３９
Table 8
: PCI Express Insertion Loss Budget, 1.25 GHz with Carrier Board PCIe Device
Segment
Loss (dB)
max. Length
[mm/inches]
Notes
L
A
131/5.15
Allowance for 3.46 dB loss @ 0.28 dB / GHz / inch and 1.66 dB crosstalk
allowance.
Coupling caps not included.
Coupling
Caps
1.19 dB loss. From PCI Express Card Electromechanical Spec., Rev.
1.1, parameters (LST
– LSR). Includes crosstalk allowance of 0.79 dB.
L
B
COM Express connector at 1.25 GHz measured value:
0.25 dB loss.
L
C
402/15.85
Allowance for 8.30 dB loss @ 0.28 dB / GHz / inch and a 2.75 dB
crosstalk allowance..
Total
13.2
13.2dB loss
PCI Express Insertion Loss Budget, 2.5 GHz with Carrier Board PCIE Device
For “device down” PCIe Gen 2 operation, the Module PCIe maximum trace length is restricted to 5.0
inches and the Carrier Board maximum trace to 8.0 inches. Shorter lengths will yield additional margin
and are encouraged where possible. Results assumed FR4 dielectrics. Other dielectrics with lower
losses could be considered, but were not simulated.
Table 9
: PCI Express Insertion Loss Budget, 2.5 GHz with Carrier Board PCIe Device
Segment
max. Length
[mm/inches]
Notes
L
A
127/5
Allowance for module trace. Coupling cap effects included within simulation.
L
B
COM Express™ connector simulated at 2.5 GHz.
L
C
203/8
Allowance for Carrier Board trace.
Total
330/13.0
PCIe GEN2 Data clocked architecture
