Advantech MMP3-21 Manual do Utilizador descarregar pdf (Página 50)

Advantech SOM-Express Design Guide

50 Chapter 5 Carrier Board Design Guidelines

5.2.3.3 Crossing a plane split

The mistake shown here is where the data lines cross a plane split. This causes

unpredictable return path currents and would likely cause a signal quality failure as

well as creating EMI problems.

Figure 5-10 Violation of Proper Routing Techniques

5.2.3.4 Stubs

A very common routing mistake is shown in Figure 5-11. Here the designer could

have avoided creating unnecessary stubs by proper placement of the pull down

resistors over the path of the data traces. Once again, if a stub is unavoidable in the

design, no stub should be greater than 200 mils. Here is another example where a

stub is created that could have been avoided. Stubs typically cause degradation of

signal quality and can also affect EMI.

Figure 5-11 Creating Unnecessary Stubs

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