Hi > On Dec 24, 2021, at 4:26 AM, Hal Murray <[email protected]> wrote: > > > [email protected] said: >> The gotcha is the common ground found on most OCXO???s. Putting the oven >> current through that ground makes keeping the Vref (and the EFC) well behaved >> a bit of a chore. For various reasons OEM???s have a hard time dealing with >> multiple grounds that have multiple purposes ???. > > That sounds like something a good app-note could solve. > > Is the problem more complicated than that? > Has the app-note not been written? > Do people not read it?
You would think so, but that’s not the case. Even going out and doing a full up presentation about “why” turns out to be inadequate. > ... > > Assuming the pinout on the osc is right... > How much trouble does I*R drop on a ground plane contribute? First up: do you even *have* a ground plane? How many ground layers do you have and how thick are they? How many square feet of board do you have? Is it a double oven with the heaters running on 3.3V? (yikes …) Is the current (even in that 3.3V double oven) completely insignificant compared to each of a dozen other devices on the board? > Do I need to run > a separate trace for the heater return back to the power supply? If you are running traces, yes. If it’s a ground plane, that sort of eliminates the value of the plane. In typical low power designs a top and bottom ground plane should do the job well enough to not need to go super crazy. If you are going to run a trace for something, the negative side of your external Vref (and / or DAC) is what you normally do. Noise issues may not allow you that luxury …. Bob > > -- > These are my opinions. I hate spam. > > > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send an > email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
