Signal Integrity

Here’s my top ten reasons NOT to care about signal integrity. What’s the lamest excuse you can think of? Add it in the comment box!

10. Hey! My chip meets spec. It’s the OEM’s job to design it in right.

9. The speed of light is 670,616,629.4 miles per hour. That’s really, really fast.

8. I never had that problem on my last project, and this revision is only 30% faster.

7. The via stubs don’t connect to anything. What harm can they do?

6. My PCB vendor specs convince me I won’t have a problem: “Loss tangent – pretty close to zero. Roughness – almost no roughness. Metal resistivity – are you kidding? Copper’s a real good conductor.”

5. Skin effect? Isn’t that something to do with Photoshop?

4. S-parameters? No thanks. Don’t you have an RGLC SPICE model?

3. 10 picoseconds? Listen to me: 10 picoseconds to ten decimal places is 0.0000000000 seconds.

2. If it doesn’t work we can always step up to Rogers’ material.

And the number 1 reason NOT to care about signal integrity is:

1. We’re hoping lower speed products will make a come back!

TGIF. Have a good weekend!

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Here are my thumbnail reviews of some signal integrity textbooks. They reflect my personal views, not those of Agilent. You can add your thoughts in the box below.

• Timing Analysis and Simulation for Signal Integrity Engineers by Greg Edlund
  This book takes a different approach to signal integrity then the "traditional" Bogatin and Johnson & Graham approach (see below) in that the starting point is not the interconnect, but that diminutive prima donna of signal integrity, the flip-flop in the receiving chip. In my mind’s eye I imagine this scene: "If I don’t see a clean zero or one during my set up and hold periods," lectures the flip-flop, one hand on hip, the other wagging a threatening finger, "I’m going to go metastable." And so the game begins. How to deliver on that demand? Greg’s twenty years – and counting – experience as a hands-on signal integrity engineer makes his textbook authoritative and his narrative style makes the book accessible.
• A Signal Integrity Engineer’s Companion Real-Time Test and Measurement and Design Simulation (Geoff Lawday, David Ireland, and Greg Edlund)
  Some of the chapters (2, 4, 9) in this books are the same (give or take a revision or two) as ones in the book above, so this book should be considered if the non-overlapping material is of value to you. Not sure why the publisher "double-dips" in this way.
• Signal Integrity – Simplified (2ed due for release July 27, 2009) by Eric Bogatin
  It was Eric who coined the phrases "There are two kinds of engineers — those who have signal integrity problems, and those who will." and (with respect to all signal integrity issues) "It depends."
  I haven’t seen the second edition yet, but the first edition has the "traditional" signal integrity focus on the properties of the interconnect, the impairments that it inflicts on the poor signal, and how to design around them within the limits imposed by physical laws. Eric also has a new book coming out in September – Signal Integrity Characterization Techniques – co-authored with my colleague Mike Resso. I’ll review it when I can.
• High Speed Digital Design: A Handbook of Black Magic and High Speed Signal Propagation: Advanced Black Magic by Howard Johnson and Martin Graham
  Published in 1993 and 2003 respectively, one frustration with these two very popular books is that I can never quite decided whether the latter is volume two of the former, or whether it’s the second edition. There’s certainly a lot of overlap between the two, but the second isn’t a true superset of the first. It smacks of another case of Prentice Hall "double-dipping." Both volumes/editions have a "traditional" focus on the PRBS signal in the frequency- and time-domains, and its interaction with the interconnect. Personally, I prefer the flow of Eric’s book for "cover-to-cover" reading, but there’s a lot of good reference material and anecdotes here that I dip into when needed.

Other texts that are on my ever expanding to do list. I’ll try to add reviews here someday? Or you can add your thoughts in the box below.

• The SPICE Book by Andrei Vladimirescu
• Jitter, Noise, and Signal Integrity at High-Speed by Mike Peng Li
• Learn Signal Integrity Design Principles With Mathcad: Interactive textbook/CD for EMC/EMI/PI/SI by David Norte
• Semiconductor Modeling For Simulating Signal, Power, and Electromagnetic Integrity by Roy G. Leventhal and Lynne Green
• Power Integrity Modeling and Design for Semiconductors and Systems by Madhavan Swaminathan and A. Ege Engin
• High-Speed Digital System Design: A Handbook of Interconnect Theory and Design Practices by Stephen H. Hall, Garrett W. Hall, and James A. McCall
• Advanced Signal Integrity for High-Speed Digital Designs by Stephen H. Hall and Howard L. Heck

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The Agilent ADS User Group Meetings in Rome (13 May) and Böblingen (14-15 May) had three signal integrity papers. The authors have kindly given permission to post them here.

• Francesco de Paulis and Antonio Orlandi, UAq EMC Laboratory, University of L’Aquila, Italy:
  Using Equivalent Circuits for the Analysis of Complex Power and Signal Integrity Problems
  .
  They compare fast circuit simulation with ADS to complex and time consuming 3D models and conclude that ADS is not only a tool for designing. Its flexibility allows its use as tool to investigate the fundamental mechanisms of relevant power and signal integrity issues and that it is a critical tool for engineering.
• Karsten Drögemüller, ix-cad:
  High Speed Digital Signal Path Design for a 40 Gb/s Optical Receiver
  .
  Karsten shows how ix-cad achieved first pass success in designing the 40 Gb/s digital signal path for an optical receiver using ADS.
• Hermann Ruckerbauer, EyeKnowHow Signal Integrity Consulting:
  Signal Integrity Optimization of a Complex Memory Bus System
  .
  Hermann shows how to explore the system design space by applying the ADS optimizer to various pulse response goals.

Hermann also posted on YouTube this entertaining and informative video on the eye pattern a.k.a. eye diagram:

Thanks to everyone who participated!

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