Intel® 820E Chipset
R
106 Design Guide
Figure 67. LAN_CLK Routing Example
LAN_RXD0 LAN_CLK
2.22.1.5. Crosstalk Consideration
Crosstalk-induced noise must be carefully minimized. Crosstalk is the principal cause of timing skews
and is the largest part of the tRMATCH skew parameter.
2.22.1.6. Impedances
Motherboard impedances should be controlled to minimize the effect of any mismatch between the
motherboard and an add-in card. An impedance of 60 Ω ± 15% is strongly recommended. Otherwise, the
signal integrity requirements may be violated.
2.22.1.7. Line Termination
Line termination mechanisms are not specified for the LAN connect interface. Slew rate-controlled
output buffers provide acceptable signal integrity by controlling signal reflection, overshoot/undershoot,
and ringback. A 33- series resistor can be installed at the driver side of the interface, if the developer
has concerns about overshoot/undershoot. Note that the receiver must allow for any drive strength and
board impedance characteristic within the specified ranges.