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Altera_Forum's avatar
Altera_Forum
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14 years ago

Slow slew rate option versus ballast resistors ?

Typically in the past I have used 22 ohm source resistors to damp ringing on long trace or cable lengths. I was just wondering if the slow slew rate option is a substitute for the 22 ohm ballast resi...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

If you have access to an IBIS simulator you can simulate the output with different slew rate configurations and see what kind of ringing you get. If you have a ready made PCB with series resistors and the same ribbon cable you can also replace the resistors with 0 ohm shunts and experiment yourself.

It is difficult to give a general answer, as it can vary from case to case, but I generally find that keeping some series resistors is more flexible.