59
2.5.4.1 10GB LAN KR Guidelines
Table 16
: 10GB LAN KR Trace Length Guidelines
Parameter
Main Route Guidelines
Notes
Signal Group
10GB LAN KR
Differential Impedance Target
100Ω±10
Single End
50Ω±10%
Isolation to equivalent pairs
12H (MS) and 5H(DS)
1,2
Isolation to other signal groups
15H (MS) and 7H (DS)
1
Tx/Rx Spacing
15H(MS) and 7H (DS)
1
LA + LB
SOM-5992 Layout Checklist
Lc
Carrier Board Length
Max length of LA+LB+LC
Slot Card:
28”
Device Down:
28”
Length matching
Differential pairs (intra-pair): Max.
±5mls
Reference Plane
GND referencing preferred
Min 40-mil trace edge-to-major plane edge spacing
GND stitching vias required next to signal vias if
transitioning layers between GND layers
Power referencing acceptable if stitching caps are
used
Carrier Board Via Usage
Max. 2 vias per TX trace, Max. 3 vias per RX trace
AC coupling
The AC coupling capacitors for the TX lines are
incorporated on the COM Express Module. The AC
coupling capacitors for RX signal lines have to be
implemented on the customer COM Express Carrier
Board. Capacitor type: X7R, 100nF ±10%, 16V, shape
0402.
3
Notes:
1.H is height above reference plane.
2.Equivalent pairs are TX to TX or RX to RX(Noninterleaved)
3.AC caps are recommended to be placed close to KR device side (avoid placing AC cpas on mid-bus).
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