I'm assuming you are routing the output signal of an oscillator, not the crystal signals themselves.
The rise- & fall-times of the clock signal will determine how long the trace can be without termination. Faster edge-rates, say in the 2-3nsec range, will limit your trace to around 1 inch. Signals propagate around 150psec/inch, and if the rise/fall times are about 10x (or larger) longer than the flight-time, then reflections should not have sufficient amplitude to cause false clocking. In the example above, 1 inch of trace has a round-trip flight-time of 300psec. If the rise and fall delays are 3nsec or larger, you can safely use 1 inch of trace without using termination networks or controlled-impedance traces. SPICE simulations are very helpful when deciding how to design clock lines when you cant satisfy the above rule. On Saturday, December 26, 2020 at 4:06:26 PM UTC-8 Bill van Dijk wrote: > As long as there is not something very noisy on the other side of the > board you’ll be just fine. > > > > Bill > > > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Erick Anderson > *Sent:* Saturday, December 26, 2020 6:53 PM > *To:* neonixie-l <[email protected]> > *Subject:* [neonixie-l] How close together do a controller and crystal > need to be? > > > > > I designed a board for the 6-digit All Spectrum controller, which uses the > Dallas TCXO chip. That's what goes in the DIP-14 socket in the picture. > Right now they're as close to each other as possible. I'm thinking about > redesigning the board to be a bit shorter, and moving the socket into the > empty space at the right of the board would help. This would make the clock > signal trace much longer, but is that actually a problem? > > -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/1bbc978e-4883-4b0e-920f-d5f3ff4c4c2cn%40googlegroups.com > > <https://groups.google.com/d/msgid/neonixie-l/1bbc978e-4883-4b0e-920f-d5f3ff4c4c2cn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/bbe8ae0a-bb3c-4f4a-98f6-9f56bc1e1805n%40googlegroups.com.
