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could cause serious EMI emissions and degrade analog performance due to ground
bounce noise.
The plane area underneath the magnetic module should be left empty. This free area is to
keep transformer induced noise away from the power and system ground planes.
The isolated ground, also called chassis ground, connects directly to the fully shielded
RJ45 connector. For better isolation it is also important to maintain a gap between chassis
ground and system ground that is wider than 60mils. For ESD protection, a 3kV high
voltage capability capacitor is recommended to connect to this chassis ground.
Figure 4: LAN Ground Plane Separation
2.4.6 LAN Link Activity and Speed LED
The Qseven module has four 3.3V push/pull outputs to directly drive activity, speed
indication and link status LEDs. The 3.3V standby voltage should be used as LED supply
voltage so that the link activity can be viewed during system standby state. Since LEDs
are likely to be integrated into a RJ45 connector with integrated magnetics module, the
LED traces need to be routed away from potential sources of EMI noise. Consider adding
a filtering capacitor per LED for extremely noisy situations. The suggested value for this
capacitor is 470pF.
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