Advantech MMP3-21 Manual do Utilizador descarregar pdf (Página 69)

Advantech SOM-Express Design Guide

Chapter 5 Carrier Board Design Guidelines 69

1. Differential Impedance: The differential impedance should be 100 #. The

single ended trace impedance will be approximately 50 #; however, the

differential impedance can also be affected by the spacing between the

traces.

2. Trace Symmetry: Differential pairs should be routed with consistent

separation and with exactly the same lengths and physical dimensions (for

example, width).

Distance B: SOM-Express to Transformer (Priority 2)

Distance B from Figure 5-34 should also be designed to extend as short as possible

between devices, be sure not to go over 2.5 inches. The high-speed nature of the

signals propagating through these traces requires that the distances between these

components be closely observed.

SOM-

Express

GBE_MDI[0]+

LAN Connector

GBE_MDI[0]-

RJ45

Magnetic

Module

(Transformer)

B:2.5 inches max

A:1 inches max

GBE_MDI[3]-

GBE_MDI[3]+

Figure 5-34 Critical Dimensions

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 111 112

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Advantech MMP3-21 Manual do Utilizador Página 69