Kontron COMe Starterkit Eval T2 - Manual (Page 183)

Carrier Board PCB Layout Guidelines
6.5.2. USB Trace Routing Guidelines
Table 62: USB Trace Routing Guidelines
Parameter Trace Routing
Transfer rate / Port 480 MBit/s
Maximum signal line length
(coupled traces) Max. 17.0 inches
Signal length used on COM Express Module (including the
COM Express connector) 3.0 inches
Signal length allowance for the COM Express Carrier
Board 14.0 inches
Differential Impedance 90 Ω +/-15%
Single-ended Impedance 45 Ω +/-10%
Trace width (W) PCB stack-up dependent
Spacing between differential pairs (intra-pair) (S) PCB stack-up dependent
Spacing between pairs-to-pairs (inter-pair) (s) Min. 20mils
Spacing between differential pairs and high-speed periodic
signals Min. 50mils
Spacing between differential pairs and low-speed non
periodic signals Min. 20mils
Length matching between differential pairs
(intra-pair) 150mils
Reference plane GND referenced preferred
Spacing from edge of plane Min. 40mils
Via Usage Try to minimize number of vias
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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