Specifications

Intel
®
810E2 Chipset Platform
R
94 Design Guide
3.21.4.4. Critical Dimensions
There are two dimensions to consider during layout. Distance ‘B’ from the line RJ45 connector to the
magnetics module and distance ‘A’ from the 82562ET or 82562EM to the magnetics module (see the
following figure).
Figure 54. Critical Dimensions for Component Placement
Critical_place_2
ICH2 82562EH
Magnetics
Module
Line
RJ11
B
A
EEPROM
LPF
Phone
RJ11
C
Distance Priority Guideline
A 1 < 1”
B 2 < 1”
Distance from Magnetics Module to RJ45
The distance A in the previous figure should be given the highest priority in board layout. The separation
between the magnetic module and the RJ45 connector should be kept less than 1”. The following trace
characteristics are important and should be observed:
• Differential impedance: The differential impedance should be 100 Ω. The single-ended trace
impedance will be approximately 50 Ω. However, the differential impedance can also be affected by
the spacing between the traces.
• Trace Symmetry: Differential pairs (e.g., TDP and TDN) should be routed with consistent
separation and with exactly the same lengths and physical dimensions (e.g., width).
Caution: Asymmetric and unequal length traces in the differential pairs contribute to common-mode noise. This
can degrade the receive circuit’s performance and contribute to emissions radiated from the transmit
circuit. If the 82562ET must be placed farther than a couple of inches from the RJ45 connector, distance
B can be sacrificed. It should be a priority to keep the total distance between the 82562ET and RJ45 as
short as possible.
Note: The measured trace impedance for layout designs targeting 100 Ω often result in lower actual impedance.
OEMs should verify actual trace impedance and adjust their layouts accordingly. If the actual impedance
is consistently low, a target of 105–110 Ω should compensate for second-order effects.