An Interview with Eric Bogatin - Tilded Thumb Tenets

Welcome, Eric Bogatin!

• Eric is the Dean of Signal Integrity (SI) Academy, now part of Teledyne Lecroy
• He has also been teaching engineering for many years, including at Colorado University.
• Learning SI "on the streets" can't replace central (essential) principles like understanding and applying Maxwell's equations.
• The website that started it all is called, "Be The Signal", thought up by Eric's wife.
• Three tools in the toolbox
  • Rules of thumb
  • Approximations (formulas)
  • Numerical simulation tools
• Eric posted over 25 "Rules of thumb" articles on EDN.
• One example (and the first posted) was how bandwidth is (.35/rise time).
• Dave talked about similar principles in his video about oscilloscope bandwidth: https://www.youtube.com/watch?v=F-ZDiGmLvTs
• "Sometimes an OK answer now is better than a good answer late"
• One reason Teledyne bought LeCroy is because of the matching of the need (and solution to) Indium Phosphide technology. This was in the 100 GHz real time scope that Shahriar reviewed/tore down: https://www.youtube.com/watch?v=U3w_EWgGQuk
• A good general 2D field solver is Polar Instruments, though Eric was careful to point out that there is a wide variety of capabilities and price points for these pieces of software.
• The continued shrinking of circuit boards means that gridded (crosshatch) planes are in the market, especially for flex/consumer products. This helps with Signal Integrity.
• Instantaneous impedance is what the signal "sees" at each step. Characteristic impedance is expanding the instantaneous impedance to the entire line.
• Grace Hopper was one of the first programmers and was an admiral in the US Navy. She was a big fan of the ENIAC and tried to integrate them into programs. She carried a piece of string to help illustrate the distance a signal travels in air in a short amount of time.
• Signals travel roughly 15 cm per 1 nanosecond in FR4.
• Another rule of thumb involves ratios: get a 50 ohm line with a 10 mil width to 5 mil to dielectric ratio. It's the aspect ratio that's important.
• Layer stackup is often left to fab, which can be dangerous. Doubly so if you're depending on stack up because your power and ground planes are in the inner layers of your board.
• Yet another rule of thumb is to keep spacing twice the line width to reduce crosstalk.
• Making board bigger to guarantee it works is "buying insurance"
• 10MHz and above range is where you need the intuition. A handful of design rules will get you to 100 MHz. Beyond that, you need to pay attention and begin considering simulation.
• Eric will soon be writing Nuts and Volts articles about Arduino.
• SI academy was took the in-person classes and put them (mostly) online. They are now offered to individuals and corporations on subscription basis.
• The CU classes are also available on the site, as are some other example classes.
• It is interesting seeing where MOOCs are going, especially since very few are charging for courses.
• Chris doesn't like how testing / exams are handled right now. The SI academy doesn't have testing.
• Classes on the resume get you through the door, even if they are MOOCs. The interest level is what interviewers are looking for.
• Eric has written a large variety of books
  • Signal Integrity Characterization Techniques (free online)
  • Signal and Power Integrity Simplified (Prentice Hall)
  • Out of print books:
    • High Performance Packaging
    • Roadmaps of Packaging Technology