DM9102DEP datasheet(62/70 Pages) DAVICOM

62 / 70 page

Final

Version: DM9102D-DS-F01

May 10, 2006

9. Application Notes

9.1 Network Interface Signal Routing

Place the transformer as close as possible to the RJ-45

connector. Place all the 50Ω resistors as close as possible

to the DM9102D RX± and TX± pins. Traces routed from

RX± and TX± to the transformer should run in close pairs

directly to the transformer. The designer should be careful

not to cross the transmit and receive pairs. As always, vias

should be avoided as much as possible. The network

interface should be void of any signals other than the TX±

and RX± pairs between the RJ-45 to the transformer and

the transformer to the DM9102D. There should be no power

or ground planes in the area under the network side of the

transformer to include the area under the RJ-45 connector

(Refer to Figure 9-4-1 and 9-5). Keep chassis ground away

from all active signals. The RJ-45 connector and any

unused pins should be tied to chassis ground through a

resistor divider network and a 2KV bypass capacitor.

The Band Gap resistor should be placed as physically close

to pin 101 and 102 as possible (refer to Figure 9-1 and 9-2 ).

The designer should not run any high-speed signal near the

Band Gap resistor placement.

9.2 10Base-T/100Base-TX Application

Figure 9-1

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