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Altera_Forum's avatar
Altera_Forum
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12 years ago

The virtual clock about input or output in timing constrain

When we do timing constrain in input or output, usually we need create a virtual clock. My question is, how can I know the phase relation between virtual clock and clock inside the system, in order t...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
12 years ago

Are you making your own board? The PCB engineer should be able to give you that data. If you're buying the board from a 3rd party, you can ask them or possibly get the trace lengths. I've generally seen people do quick calculations off length(and PCB material) alone. I don't remember the number, but I think you could google it and find something. (PCB propogation delays per inch) I found the following:

http://www.eeweb.com/electronics-quiz/pcb-transmission-line-delay

which states:

The rule of thumb used to solve this problem is that the propagation delay of a stripline trace is ~ 180 ps per inch. The propagating delay of a microstrip trace is ~150 ps.