DM9081 データシートの表示（PDF） - Davicom Semiconductor, Inc.

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DM9081

10 BASE-T hub controller

Davicom Semiconductor, Inc. 

DM9081

10BASE-T Hub Controller

Power Plane

The board power planes must be separated into

analog and digital portions. The +5V and ground

planes can be laid out according to the configuration

shown in Figure 8. The analog portion should be

located under the analog power pins of the DM9081

chip and the AUI logic. The digital portion should be

located close enough to the 10BASE-T filter to attach

a 0.1mF capacitor to the filter ground pin. Extending

the digital power plane under the 10BASE-T filter is

not recommended. The analog and digital power

planes should be connected at a single point with

either a 1.8-2.2Ω or 120Z ferrite bead. In the diagram

below, a 47mF capacitor is used in parallel with a

0.1mF capacitor to connect the analog and digital

planes. Shielded RJ-45 connectors are

recommended. The shielded pins should be tied to

the frame ground. Depending on the characteristics

of the 10BASE-T filter, either the frame ground or a

void in the planes should be extended under the

filters. Consult the filter manufacturer to determine if

the frame ground is needed to minimize the effects of

cross-talk within the filters.

Figure 8. DM9081 Device Power Plane Recommendations

20

Final

Version: DM9081-DS-F02

February 02, 2001

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