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42 DESIGN007 MAGAZINE I JANUARY 2022 tance and to reduce the potential of generating noise. e connec- tions between these parts should be routed with wide traces on one layer only, avoiding the use of vias, except for the vias that extend into the ground plane to help with ther- mal dissipation. And it's also impor- tant to keep these power circuits isolated from sensitive digital and analog circuitry for the best signal and power integrity of the design. However, what designers are less familiar with is how to work with high-voltage circuitry, which is increasing in importance as more high-voltage design work is being done. High-voltage circuitry can be found in everything from comput- ers and consumer products to large industrial equipment, and designers must learn the intri- cacies required to lay them out. For instance, higher voltages can arc between exposed metal conductors on a circuit board if those leads, pads, traces, or other areas of metal are too close to each other. With the unexpected arcing of high-voltages also comes the break- ing down of the different insulating barriers in and on a circuit board. Eventually this contin- ued arcing can create an actual short between the exposed conductors, creating a potentially dangerous situation that can cause a lot of damage. Clearance and Creepage To eliminate the potential of arcing in high- voltage circuits on their boards, it is essen- tial for PCB designers to understand both clearance and creepage spacing rules in their design. While clearance is the direct space between two metal conductors from a line- of-sight perspective, creepage is the space between the two conductors that follows the physical contours of the circuit board. ese clearances must be adhered to for the board to avoid problems with its high-voltage circuitry. Even placing high-voltage components on opposite sides of the board may cause a prob- lem if the parts end up violating the allowed creepage spacing distance. ere are many other aspects of high-volt- age circuits that PCB designers also need to understand in order to successfully lay out these boards. For instance, which board mate- rials are better for applications of high-voltage, what copper weight should be used, and how can that copper be distributed throughout the board to ensure its manufacturability? Fortu- nately, this edition of Design007 Magazine is focused on high-voltage design, and there are numerous experts weighing in here that can offer some help. But, Did We Crash? Now, back to my crippled B-17 flight. If you've ever watched the movie "Memphis Belle," you know that B-17s were equipped with manual cranks for lowering the landing gear in case of an emergency. During war time, these planes were always getting shot up and losing their electrical or hydraulic systems, and the cranks My hair took a beating, but I got a great picture.

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