Intel 82547EI, Руководство по конструкции

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82562EZ(EX)/82547GI(EI) Dual Footprint Design Guide
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4.0 Ethernet Component Layout Guidelines
These sections provide recommendations for performing printed circuit board layouts. Good layout
practices are essential to meet IEEE PHY conformance specifications and EMI regulatory
requirements.
4.1 General Layout Considerations for Ethernet Controllers
Critical signal traces should be kept as short as possible to decrease the likelihood of being affected
by high frequency noise from other signals, including noise carried on power and ground planes.
Keeping the traces as short as possible can also reduce capacitive loading.
Since the transmission line medium extends onto the printed circuit board, special attention must
be paid to layout and routing of the differential signal pairs.
Designing for Gigabit operation is very similar to designing for 10 and 100 Mbps. For the
82547GI(EI) Gigabit Ethernet controller, system level tests should be performed at all three speeds.
4.1.1 Guidelines for Component Placement
Component placement can affect signal quality, emissions, and component operating temperature.
This section provides guidelines for component placement.
Careful component placement can:
•
Decrease potential problems directly related to electromagnetic interference (EMI), which
could cause failure to meet applicable government test specifications.
•
Simplify the task of routing traces. To some extent, component orientation will affect the
complexity of trace routing. The overall objective is to minimize turns and crossovers between
traces.
Minimizing the amount of space needed for the Ethernet LAN interface is important because other
interfaces will compete for physical space on a motherboard near the connector. The Ethernet LAN
circuits need to be as close as possible to the connector (see
Figure 5 ).