65
2.6.4 Gb Ethernet Trace Length Guidelines
Figure 17
: Topology for Ethernet Jack
Table 20
: Ethernet Trace Length Guidelines
Parameter
Main Route Guidelines
Notes
Signal Group
GB, GBE0_MDIx-
Differential Impedance Target
100 Ω ±10%
Single End
55Ω ±10%
Spacing between RX and TX
pairs (inter-pair) (s)
Min. 50mils
Spacing between differential pairs
and high-speed periodic signals
Min. 300mils
Spacing between differential pairs
and low-speed non periodic
signals
Min. 100mils
Spacing between digital ground
and analog ground plane
(between the magnetics Module
and RJ45 connector)
Min. 60mils
LA
Please see the SOM-5992 Layout Checklist
LB
Carrier Board Length;
Max length of LA+LB
COM Express Module to the magnetics Module - 5.0
inches.
Magnetics Module to RJ45 connector - Max. 1.0 inches.
Length matching
Differential pairs (intra-pair): Max.
±2.5 mils
Reference Plane
GND referencing preferred..
Spacing from edge of plane
Min. 40mils
Carrier Board Via Usage
Max. 2 vias.
Notes: