Thanks for the input Orin! I'm trying to keep this from turning into the monumental effort my GPSDO had turned into, at least for the moment. So it's going to have to accept whatever the buckboard gives it, unless that's not enough. I just want to see what kind accuracy my GPSDO gives on the scope. Later on, I'll give it a decent place to live.
Bob >________________________________ > From: Orin Eman <[email protected]> >To: Robert LaJeunesse <[email protected]>; Discussion of precise time and >frequency measurement <[email protected]> >Sent: Thursday, September 12, 2013 9:40 PM >Subject: Re: [time-nuts] FE-5680A Voltage? > > >Yes, my reading of the datasheet was the same. 18V in would be fine for >15V output. My concern would be how noisy the output would be. I have 9 >of the from China ebay boards here (gave one to my boss to play with). I >should wire one up and take a look. At any rate, I think a turn or two of >the output wires through a ferrite bead would be in order. The data sheet >shows a secondary filter of 3uH/180uF as well which I'd certainly want to >use to feed a 5680A. Shouldn't do any harm, might do some good. > >Orin. > > >On Thu, Sep 12, 2013 at 7:19 PM, Robert LaJeunesse < >[email protected]> wrote: > >> Looking at the LM2596 datasheet the switch transistor saturation voltage >> is 1.5V max at 3A (1.16v typ). That and an educated guess of about 0.25V >> for inductor loss combine to set the minimum difference between input and >> output. The 1.23V reference is about +/-3% accurate, so after setting the >> "buckboard" to 15.00V out (at 25C) expect it to shift at most 0.5V over >> time and temp. Add that to the minimum in-out difference and now you are at >> a minimum safe input of 2.25V above the nominal 15V output, or 17.25V in. >> An old 19V 3A laptop supply might be a good supply to use for this, if you >> were local I'd hand you one. >> >> As for efficiency, that just tells you the amount of heat the regulator, >> plus inductor, plus diode, etc. will throw off. FWIW the datasheet Figure 5 >> indicates you should expect about 88% or better efficiency for 15V out and >> at least 2V higher input voltage. (Doing some switching power supply design >> for a living does help with my understanding of them, but not ever enough!) >> >> Bob LaJeunesse >> >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. > > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
