A couple tricks I've learned along the way: 1) If using a switching supply is required to get a higher voltage, follow it with a good LDO to reduce the noise level. I've done this successfully for powering handheld radio microphones with built-in amplification, video amplifiers, and for operating a GPS receiver and antenna. 2) If there is a possible ground current path problem, break the ground path by using a unity gain "difference" amplifier like the AD8276, or a difference amplifier with gain like the INA145. The input is differential to the source signal, and the output has a moderately high impedance reference terminal that can be tied directly to the load device ground pin. I use this technique all the time to keep down the noise when driving remote analog loads that have large ground currents themselves. (Picture a 110W 40MHz transmitter running off 12V, at the bottom of a stack of other transceivers in the trunk of a police car - with 40A of lights flashing, etc.)
Bob LaJeunesse >________________________________ > From: "John C. Westmoreland, P.E." <[email protected]> >To: Discussion of precise time and frequency measurement <[email protected]> >Sent: Wednesday, October 30, 2013 10:54 PM >Subject: Re: [time-nuts] Surface Mount OCXO Questions > > >Graham, > >Good points - yes, I have this part currently in the design: TPS75833KTTT >(LDO from TI) - putting another one down >(just) for the OCXO isn't a problem. > >And a nice 12V rail isn't a problem either since this is for a radio with a >nice 12V source. Could I boost the 3.3V rail to >12V or maybe 5V to 12V - sure - but your point about the switcher is well >taken and I agree. Having a nice, fat, analog >ground plane isn't a problem either. > >And, this is just a 'dev' board so we can do what we need to make the OCXO >work as good as possible. > >From their spec sheet: '... the supply voltage sensitivity and load >sensitivity is 5E-11 for a 5 % change in voltage or >load impedance.' > >Thanks, >John > > > > _______________________________________________ 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.
