Electronics > Projects, Designs, and Technical Stuff
Adjust data relative to clock
Yansi:
--- Quote from: edavid on January 20, 2020, 09:04:46 pm --- A gate chain can be used to get more delay in a smaller space.
For high resolution tweaking, use a gate chain, but adjust the supply voltage to vary the delay. (This may also need level shifters.)
--- End quote ---
can be used to get delay and also jitter as a bonus, can't it?
ataradov:
At this point I will have to just try a few things and see what works and what does not.
ogden:
--- Quote from: ataradov on January 20, 2020, 09:16:16 pm ---At this point I will have to just try a few things and see what works and what does not.
--- End quote ---
Yes indeed, yet you have to do better than "just try". You need to properly characterize your solution in whole temperature and component tolerance ranges - to avoid picking edge solution which may possibly fail when you least expect it.
ataradov:
Temperature is not as much of a factor, this stuff is going to be operated by humans. I don't care if it fails at -40 C or +85 C. Operators will fail much faster.
I also don't care as much for slow drifts. As long as things stay more or less stable for a few minutes to a few hours at a time, I'm fine.
As long as I get a few distinct sampling points from different settings, it should work.
OwO:
I would say analog switches (or better, RF switches) are preferred because they introduce the least jitter as the signal path is passive. The RF switches I mentioned have very low insertion loss at these frequencies, so no clock buffering is needed (assuming the delay lines are not too lossy).
Length of delay lines will be the biggest problem, especially at lower frequencies and if you want to roll over into the next cycle. You need around 16cm for 1ns of delay. If this is a 4 layer board you can have very thin 50ohm traces, but also consider using a non-50ohm Z0. The dominant loss contributor of the RF switches at low frequencies is the series resistance (the shunt capacitance is 100-200 femtofarads and can be ignored), so using a high Z0 will also reduce loss. On a 2 layer board (1.0mm thick) I would use 0.2mm traces which are 120ohm.
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