Signal Integrity Pcb Designers
The Printed Circuit Designer's Guide to.™Signal Integrity by Example by: Fadi Deek, Mentor, A Siemens BusinessSignal integrity issues remain a concern for many in the electronics industry. This micro eBook details the importance of eliminating signal integrity challenges.
Written by signal integrity engineer Fadi Deek of Mentor, A Siemens Business, the chapters explore four possible signal integrity problems using an understanding of essential signal integrity principles.Deek explores how to reach effective design solutions and make strong engineering tradeoffs through analysis techniques, best design principles, and software tools to achieve accurate simulations and measurements. This eBook has something to offer for any engineer interested in identifying problems, root causes, and solutions surrounding electronic transmissions.ISBN: 978-0-9982885-2-9. Fadi DeekIn 2005, Fadi received his B.S. Degree in computer and communications from the American University of Science and Technology (AUST) in Beirut, Lebanon. That same year, he joined Fidus Systems as a design engineer. He designed circuit boards at Fidus for three years.
Signal Integrity Basics
In 2010, he received his M.S. In electrical engineering from the University of Arkansas in Fayetteville. He then joined Mentor, A Siemens Business, as a corporate marketing engineer.
In 2013, Deek became a corporate application engineer supporting the HyperLynx tool suite. In parallel, he is also pursuing his Ph.D. At the University of Colorado in Boulder under the supervision of Dr. Eric Bogatin.
Mentor, A Siemens Business, is a world leader in electronic hardware and software design solutions providing products, consulting services, and award-winning support for the world’s most successful electronic, semiconductor, and systems companies. We enable companies to develop better electronic products faster and more cost-effectively. Our innovative products and solutions help engineers conquer design challenges in the increasingly complex worlds of board and chip design.
Corporate headquarters are located at 8005 S.W. Boeckman Road, Wilsonville, Oregon.
Book Recommendation - By Eric BogatinInterconnects 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. Eric Bogatin is currently the dean of the Teledyne LeCroy Signal Integrity Academy.
Additionally, he is an adjunct professor at the University of Colorado – Boulder in the ECEE department, where he teaches a graduate class in signal integrity and is also the editor of the new journal Signal Integrity Journal. Bogatin received his BS in physics from MIT, and MS and PhD in physics from the University of Arizona in Tucson. He has held senior engineering and management positions at Bell Labs, Raychem, Sun Microsystems, Ansoft and Interconnect Devices.
Bogatin has written six technical books in the field, and presented classes and lectures on signal integrity worldwide. Happy Holden is the retired director of electronics and innovations for GENTEX Corporation. Formerly, he was the chief technical officer for the world’s largest PCB fabricator—Hon Hai Precision Industries (Foxconn).
Prior to Foxconn, Holden was the senior PCB technologist for Mentor Graphics and advanced technology manager at Nan Ya/Westwood Associates and Merix. He previously worked at Hewlett-Packard for over 28 years as director of PCB R&D and manufacturing engineering manager.
He has been involved in advanced PCB technologies for over 47 years.
The clarity of TV signal transmission these days is amazing. I can still remember the days when I had a set of rabbit ears perched atop my 19” RCA. It was a challenge to position them just right to get the clearest picture, not to mention having to adjust them for every channel. Sometimes it’d take all night just to find the channel I wanted, so I’d sit down for five minutes and then head to bed. And if the weather was bad, forget about it.While an occasional snow storm might make my TV signals a little choppy, that’s nothing compared to the old days. Network designers in the latest TV signal technologies such as high-speed cable, internet, and satellite have to consider transmission paths, obstructions, and interference when they’re planning and developing our modern TV needs.
But signal transmissions aren’t strictly for the network designers—you can have the same types of problems with your PCB design. Since you don’t have any rabbit ears to play around with on them, protecting against signal integrity issues is critical for keeping your PCBs running smooth and without static. HDMI, or Composite?
Know the Signal in Signal Integrity IssuesWhether it’s cable, satellite, Netflix, Hulu, Amazon, Youtube—smart TV, flat-screen, plasma—there are hordes of ways to receive the signals you need to watch the television you want to see. Similarly, most PCBs will include several signal types. Some of the most are:Power Supply Signals: Depending upon complexity, you may have several different levels of power supply Signals. For example, most processors require signals in the 3-5V range, while amplifiers may require bias voltages of up to 15V range.Data Signals: Data may be either analog or digital. For analog, typical ranges are +/- 10V. For digital, the range may be 0-5V or +/ 5V depending upon signal format.Control Signals: These are usually for switching devices on or off and are typically 0-5V signals.Communication Signals: These may have signal strengths as low as in the microvolt level. These are typically RF and the frequency may vary over a wide range.In addition to signal strength, in the case of analog signals, frequency is also an important consideration that must be incorporated into your PCB design.
This is especially important for PCBs that incorporate communication devices where the frequency levels can be very high. Output Dimensions and Routing Considerations: How Wide?For very simple PCB designs, you can usually get away with designing routes to accommodate the extremes of current and voltage. For example, using a single trace width throughout that can handle the maximum ampacity. Your board may work fine for these cases, although, this is far from the best practice. If you are like me, these are far and few between and we usually want to optimize our boards by making them as small and multi-functional as possible.For these more complex PCB designs, extreme care has to be taken and routing is not quite as simple.
Signal Integrity Design Rules
We want to design routes that match the signals they have to carry. Consult the following table for general considerations:Routing ConsiderationsPotential ProblemsRouting SolutionsTrace lengthSignal strength loss,MinimizeDistance between tracesInterferenceRoute perpendicularTrace anglesCrosstalk, radiationRound, Use 45° instead of 90°Via usageReflectionsMinimizeEmploying the above-suggested solutions reduces losses, space, and costs. However, to properly incorporate these requires using the. Make Sure to MuteNoise in older TV signal transmissions left you trying to view your favorite program through a layer of snow. Today, noisy transmissions either give you a disjointed puzzle or no signal at all. The can be from a number of sources.
For example, perturbations from switching IC pin states, interference from radiating devices such as oscillators into nearby traces, multiple frequency signals on the same trace, and other sources.It is virtually impossible to completely eliminate noise from most complex PCB designs. However, there are ways to minimize noise. Your best asset in eliminating noise is the placement of components. All component radiation is frequency dependent and the higher the frequency (signal change) the shorter the distance from the source. Therefore, you should place components that are processing the same signal away from other components. Place components where signals originate and terminate close to each other.You could also try implementing bypass capacitors.
Signal Integrity For Pcb Designers
These should be tied directly to the ground, if possible, and sized appropriately. Note that any inductance will combine with the capacitor to set up a filter circuit.Noisy digital TV signal Twist the Ears Together: Differential TransmissionsSignal integrity can be improved by using, whenever possible. Most IC designers try to implement this; however, at times differential pairs may be routed to pins that are not adjacent to each other. From a PCB design perspective, we want to do the following:.Route differential pairs together.Use the same trace width and length (as much as possible).Route on the same signal plane or layer.Ground Planes Can Make Signal Integrity Easycan provide a central layer reference for multiple circuits, which can significantly reduce your pin connection and trace numbers, not to mention simplifying the visual layout of a complex PCB.