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Design007-Sept2018

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30 DESIGN007 MAGAZINE I SEPTEMBER 2018 10 Fundamental Rules of High-Speed PCB Design, Part 1 Beyond Design by Barry Olney, IN-CIRCUIT DESIGN PTY LTD / AUSTRALIA Over the years, I have focused on high- speed design, signal and power integrity, and EMC design techniques in a plethora of pub- lished technical articles—all of which have key points to consider and present a tremen- dous amount of information to absorb. In my next few columns, I will elaborate on ten of the most important considerations to embrace to achieve successful high-speed PCB designs that perform reliably to expectations. Figure 1 lists the 10 fundamental rules of high-speed PCB design that I deem the most important to follow, although they may change after months of deliberation, like what hap- pened with the laws of thermodynamics. The first established thermodynamic principle, which eventually became the second law, was formulated by Sadi Carnot in 1824. By the late 1800s, three laws of thermodynamics were clearly defined. However, in the 1930s—long after these three laws were already widely accepted—Sir Ralph Fowler and E.A. Guggen- heim felt that another law, which they saw as the foundation of earlier laws, should be incor- porated. Hence, it was numbered the zeroth law. Thus, there is always room for one more at the top! The 10 fundamental rules of high-speed PCB design are: I. Establish Design Constraints Always create a strategy for high-speed design requirements and set constraints based on pre-layout analyses or recommendations and guidelines prior to commencing the design. II. Control the Impedance Match the transmission line impedance to the driver and load. Create the stackup and define terminations to match the impedance. III. Floor Plan the Placement Based on Connectivity Place components by functionality and ana- log and digital groups to minimize interac- tion between different logic families and improve routability and timing. IV. Define the Power Delivery Planes and Paths Define the power/ground regions and plane layers. Partition (not split) the ground planes. V. Optimize the Power Distribution Networks (PDNs) Create a low AC impedance deliv- ery path by optimizing the bypass and decoupling capacitors and mounting induc- tance and plane resonance from DC to the Figure 1: The 10 fundamental rules of high-speed PCB design.

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