Advantech SOM-Express Design Guide
Chapter 5 Carrier Board Design Guidelines
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Figure 5-30 Differential signals route example
Figure 5-31 Bend example
5.7.3.2 Transformer
We recommend using the integrated Magnetic Modules/RJ-45 connectors. If using
the discrete Magnetic Modules and RJ-45 connector, the transformer should be
placed close to the RJ-45 connector to limit EMI emissions. Each differential pair of
data signals is required to be parallel to each other with the same trace length on the
component (top) layer and to be parallel to a respective ground plane. The 49.9
Ω
pull-down resistors for each differential pair are suggested to be located as close to
the transformer as possible. Figure 5-32 and 5-33 show the 10/100M and Gigabit
Ethernet Layout guidelines.
SOM-Express
On board
chip
L3
Differential
Pairs
Differential
Pairs
L1
Carrier board
Transformer
L2
