Book Recommendation -- By Eric Bogatin

Interconnects are no longer transparent, and if you don’t engineer signal integrity problems out of your design at the beginning, your product may not work. This is the warning Fadi Deek, corporate application engineer with Mentor Graphics, starts with in his new eBook titled Signal Integrity by Example.

In each of the four sections, he starts with a few of the essential principles, then poses examples that demonstrate these principles. I like the approach. Unlike other books that take a general approach to signal integrity, this book takes a few deep dives to apply the simple principles to explain relatively complex effects.

Deek offers a simple method to reverse engineer the output impedance of any driver—measure its open circuit voltage and find the load resistance when the output voltage drops by half.

Even the simplest circuits with real driver models can yield complicated-looking ringing waveforms. This eBook looks under the hood and identifies two often neglected sources of reflections: the package model and the input gate capacitance of the receiver. By considering these two features, many of the mysterious ringing effects can be instantly understood.

This eBook is the first in a series from Mentor Graphics. It covers four topics: transmission lines and impedance, reflections and terminations, crosstalk in microstrip and striplines, and differential pairs and signals. The next eBook in this series will cover PDN design.

While the essential principles provide a strong foundation to apply your engineering judgment, this book leverages many simulations as virtual prototypes in which to explore the details of design space. However, Deek cautions that whenever you do a simulation, you should always practice safe simulation by first anticipating what you expect to see. If you don’t see what you expect, investigate the reason.

For example, engineering judgment and many application notes suggest that tightly coupled differential pairs should have less channel-to-channel crosstalk than loosely coupled differential pairs.

In a simple simulation of the crosstalk between two differential pairs, Deek demonstrates that, in some cases, this expectation does not match the real world. He shows that when differential impedance and line width are kept fixed and the coupling in a pair changes, two loosely coupled pairs have less crosstalk than two tightly coupled pairs with the same channel spacing.

By looking at the fringe fields, Deek is able to show the root cause of this behavior and recalibrate how we think about and solve signal integrity problems.

If you care about signal integrity, you are sure to pick up a few nuggets of insight from this new eBook.