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EP2S90F1020C5 Datasheet, PDF (751/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1 | |||
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High-Speed Board Layout Guidelines
1 If possible, you should avoid using stubs in your PCB design.
For high-speed designs, even very short stubs can create signal
integrity problems.
Figure 11â14. Daisy Chain Routing with Stubs
Main Bus
Stub
Clock
Source
Termination
Resistor
Device 1
Device 2
Device Pin
(BGA Ball)
Figures 11â15 through 11â17 show the SPICE simulation with different
stub length. As the stub length decreases, there is less reflection noise,
which causes the eye opening to increase.
Figure 11â15. Stub Length = 0.5 Inch
Figure 11â16. Stub Length = 0.25 Inch
Altera Corporation
May 2007
11â15
Stratix II Device Handbook, Volume 2
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