５８
2.5.4 10GB LAN Routing Guidelines
10Gb Ethernet Insertion Loss Performance
The 10Gb Ethernet interface to the COM Express connector is the KR interface as specified in the IEEE
802.3-KR Clause 72 and Annex 69B specification. This is the MAC to PHY interface as opposed to the
PHY to connector (magnetic) interface of the 1Gb Ethernet connections.
Typically, the MAC KR interface is connected directly to the PHY. In the case of COM Express, the KR
interface is connected through the COM Express connector to the PHY. The insertion loss performance
must be maintained within the normative channel specification as stated in IEEE 802.3 Annex 69B.
Simulations have shown that the trace length allocations in Table15 meet the required channel
specifications. Proper high speed design techniques must be used. Consult the silicon design guide for
trace clearance and other design rules. High speed guidance for the routing of 10GHz differential pairs is
outside the scope of this document. All differential pairs are routed at 100 Ohms +/-10% differential
impedance Match signals within a pair +/- 5 mils
Figure 15
: 10GBASE-KR Trace Length Budget
Table 15
: 10/100/1000 Ethernet Insertion Loss Budget, 100 MHz
Segment
Length (mils) Notes
L
A
2500
Up to 2.5 inches of Module trace (within Normal FR4)
L
B
5000
Up to 5 inches of Carrier Board trace (within Normal FR4)
Total
7500
