CD54HC4051F3A datasheet(25/49 Pages) TI

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CD54HC4051, CD74HC4051

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SCHS122M – NOVEMBER 1997 – REVISED MAY 2019

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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 in width of the trace. At the apex of the turn, the trace width is increased to 1.414 times its width. This

change in width upsets the transmission line characteristics, especially the distributed capacitance and self-

inductance of the trace, thus resulting in the reflection. Not all PCB traces can be straight, so they will have to

turn corners. Figure 22 shows progressively better techniques of rounding corners. Only the last example (BEST)

maintains constant trace width and minimizes reflections.

11.2 Layout Example

Figure 22. Trace Example

CD54HC4051F3A 数据表(PDF) 25 Page - Texas Instruments