Signal integrity problem learning method

As chip integration becomes higher and higher, production processes improve and cost pressures increase, chip manufacturers are making chips shorter and shorter when they are producing chips. This causes the rise and fall times of the signal to be very low even at very low frequencies. In the board design, if the design is unreasonable, the signal overshoot and oscillation are severe. So, as Eric Bogatin said: There are two kinds of engineers, one that has encountered signal integrity problems and the other that is about to encounter signal integrity problems. Therefore, analysis of signal integrity is particularly important.

Here, it is mainly about learning methods, sequences, simulation software, test and measurement, power integrity, and electromagnetic compatibility.

First, the method of learning

At the beginning, you can take a look at the simulation booklet in the ZTE EDA Tool Manual and follow the steps step by step. In this way, you can be familiar with basic processes and operations, and have a certain degree of understanding of the use of software. In the process of learning simulation software, combined with the first part of the book "High-speed PCB basic theory and memory simulation technology", the EMI part can be ignored first (when the theoretical understanding is more in-depth, look back) . This process is mainly to understand when to perform signal integrity analysis, when, can not be used; understand what is the transmission line, what is the reflection crosstalk, what is the timing analysis.

After that, you can go to the forum to learn about the current direction of signal integrity and the understanding of others. More importantly, in the future study and practice, if you encounter problems, you can go up and ask, as long as you have tried hard to think, someone will be happy to answer.

In addition, there will be a lot of Design rules on the Internet. Don't blindly believe that many rules have their limitations.

Here are the following forums:



SI high speed design China PCB.

Here are also the following books:

Signal Integrity Analysis Bergin, Li Yushan, etc., Electronic Industry Press;

High-speed digital design Johnson Graham, Shen Li, et al.

The above two books are highly recommended, and the signal integrity is almost one.

On this basis, you can look at the book "High-speed circuit design and simulation analysis." Of course, when you look at the book, you have to have a certain foundation.

Second, the order of learning

The reflection simulation of signal integrity can be performed first, followed by the crosstalk simulation, and then the timing analysis is performed;

After that, look at the relevant information on power integrity and simulate it.

Finally, you can consider the relevant knowledge of EMI.

Third, about the simulation software

Simulation software is just a tool. As long as your theory is mastered, each simulation software is similar. Moreover, as long as you master a common simulation software, it is easier to use another simulation software.

In the early stage, you can use the PCB SI simulation software. For signals below GHZ, the accuracy is still very high, and most of the simulation can be performed.

Later, when it comes to higher speed, backplane connectors, you can choose to use HSPICE. It's just that HSPICE needs to write netlists and scripts by itself, which is very time consuming.

In short, what is important to simulation is not the simulation software tool itself, but the designer's mind. Let the software do what it can do without going beyond the scope of the software.

Fourth, about test and measurement

For high-speed signals, test measurements are very particular.

We measure the vast majority of the instrument used in the oscilloscope. Regarding the use of the oscilloscope and how to measure it, here is a review of Mr. Wang Jinjin's blog.

V. About power integrity

Power integrity can be simulated by the PCB PI simulation software.

However, for this reason, there is no software that is particularly accurate for power integrity simulation, and only one trend can be seen.

The purpose of power integrity simulation is to determine the type and quantity of capacitors that need to be added. If there is no simulation, when the type is not matched properly, or the quantity is not enough, the power rail collapses easily. Therefore, in the actual design, more capacitors are often added.

Power integrity simulation, if it is to be done, must have a wealth of experience and a profound theoretical foundation. Even if I have done five years of related projects, I dare not say that I am proficient in this field.

Fortunately, from the practicality of simulation, power integrity simulation is not so important.

Sixth, about EMC

In front, there is no mention of EMI issues. In fact, EMC is largely related to signal integrity and power integrity.

Even in the book Signal Integrity Analysis, the entire system's electromagnetic interference and radiation is part of the noise source for signal integrity.

For example, in some cases, the EMC of a product does not pass the 3C standard. At this time, if it is determined that there is an inductance near the radiation source, the inductor is replaced by a magnetic bead, and it may pass. The reason is that the inductor is simply a reflection of energy, and the magnetic beads can absorb energy. There are also common mode currents for differential signals, and in many cases, an important source of radiation.

At the end of the day, you can truly achieve the same goal.

People have two ways to go, one must go, one is to go, you must take the road you must walk beautiful, you can walk the way you want to go~~~