8.4 Layout

8.4.1 Layout Guidelines

Reflections and matching are closely related to loop antenna theory, but different enough to warrant their

own discussion. When a PCB trace turns a corner at a 90° angle, a reflection can occur. This reflection is

primarily due to the change of width of the trace. At the apex of the turn, the trace width is increased to 1.414

times its width. This upsets the transmission line characteristics, especially the distributed capacitance and

self–inductance of the trace — resulting in the reflection. It is a given that not all PCB traces can be straight, and

so they will have to turn corners. Figure 8-3 shows progressively better techniques of rounding corners. Only the

last example maintains constant trace width and minimizes reflections.

8.4.2 Layout Example

WORST

BETTER

BEST

1W min.

W

Figure 8-3. Trace Example

www.ti.com

CD4051B, CD4052B, CD4053B

SCHS047N – AUGUST 1998 – REVISED FEBRUARY 2025

Copyright © 2025 Texas Instruments Incorporated

Submit Document Feedback

21

Product Folder Links: CD4051B CD4052B CD4053B