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66 DESIGN007 MAGAZINE I AUGUST 2021 PCBs don't explode every day, but if your design calls for more than one voltage on a power plane layer, spontaneous combustion is just one of the many problems this tricky chal- lenge for PCB designers can cause. It may seem counterintuitive, but when a PCB fails spectacularly, the cost is less because it's both immediate and easier to measure. If you make a small crater the first time you turn on the first production device, you lose an entire lot of boards and the time spent on designing and prototyping. When less notice- able or intermittent issues occur, they can eventually cost far more depending on how long they remain undiscovered. e severity of the PCB failure seems to have an inverse relationship to the amount of effort The Split Planes Challenge required to fix it. When there's smoke coming out of your PCB, it's relatively easy to find out why. Digital glitches and signal anomalies are more subtle issues that can take many hours of tedious detective work to solve. Split planes are enclosed regions on an inter- nal plane layer, and problems with them can be among the most difficult design flaws to ferret out. e further a board makes it through the development cycle without someone notic- ing, the more it costs. Production delays and resources directed at solving the problem can be quite costly, but the worst-case scenario involves malfunctioning boards making it out into the field. ose events create warranty claims, prod- uct recalls, damaged reputations, and lost jobs. Here we will explain why managing split planes can be so challenging and examine some best practices for avoiding this common issue. Why Does This Happen? ere oen exists a gap between what a design tool allows the designer to do with split planes and how difficult it can be to rec- ognize issues with the design. Your PCB design tool will offer the ability to assign voltage amounts to the entire plane, but that can lead to problems if your design assigns multiple voltages to the same plane. Problems are avoided Connect the Dots by Matt Stevenson, SUNSTONE CIRCUITS

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