Kontron COMe Starterkit Eval T2 - Manual (Page 177)

Carrier Board PCB Layout Guidelines
6.4. Trace-Length Extensions Considerations
High speed differential signals need controlled impedance and according to the maximum loss
budget a controlled maximum trace length. In some systems the maximum trace length need to
be exceeded on the Carrier Board according to mechanical or system engineering reasons.
Trace-length extensions can be done with special signal conditioning chips from vendors like
Texas Instruments or Pericom, which are available for USB 3.0, SATA and PCIe.
Figure 73: Trace-length extension with signal conditioning chip
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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COM Express Module
COM Express Carrier Board
maximum allowed signal
trace length
signal conditioning chip
additional allowed
trace length
interface
jack
interface
cable
external device