Customer Reviews

High Speed Digital Design: A Handbook of Black Magic

5 star:		(16)
4 star:		(7)
3 star:		(2)
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1 star:		(1)

 

 

First, I'll critique the sub-title: a handbook of Black Magic. High-speed digital design is not black magic. It is the application of science. The sub-title does the book a disservice.

Second, I should caution young engineers that the authors of this book enumerate several stratagems in high-speed design; some good, some bad. That is, not all of the tricks in later sections are sound engineering practices. Experienced engineers will be able to differentiate between sound engineering practices and hacks, and when compromises should be made. Young engineers may be lead astray too easily.

Lastly, this book is a good book if you already know something of the subject. If you had only to buy one book, I'd recommend "High-Speed Digital System Design: A Handbook of Interconnect Theory and Design Practices" ISBN: 0471360902.

After reading that book, I'd purchase this book, as this book has some practical information, for example, on choosing capacitor dielectrics, oscillators, etc., not contained in the first.

This book is useful if you want to have a long series of equations available in one place to jog your memory. But if you want to learn something useful and practical- and real-world - then perhaps you would be better off doing a web search for application notes, tutorial papers, and articles, particularly from semiconductor manufacturers, and vendors of high-performance test equipment such as Agilent, Tektronix, and others.

To take one example (page 134,) Johnson purports to describe problems associated with a wire-wrapped prototype processor board containing TTL devices operating at high edge rates ( 2 ns.) According to Johnson, the design engineers failed to realize that the circuits would ring excessively, making the board unusable. To "prove" this he posits a model consisting of a 30 ohm TTL driver, with a 2 ns rise time, a 4" length of wire with 89 nH of self inductance, and a 15pf load - a series LRC circuit. Yes, this circuit will ring wildly, but the model is totally incorrect. The TTL input is not considered, which has a relatively low input impedance in the low state since it is current operated. This circuit -effectively a parallel LRC - does not ring nearly as much, as any experienced engineer knows. As a reality check, remember that wire wrap was successfully used for years by thousand of engineers. To listen to Johnson, though, this technology is almost unusable. Wire wrap circuits do ring, but under his example, the real amount of overshoot/undershoot is well within the limits of TTL. Further, no real circuit produces textbook looking traces, so the role of experience is to learn what worst-case design means, and what is acceptable for good manufacturing yield. Lesson: real experience teaches you how to produce correct, functional models. An incorrect model will cause you grief.

Much could have been done here, to be useful, by way of analysis and of recommendation. The wire should have been modeled as part of a transmission line, not as a lumped element, which any high speed digital design engineer would know, and the idea of terminating a transmission line should have been introduced. This is standard fare. Even with the series LRC, instead of deriving the formula for critical damping, he instead says: "This approximation (reduce Q to .5) is derived from the solution to a second order linear differential equation describing an RLC low pass filter. First find the point at which the derivative of the solution passes through zero (a maximum point) and then evaluate the solution at that point."

Got that? Take the derivative of a solution you want to find? Any book on circuits will reduce this to the solution of a quadratic equation. Obfuscating something that's really elementary does not help produce genuine insight. But this is what Johnson does throughout the book.

Isn't it simpler to say that if you have fast rise time signals, treat most connections as transmission lines, and add termination resistors? As for a series RLC, use the formula for critical damping: R = 1/2 (sqrt(L/C))

Being a hardware designer for DSP and CPU boards, this is the most interesting book I have read the last 10 years. I read the entire book nodding my head and saying "This all makes sense". All the theory is there, but what makes it readable is the autor's comments on what really matters; such as: "The inductance of vias is more important than their capacitance to digital designers"

Great book. BTW, the author lists a LOT of errata on his website, enough to take over an hour to mark up my copy (5th printing). Although it's nice he documents this so well, it's a pain in the rear, so you may want to verify the edition you're buying to avoid this extra effort. On page vi, above ISBN, look for reverse sequence; example: "10 9 8 7" indicates 7th printing (cryptic, I know). Most recent printing is 15th edition (least amount of errata). The book is loaded with equations and diagrams. It would be nice to see more derivations, but at least the equations are there in the text, and in the appendix. I thought a few other reviewers were a bit harsh. The book is not perfect, but nevertheless a great resource. His second book is impressive, but more advanced; this original title is my "workhorse" book. also, check out his website (sigcon.com) for lots of articles and resources.

This book will be a delight for digital designers who don't know much about signal integrity. It is very basic, doesn't use too much math or theory and covers a lot of fundamental useful concepts. There are original discussions that are not seen in many other books such as measurement techniques showing the effects of the ground clip of a probe on the measurement accuracy. Discussions on how to measure inductance and capacitance of traces are also very nice. There are easy to read sections on crosstalk. However, there are also quite a few sections that could have benefited from a more standard text book approach building the subject gradually.

