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Altera_Forum
Honored Contributor
9 years agonanoseconds. Note that there is large variation in delays, so your ring oscillator could have very large frequency differences over PVT(which is why ring oscillators are not recommended except for corner cases where you're doing some non-synchronous circuit). So if asked about ring oscillators, I lead off by saying, "Don't do it", but if you really want to, I put together the following document:
http://www.alterawiki.com/wiki/ring_oscillator