Kontron COMe Starterkit Eval T2 - Manual (Page 187)

Carrier Board PCB Layout Guidelines
6.5.7. LAN Trace Routing Guidelines
Table 66: LAN Trace Routing Guidelines
Parameter Trace Routing
Signal length allowance for the COM Express Carrier
Board 5.0 inches from the COM Express Module to the magnetics
Module
Maximum signal length between isolation magnetics
Module and RJ45 connector on the Carrier Board 1.0 inch
Differential Impedance 95 Ω +/-20%
Single-ended Impedance 55 Ω +/-15%
Trace width (W) PCB stack-up dependent
Spacing between differential pairs (intra-pair) (S) PCB stack-up dependent
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
Length matching between differential pairs (intra-pair) Max. 5mils
Length matching between RX and TX pairs (inter-pair) Max. 30mils
Spacing between digital ground and analog ground plane
(between the magnetics Module and RJ45 connector) Min. 60mils
Spacing from edge of plane Min. 40mils
Via Usage Max. of 2 vias on TX path
Max. of 2 vias on RX path
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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