Kontron COMe Starterkit Eval T2 - Manual (Page 98)

COM Express Interfaces
2.11.3. Routing Considerations
Route LVDS signals as differential pairs (excluding the five single-ended support signals), with a
100-Ω differential impedance and a 55-Ω, single-ended impedance. Ideally, a LVDS pair is
routed on a single layer adjacent to a ground plane. LVDS pairs should not cross plane splits.
Keep layer transitions to a minimum. Reference LVDS pairs to a power plane if necessary. The
power plane should be well-bypassed.
Length-matching between the two lines that make up an LVDS pair (“intra-pair”) and between
different LVDS pairs (“inter-pair”) is required. Intra-pair matching is tighter than the inter-pair
matching.
All LVDS pairs should have the same environment, including the same reference plane and the
same number of vias.
LVDS routing rules are summarized in 6.5.9. 'LVDS Trace Routing Guidelines' on page 189
below.
PICMG ® COM Express ® Carrier Board Design Guide Rev. 2.0 / December 6, 2013
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