Intel 820E manual Critical Dimensions, Lpf, Eeprom, Distance Priority Guideline

Intel® 820E Chipset

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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

		A	B	C
ICH2	Intel®	Magnetics	Line
	82562EH	module	RJ11
			LPF	Phone
				RJ11
EEPROM
			IO_subsys_crit_dim_comp_plac

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.

114 Design Guide