App note: Layout guidelines for DC/DC switching power supplies

Maxim describes how to design PCBs for DC/DC switching power supplies. Learn which traces to keep as short as possible, and the reasoning behind it.

The diagram sums up our own approach nicely as well. When working with any buck or boot converter, we:

  • Keep the main power path (shown in blue) straight and compact. We always use an extra wide trace or even a polygon. It’s surprising how often you find boards that use a dainty 16mil trace, it should be 5 to 10 times bigger.
  • Supply capacitors Cin1 and Cin2 should be as close to the switch input as possible. The switch is usually a FET, in this case it is inside the chip.
  • The buck or boost parts (L1, D, Cout) should be snuggled right up against the switch output in a straight, clean path.  The MAX16974/MAX16975/MAX16976 high-performance DC-DC converters are standard buck controllers designed for automotive applications. This application note explains how to optimize the layout of these ICs. An example layout is provided at the end of the document.

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    1. I took the meaning to be “don’t be afraid to use the biggest/widest trace that will fit.” The voltage drop on small conductors can be surprising, even over short distances.

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