Believe it or not, this is my 100th “Beyond Design” column. The editors at I-Connect007 are a great group to work with. I eagerly await each month’s magazine release to see how creative the team have been with editing, laying out, and producing my column.
I-Connect007 was founded in 1999 and is now the industry’s longest-running electronics media portal. Personal development and continued education are so important—especially in a relatively new and ever-changing industry where designers are continually pushing the envelope. And with its line-up of three online magazines—Design007 (featuring Flex007), PCB007, and SMT007—I-Connect007 provides the latest information from industry experts.
My first “Beyond Design” column on ground pours was published online in 2011. Over the years, I think that I only missed publishing one month when I was on vacation. I’ll have to work on that lazy streak! When I was first approached to write a regular column, I thought that I might be able to convert my course on advanced design for SMT, which I had been presenting throughout Australia and New Zealand since 1994, into a number of segments. However, I never envisaged reaching the 100 mark.
“Beyond Design” focuses on high-speed PCB design, signal and power integrity, and EMC design techniques. To wrap up my 100th column, I look back over the past 99 columns and reflect on what I believe to be the Top 10 most enlightening for high-speed PCB designers, counting down in reverse order of preference.
10. The Dumping Ground
Ground planes in a multilayer PCB allow the designer to ground anything, anywhere, without having to run multiple tracks, the net needing grounding being routed directly to the ground plane on another layer. However, this is a simplistic approach. One should also consider the presence and interaction of the power distribution network (PDN) and how and where the return current flows. A logic schematic diagram masks details crucial to the operation of unintentional signal pathways vital to your understanding of signal performance, crosstalk, and electromagnetic emissions.
When you plan your stackup, be aware of which plane(s)—either power or ground)—will be the return path for your critical signals, and ensure there is an unobstructed return path. The best way to think of this is to imagine routing a return trace adjacent to each signal trace on the reference plane. Where will the current flow, and is it unobstructed? The reference plane adjacent to each signal layer allows the return current to flow as closely as possible to the signal trace reducing inductance and loop area.
To read this entire column, which appeared in the September 2019 issue of Design007 Magazine, click here.