Specifications

Intel

810E2 Chipset Platform

Design Guide 89

3.21.3.2. Guidelines for Intel

82562EH Component Placement

Component placement can affect the signal quality, emissions, and temperature of a board design. This

section discusses guidelines for component placement.

Careful component placement can:

• Decrease potential problems directly related to electromagnetic interference (EMI), which could

result in failure to meet FCC 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.

It is important to minimize the space needed for the HomePNA LAN interface, because all other

interfaces will compete for physical space on a motherboard near the connector edge. As with most

subsystems, the HomePNA LAN circuits must be as close as possible to the connector. Thus, it is

imperative that all designs be optimized to fit in a very small space.

3.21.3.3. Crystals and Oscillators

To minimize the effects of EMI, clock sources should not be placed near I/O ports or board edges.

Radiation from these devices may be coupled onto the I/O ports or out of the system chassis. Crystals

should also be kept away from the HomePNA magnetics module to prevent communication interference.

If they exist, the crystal’s retaining straps should be grounded to prevent the possibility of radiation from

the crystal case, and the crystal should lie flat against the PC board to provide better coupling of the

electromagnetic fields to the board.

For noise-free and stable operation, place the crystal and associated discrete components as close as

possible to the 82562EH. Minimize the length and do not route any noisy signals in this area.

3.21.3.4. Phoneline HPNA Termination

The transmit/receive differential signal pair is terminated with a pair of 51.1-Ω (1%) resistors. This

parallel termination should be placed close to the 82562EH. The center, common point between the

51.1-Ω resistors is connected to a voltage-divider network. The termination is shown in the following

figure.