In this article, the relationship between corner wiring and noise is explained. In succession to the previous article, the discussion is not limited to step-up DC/DC converters, but relates to PCBs in general, and so should be considered an aspect of the basics of board layout.
Relationship Between Corner Wiring and Noise
Wiring must have corners (turns, bends), but EMI is greater or smaller depending on the types of bending. This is one secret to the art of wiring.
The diagram below illustrates better and worse corner wiring. If wiring at a corner is bent at a right angle, the impedance change at the corner is large. In this case, distortion occurs in the current waveform, and a waveform disturbance called reflection occurs. In wiring that carries high-frequency signals such as switching nodes, reflection can cause an increase in EMI.
Rather than bending corner wiring at a right angle, it is preferable for it to be bent at 45° or in arc shapes. The larger the bending radius, the smaller is the change in impedance.
・Corner wiring should describe arc shapes so that the change in wiring impedance is smaller, and noise is not generated.