The books biggest weakness is also perhaps its greatest strength: It doesn't go into more rigorous derivation or theoretical discussions. Although this makes the book easier to read in general, sometimes actually it makes it harder to understand what is going on! For example, right in the very first pages in Figure 1.1 the author shows the frequency spectrum of a random digital waveform. There is no explanation of where it came from. I can understand no mathematical derivation existing, but at least the author should try to explain what is going on. It is also unsatisfying how some of the discussions are so intuitive but there is no simulation or theoretical proof of them. For example the author states "Use extra ground planes, not power planes, to isolate routing layers." Although there is some discussion of why this is recommended as usual there is very little to "prove" it by an example.

If you want to learn about very advanced coverage of crosstalk and many other EMI/EMC ideas you should buy Clayton R. Paul's book "Introduction to Electromagnetic Compatibility." By the way that book has the most impressive coverage of how the spectrum of a digital waveform shown in figure 1.1 in "Black Magic" can be calculated.

Add Johnson and Graham to the list of people who can write large, highly technical books full of useful, pertinent information, and package it all in a way that's mostly very readable and which mixes just the right blend of rigorous academic structure with good old-fashioned "when all else fails, you might get away with this" hacks. This book is by no means a thorough, academic grounding in the subject matter, but it works well as an introduction for people who have some background in conventional electronics, yet little or no background in the specifics of high-speed digital design.

Considering how specialized and complex the book's subject matter is, it's surprising how well the authors manage to avoid hard math; they obviously made a conscious effort to use the most intuitive formulas possible whenever they could. There are maybe a handful of differential equations in the book, but most of the math requires no calculus, just basic algebra. The moderately math-phobic should be able to handle this book if you can understand what derivatives and integrals are.

A bit of a rant: Everybody gets so hung up on the title! Did any of the people who complain that HSDD isn't really "black magic" actually bother to even open the book? Right in the preface, the authors explain that HSDD is regarded as something of a "black magic" by engineers because it isn't taught in most college programs, but "The authors would like to dispel the popular myth that anything unusual or unexplained happens at high speeds. It's simply a matter of knowing which principles apply, and how." The title is meant to be humorous, people; lighten up! A lack of a sense of humor is a sign of an ineffective engineer.

This book really is just an introduction. You're not going to go out and design a gigahertz-level PC motherboard when you've read it through, but it'll prepare you for more advanced material like the "Advanced Black Magic" sequel, and tons of similar advanced books on the market. The book's strength is in its easy writing style and broad, concise scope. Recommended for anyone who knows basic electronics but wants to become a professional signal electronics engineer.

Johnson's High Speed Digital Design (1993) is widely cited as the definitive book on signal integrity for digital design. I've had it on my bookshelf now for about 4 years, but to be honest: I regret buying it.

The subject overview is definitely useful; however, as some have pointed out, the theoretical coverage isn't very good. Johnson presents a lot of equations, but without giving readers an intuitive understanding of what's really going on.

Also, IMO, Johnson isn't a good writer. He lacks depth and the ability to explain things clearly. To be honest, to learn signal integrity, there isn't really a good book out there.

I was first introduced to this book when I signed up for a class at University of California, Santa Cruz - Extension. The class was titled "High Speed PCB & System Design". There were people with varied levels of experience (beginner to veteran) in the class. Almost everyone thought that the topics that were covered in this book (which was the prescribed text book for the class) were just what was needed to fill the void in the learning process to become a successful design engineer.

Lot of the material covered in this book has been handed down by word of mouth for many years. This book covers many important aspects of board design - transmission lines, grounding, cross talk, reflections, termination & vias. In the high speed world if proper design principles are not applied, signals can behave in an unusual manner. Signal integrity is of utmost importance. None of these are dealt with such a practical approach in school, and hence this subject matter came to be known as "black magic" among practicing engineers.

This book covers analog & digital design principles in depth, and gives you real world examples. At the end of every section, the authors summarize the key points that were learnt from that discussion. It is a very useful feature. You can just refer to these if you have to find out what kind of termination your signal needs or how long you can run a clock line without signal interference. In addition to these essential topics, this book also covers other useful topics such as clock distribution, cables & connectors.

It is needless to say that this book in the right instructor's hands would be an explosive combination.

As a researcher in board-level programmable device design, i found it always be my "real bible" for solving lots of practical problems. This book not only gives you practical design considerations, but it does provides teoretical interpretations. I like the "points to remember". Thank You.

Very good balance of theory and practice, nice examples from the real world, must-read for anybody designing high speed digital logic and having PCB board design in mind.