Mobile Intel Pentium 4 Processor - M and Intel 845MP/MZ Chipset Platform Design Guide

Mobile Intel

Pentium

4 Processor-M and Intel

845MP/845MZ Chipset Platform

126 Design Guide

Figure 65. LAN_CLK Routing Example

9.10.1.3. Crosstalk Consideration

Noise due to crosstalk must be carefully controlled to a minimum. Crosstalk is the key cause of timing

skews and is the largest part of the t

RMATCH

skew parameter. t

RMATCH

is the sum of the trace length

mismatch between LAN_CLK and the LAN data signals. To meet this requirement on the board, the

length of each data trace is either equal to or up to 0.5 inches shorter than the LAN_CLK trace.

Maintaining at least 100 mils of spacing should minimize noise due to crosstalk from non-PLC signals.

9.10.1.4. Impedances

The motherboard impedances should be controlled to minimize the impact of any mismatch between the

motherboard and the daughtercard. An impedance of 60

Ω ±10% is strongly recommended; otherwise,

signal integrity requirements may be violated.

9.10.1.5. Line Termination

Line termination mechanisms are not specified for the LAN Connect interface. Slew rate controlled

output buffers achieve acceptable signal integrity by controlling signal reflection, over/undershoot, and

ringback. A 33-

Ω series resistor can be installed at the driver side of the interface should the developer

have concerns about over/undershoot. Note that the receiver must allow for any drive strength and board

impedance characteristic within the specified ranges.

9.10.2. General LAN Routing Guidelines and Considerations

9.10.2.1. General Trace Routing Considerations

Trace routing considerations are important to minimize the effects of crosstalk and propagation delays on

sections of the board where high-speed signals exist. Signal traces should be kept as short as possible to

decrease interference from other signals, including those propagated through power and ground planes.

Observe the following suggestions to help optimize board performance.

LAN_CLK

LAN RXD0