Bob, OK - that makes sense. If you follow good analog/digital layout rules then this may not be a problem. But your point about the EFC sensitivity is well taken. But, that is always a problem.
Yes, do a lot of people violate good analog/digital layout rules, especially on the ground planes - yep. This is exactly why I am asking these questions. Even in manufacturer's recommended layout instructions you can find mistakes. Unless you have a dev board that you have used and have the gerbers from that board so you know exactly how that part behaves with that layout - you cannot know for sure you have a sound layout for your design. You also have to be careful with board material, dielectrics, and copper weight, not to mention controlled impedances. Remember the early days of DC/DC converters? Thanks! John / AJ6BC On Wed, Oct 30, 2013 at 5:52 PM, Bob Camp <li...@rtty.us> wrote: > Hi > > Consider that microvolts matter on the EFC. Unless you have a separate > return for the oven current it’s going to be tough to keep everything > separate. One might ask “why no separate return”. Well when you design one > in, and then go look at people’s layouts - you might as well not have > designed it in ….. > > Bob > > On Oct 30, 2013, at 8:37 PM, John C. Westmoreland, P.E. < > j...@westmorelandengineering.com> wrote: > > > Graham and Time Nuts, > > > > (thanks for the answers.) > > > > I have another question - I am looking at a part from MTI. I wanted to > use > > one of their 3.3V parts. They are telling me to use the 12V part because > > the 3.3V part can have an issue with ground loops due to the higher > current > > requirements at that voltage for the oven. > > > > Have any of you experienced this? Makes me wonder a little why they > offer > > the 3.3V part. It would seem good layout can control any possibility of > > ground loops becoming a problem. > > > > Thanks and Regards, > > John W./AJ6BC > > > > > > > > > > On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H <time...@austin.rr.com > >wrote: > > > >> John: > >> > >> All SMT OCXO's will either have a recommended PCB footprint in the spec > >> sheet > >> or will refer you to a recommended footprint in another document. > >> > >> Some don't care about a ground plane under the part, some require it > >> with no crossing signals, some require an open thermal hole underneath > >> the oven. I have seen all three cases. As usual, it is suggested that > you > >> read the [] manual. > >> > >> Best regards, > >> --- Graham / KE9H > >> > >> == > >> > >> > >> > >> On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote: > >> > >>> Hello, > >>> > >>> I was wondering if I could get some recommendations on surface mount > >>> OCXO's > >>> vs. the traditional through hole. > >>> > >>> I was also wondering on the board layout - if you found it necessary to > >>> leave a thermal moat so to speak - and what worked best. Maybe the > OCXO > >>> has an internal air barrier that maybe would make this unnecessary - > not > >>> sure. > >>> > >>> Your input and experience appreciated. > >>> > >>> Thanks, > >>> John Westmoreland > >>> ______________________________**_________________ > >>> time-nuts mailing list -- time-nuts@febo.com > >>> To unsubscribe, go to https://www.febo.com/cgi-bin/** > >>> mailman/listinfo/time-nuts< > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > >>> and follow the instructions there. > >>> > >>> > >> ______________________________**_________________ > >> time-nuts mailing list -- time-nuts@febo.com > >> To unsubscribe, go to https://www.febo.com/cgi-bin/** > >> mailman/listinfo/time-nuts< > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts> > >> and follow the instructions there. > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.