As far as I know, they make the internally used Vref externally available for a divider, so the EFC input has a natural rejection against fluctuations of it's own Vref. I would recommend using it rather than building your own reference supply. However, a 78xx won't be a good idea at all. An LTZ1000 is a good choise but to expensive and doesn't give you the above mentioned natural rejection. If you absolutely want to use an external reference, the LM399 can be an appropriate choice, at a price of 10$. Today there are a lot other good references at prices around 5$.
Volker Am 01.02.2014 02:03, schrieb Bob Stewart: > Any idea what the usual temperature coefficient is for the VRef output of > the OCXO? I looked under the Trimble label of my spare and found: DOC2127 > and 44/1416. The one I have installed is probably the same. > > > > >> ________________________________ >> From: Bob Camp <li...@rtty.us> >> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency >> measurement <time-nuts@febo.com> >> Sent: Friday, January 31, 2014 6:17 PM >> Subject: Re: [time-nuts] EFC divider resistors >> >> >> Hi >> >> A 7805 has a *rated* temperature coefficient of 2 mv / C. Most parts do way >> better than this. The problem is knowing if you have a good part or not. On >> a 5V part, your reference could be running 400 ppm/C. Since the divider has >> no impact on this number, it over-rides what ever you do with the divider >> resistors. A good voltage reference will set you back about $50 or so. >> >> > _______________________________________________ > 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.
