DM9081FP DAVICOM [Davicom Semiconductor, Inc.], DM9081FP Datasheet - Page 20

• Manufacturer Part Number: DM9081FP
• Description: 10BASE-T Hub Controller
• Manufacturer: DAVICOM [Davicom Semiconductor, Inc.]

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
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Figure 8. DM9081 Device Power Plane Recommendations
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.
10BASE-T Hub Controller
Version: DM9081-DS-F02
DM9081
February 02, 2001
Final