Many people have been asking for the book Signal Integrity for PCB Designers by Vikas Shukla. The book was in great demand in world wide, especially in China and Hong Kong and some what in India.
Looking into the demand, the book has been made publicly available and and can be accessed at Signal Integrity for PCB Designers . This should help anyone who can not purchase the book.
At the time of writing the first two chapter has been uploaded and the process of making complete book available is being done. Please stay tuned as more upload is being done.
The book is available at amazon and can be purchased. It has been competitively priced at $55. Older books are available for as low as $25.
Reference Designer also has some useful programming tutorials. One of the most sought after tutorial is C Sharp Tutorial . If you have any interest in learning C sharp, you will find it extremely useful.
Signal Integrity
Signal Integrity
This question is asked often by the PCB Designers. I thought to put it up in this blog. A differential
bus like LVDS contains a structure similar to the one shown below
|>—————–||—————-|>
|>—————–||—————-|>
There is Driver and then a pair of ac series capacitors placed on the positive and the negative rails of the differential bus, then a differential PCB trace again and then LVDS receiver. Let us assume that the receiver has internal termination .
The question is – What is the optimum place to put coupling cap when the LVDS bus is ac-coupled.
Should it be close to driver or should it be close to the receiver or right at the center.
The capacitor acts as AC coupling and assuming that the capacitor itself has no parasitics, it does not matter where we place the capacitor. This rule give freedom to the PCB designers and eases the layout constraints. If you want a next degree of accuracy, you should note that the pads and the traces joining the capacitor may cause reflections. If you keep the capacitors symmetrical, even these reflections will be symmetrical and should not cause any issue. Placing the capacitors symmetrically is key to the better signal performance rather than the closeness to either the driver or the receiver.
Why is Capacitor used
HyperTransport another differential bus does not use capacitor. Many other differential signaling schemes do not use capacitor. Why is the capacitor used in PCI Express differential signaling.
The purpose of the capacitor is to detect the presence of the receiver. During the initialization, the common mode voltage on the transmitter charges the capacitor. The presence of the absence of the receiver is detected using this charging time constant. This allows transmitter to shut down if no receiver is absent.
This gives out one simple rule. If the transmitter and the receiver are on the same PCB, it does not matter where you place the capacitor. If however, the receives is on a separable PCB, the capacitor should be placed in the side near to the transmitter. This allows the detection of the plug in card.
Signal Integrity
si, Signal Integrity
Many PCB Designers and engineers often have the question about Analog and Ground Separation. A noise sensitive analog circuit can be affected by the noise generated by returning digital signal. How it is possible to separate the digital and analog grounds so that the noise on the ground signal does not effect the analog circuit.
How Noise from Digital Ground Enters Analog Circuit
The current returning in the digital circuit creates noise. If there is an analog circuit in the path of the returning ground signal, this noise enters the Analog circuit. This leads to two basic facts that you need to keep in mind.
1. Analyze and imagine all areas of the digital signal return path.
2. The noise generated in the ground will be severe if the rate of the change of the current in the return signal in higher.
Is Separate Analog and Ground always necessary
Analog and Ground separation is not always required. You will have to visualise the return current path of all the digital signal to be able to take a decision, if the separate analog and ground planes or their separation is needed.
More about it coming soon…..
Signal Integrity
si, Signal Integrity
I have seen a high demand for the online quizzes. Early in my college life, I was impressed by the books that had a lot number of solved examples followed by a large number of unsolved questions. One of the reasons for this was I grew up in a very competitive atmoshphere. There was no option but to excel and be in the top 1%.
When I wrote my book Signal Integrity for PCB Designers I has this aspect in mind. I included as many questions at the end of chapters as possible. These questions, in the form of multiple choice answers form the basis of testing your skill.
Recently, I came across skill-guru an online platform where a “guru” can post the questions alongwith answers and explanations. The students can take the test online at any time. The questions in my book could reach to a greater audience. Since I had published the book myself, I could post the questions without requiring permission from the Publisher.
If you want to test your signal integrity quiz for fun or for refreshing your Signal Integrity basics you may like to take the following two quizzes.
Signal Integrity Quiz #1
Signal Integrity Quiz #2
How skill-guru works
Skill-Guru is collaborative platform which allows the subject area experts to create tests. When some one takes a test designed by guru, he can assess the level of his knowledge and, can therefore improve upon his skill. This helps students.
If you have an expertise in your area you may like to become a guru and post questions in skill guru. If you want to test any skill in your area of study you may like to see if there is any quiz available in the are of your expertise at skill guru.
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The book “Signal Integrity for PCB Designers”, has been cited in the article – “PCB Stackup analysis and design”, by Riazi, Abe Abbas.
In the part 5 of the article, the author discusses the PCB Stack up. The complete article can be found at
PCB stackup influences board impedance, signal integrity and the EMI performance of the system
Some more Signal Integrity topics
Signal Integrity – Tips for EMI Reductions
Signal Integrity – Tips for Power Supply Noise Reduction
Tips for Integrity of Point to Point Signal
Signal Integrity
si, Signal Integrity
Signal Integrity for PCB Designers by Vikas Shukla
I received the book this past weekend. I browsed through the material,
and have read the preface and started chapter one. I'm looking forward
to reading the entire book and applying the techniques as well. I
think this book will make a great addition to my PCB library.
Thanks,
Richard
richard.upton@ngc.com
Signal Integrity
si, Signal Integrity