2. If not using an RJ45 connector with internal termination for unused cable pairs then terminate with 75 Ohm
resistors to a proper chassis ground plane through a high voltage (2KV) capacitor
.
16.1.3 Ethernet RJ45 Connector Considerations
1. A shielded, metal enclosed RJ45 connector is recommended.
2. The metal shield must be connected to a proper chassis ground plane.
3. Another ESD enhancement may be the use of an RJ45 connector with surface mount contacts. This
may simplify routing and allow greater separation in the Ethernet front end to enhance ESD/susceptibility
performance.
16.1.4 Ethernet Magnetics Considerations
1. Many different types and configurations of magnetics available for use with any particular LAN device.
Different packages, orientations, and sizes are all factors that need to be considered when selecting
magnetics.
Table 16-1. Ethernet Magnetics Selection Criteria
Parameter Value Test Condition
Turns ratio 1 CT : 1 CT -
Open-circuit inductance (minimum) 350 µH 100 mV, 100 kHz, 8 mA
Insertion loss (typical) -1.1dB 100 kHz to 100 MHz
HIPOT (minimum) 1500 Vrms -
2. The magnetics must be placed as close as possible to the RJ45 connector.
3.
Depending on which style of magnetics is selected (North/South or East/West), this will determine the
orientation of the magnetics as related to the RJ45 connector. Be certain the network side of the magnetics
face the RJ45 connector and the device side of the magnetics face the LAN device. This will ensure that the
high voltage barrier through the middle of the magnetics can be correctly routed and designed on the PCB.
Ideally, the LAN device should then be placed as close as possible to the magnetics. If this is not possible,
the RJ45 connector and magnetics must remain in close proximity. The LAN device then can be located
somewhat remotely from the RJ45 or magnetics area.
Return to Checklist
Ethernet
© 2022 Microchip T
echnology Inc.
and its subsidiaries
Manual
DS70005439B-page 62
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