
IDT
Eighteen Output Differential Buffer w/2 input mux for PCIe Gen1/2/3
1678D—03/23/12
9EX21831
Eighteen Output Differential Buffer w/2 input mux for PCIe Gen1/2/3
10
Common Recommendations for Differential Routing
Dimension or Value
Unit
Figure
L1 length, route as non-coupled 50ohm trace
0.5 max
inch
1
L2 length, route as non-coupled 50ohm trace
0.2 max
inch
1
L3 length, route as non-coupled 50ohm trace
0.2 max
inch
1
Rs
33
ohm
1
Rt
49.9
ohm
1
Down Device Differential Routing
L4 length, route as coupled microstrip 100ohm differential trace 2 min to 16 max
inch
1
L4 length, route as coupled stripline 100ohm differential trace
1.8 min to 14.4 max
inch
1
Differential Routing to PCI Express Connector
L4 length, route as coupled microstrip 100ohm differential trace 0.25 to 14 max
inch
2
L4 length, route as coupled stripline 100ohm differential trace
0.225 min to 12.6 max
inch
2
DIF Reference Clock
HCSL Output Buffer
L1
L1'
Rs
L2
L2'
Rs
L4'
L4
L3
L3'
Rt
PCI Express
Down Device
REF_CLK Input
Figure 1: Down Device Routing
HCSL Output Buffer
L1
L1'
Rs
L2
L2'
Rs
L4'
L4
L3
L3'
Rt
PCI Express
Add-in Board
REF_CLK Input
Figure 2: PCI Express Connector Routing