- Pigtail and system cable experiment in the time domain, live demonstration
- Pigtail and system cable data in the frequency domain, sometimes live demonstration
- Effects of board layout, ground plane splits in the time domain, live demonstration
- Effects of board layout, ground plane splits data in the frequency domain, sometimes live demonstration
- Emissions data from a PCB, paths that change layers
- Board layer stack-up effects
- IC coupling to nearby conductors, data and video
- Inductive and capacitive coupling
- How to measure structural resonance
- Needed equipment
- Several examples with data
- Kinds of operational and EMC problems that can be found
- Sometimes as live experiments
- What does “grounding” mean in an EMC sense?
- Examples of field problems (devices destroyed by signals in the environment)
- Why you can’t just use a cellphone to test for problems.
- A simple test for the development lab
- Effect of RF on opamps
- Grounding and loop size is very important even for 1 MHz gain-bandwidth product devices
- Why GHz layout techniques may be needed even for 1 MHz gain-bandwidth product devices
- Mitigation via added components
- Mitigation via selecting suppliers of opamps
- How test lab errors can cost you in a big way
- Radiated Emissions
- Conducted Emissions
- Radiated Immunity
- Conducted Immunity
- Check list
- Test equipment to bring with you to the EMC lab
EMC Troubleshooting
EMC Experiments
Resonant Frequency of Physical Structures
Cellphone Induced Problems
Analog Design - RF and EMC issues
EMC Lab Test Errors – “Trust but Verify”
Day 3 – ESD/EMI at the System Level
System Level ESD/EMI
- Introductory live demonstrations
- IEC 61000-4-2 System ESD Testing
- Description of the test
- Problems with the test
- Common errors that can fail a piece of equipment that should have passed
- Application (or misapplication) to IC devices
- Cable discharge – a problematic form of ESD
- Description of phenomena
- Experimental data
- A cable discharge test proposal (no current testing standard available)
- Unusual forms of ESD
- Why passing standard tests still leaves equipment vulnerable in the field
- di/dt and dv/dt effects
- Characteristics of ESD
- Unusual ESD sources not covered in any standard but that have caused field problems
- Characteristics of unusual forms of ESD
- Examples, experimental data, and live demonstrations
- Troubleshooting ESD problems
- Equipment and methods needed
- Experimental data
- Software considerations
- An impressive example
- I/O, memory, and processor issues
- Software simulation of an ESD event
- Methods to minimize risk from software
- Experiments (live demonstrations or by data depending on time and available equipment)
- Transient suppression plane (Where is “quiet” ground? Where you least expect it!)
- Using small inductors to improve ESD performance of equipment
- Parallel wire experiment in the time domain with ESD
- ESD effects in PCBs and cables
- Stressing circuits and systems – pulsed excitation
- Stressing individual ports of equipment
- Tools
- Methods
- Capacitive coupling
- Bulk injection probes and current probes
- Results
- Case histories
- Stressing PCBs and IC devices
- Tools
- Method
- Magnetic
- Characteristics of the injected pulse
- Results
- Case histories
- Video of the method in operation
- Live demonstrations on test and operating PCBs
- Stressing individual ports of equipment
- Stressing circuits and systems – CW excitation
- Tools
- Methods
- Similar to pulsed method but utilizing RF signal generators
- Results
- Case histories
- Locating impulsive events in 3D space
- Room level – mobile event locator
- Equipment level
- PCB level
- Sources of tools and equipment
Advanced Troubleshooting Techniques for Circuits and Systems
Instructor(s):
Douglas Smith, held an FCC First Class Radiotelephone license by age 16 and a General Class amateur radio license at age 12. He received a B.E.E.E. degree from Vanderbilt University in 1969 and an M.S.E.E. degree from the California Institute of Technology in 1970. In 1970, he joined AT&T Bell Laboratories as a Member of Technical Staff. He retired in 1996 as a Distinguished Member of Technical Staff. From February 1996 to April 2000 he was Manager of EMC Development and Test at Auspex Systems in Santa Clara, CA. Mr. Smith currently is an independent consultant specializing in high frequency measurements, circuit/system design and verification, switching power supply noise and specifications, EMC, and immunity to transient noise. He is a Senior Member of the IEEE and a former member of the IEEE EMC Society Board of Directors.
His technical interests include high frequency effects in electronic circuits, including topics such as Electromagnetic Compatibility (EMC), Electrostatic Discharge (ESD), Electrical Fast Transients (EFT), and other forms of pulsed electromagnetic interference. He also has been involved with FCC Part 68 testing and design, telephone system analog and digital design, IC design, and computer simulation of circuits. He has been granted over 15 patents, several on measurement apparatus.
Mr. Smith holds the title of University of Oxford Tutor in the Department of Continuing Education at Oxford University in the UK. He has lectured at Oxford University, The University of California Santa Barbara, The University of California Berkeley, Vanderbilt University, AT&T Bell Labs, and internationally at many public and private seminars on high frequency measurements, circuit design, ESD, and EMC. He is author of the book High Frequency Measurements and Noise in Electronic Circuits. His very popular website, http://emcesd.com (www.dsmith.org), draws many thousands of visitors each month to see over 250 technical articles as well as other features.
He provides training and consulting services in general design, EMC, and transient immunity (such as ESD and EFT), and switching power supply noise. His specialty is solving difficult problems quickly, usually within a couple of days. His work has included digital and analog circuits in everything from large diesel powered machinery to space craft to IC chip level circuits. His large client base includes many well known large electronic and industrial companies as well as medium sized companies and start-up companies.