Intel CHIPSET 820E - Manual (Page 114)

Intel ® 820E Chipset
R
114 Design Guide
2.22.3.5. Critical Dimensions
As shown in the following figure, there are three dimensions to consider during layout: Distance B, from
the line RJ11 connector to the magnetics module; distance C, from the phone RJ11 to the LPF (if
implemented); and distance A, from the Intel
82562EH component to the magnetics module.
Figure 71. Critical Dimensions for Component Placement
IO_subsys_crit_dim_comp_plac
ICH2
Intel®
82562EH
Magnetics
module
Line
RJ11
B
A
EEPROM
LPF
Phone
RJ11
C
Distance Priority Guideline
B 1 <1 inch
A 2 <1 inch
C 3 <1 inch
2.22.3.5.1. Distance from Magnetics Module to Line RJ11
Distance B should be given highest priority and should be less then 1 inch. Regarding trace symmetry,
route differential pairs with consistent separation and with exactly the same lengths and physical
dimensions.
Asymmetry and unequal length in differential pairs contribute to common-mode noise. This can degrade
the receive-circuit performance and contribute to radiated emissions from the transmit side.
2.22.3.5.2. Distance from Intel
®
82562EH Component to Magnetics Module
Due to the high speed of signals present, distance ‘A’ between the Intel 82562EH component and the
magnetics also should be less than 1 inch, but it should be second priority relative to the distance from
the connects to the magnetics module.
In general, any trace section intended for use with high-speed signals should comply with the proper
termination practices. Proper signal termination can reduce reflections caused by impedance mismatches
between devices and trace routes. A signal’s reflection may contain a high-frequency component that
may contribute more EMI than the original signal itself.