Datasheet

WORST
BETTER
BEST
1W min.
W
2W
20
CD4051B , CD4052B , CD4053B
SCHS047I –AUGUST 1998–REVISED SEPTEMBER 2017 www.ti.com
Product Folder Links: CD4051B CD4052B CD4053B
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11 Layout
11.1 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 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 31 shows progressively better techniques of rounding corners. Only the last example
maintains constant trace width and minimizes reflections.
11.2 Layout Example
Figure 31. Trace Example