9883 datasheet(34/56 Pages) INTEL

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LXT9883/9863 — Advanced 10/100 Unmanaged Repeater

Datasheet

Document #: 249115

Revision #: 003

Rev. Date: 08/07/01

4.2.4

Chassis Ground

For ESD protection, create a separate chassis ground. For isolation, encircle the board and place a

“moat” around the signal ground plane to separate signal ground from chassis ground. Chassis

ground should extend from the RJ-45 connectors to the magnetics, and can be used to terminate

unused signal pairs (‘Bob Smith’ termination). In single-point grounding applications, provide a

single connection between chassis and circuit grounds with a 2kV isolation capacitor. In multi-

point grounding schemes (chassis and circuit grounds joined at multiple points), provide 2kV

isolation to the Bob Smith termination.

4.2.5

The RBIAS Pin

The LXT98x3 requires a 22.1 k

Ω, 1% resistor directly connected between the RBIAS pin and

ground. Place the RBIAS resistor as close to the RBIAS pin as possible. Run an etch directly from

the pin to the resistor, sink the other side of the resistor, and surround the RBIAS trace with a

filtered ground. Do not run high-speed signals next to RBIAS.

9883 Datasheet(PDF) 34 Page - Intel Corporation