I merely used the evaluation board which has a capacitively coupled input. The transformer coupled input circuit using a 1:4 (turns ratio) step up transformer as depicted on the datasheet should reduce the PN floor by at least 3dB for 10MHz input.
Bruce > On July 29, 2014 at 7:30 AM "David C. Partridge" > <[email protected]> wrote: > > > Bruce, > > Thank you, that was very useful information. If I ever do a re-spin of the > divider I will likely use the LTC6957-3 or -4 instead of the ADCMP600 (I > would need interest for at least 40 boards to be able to do this at anything > like an economic price). > > Will you be putting the full details of the circuit you used up on Didier's > web site? Did you use a transformer based circuit similar to Design Note > 514 or just an input capacitor? > > Regards, > David Partridge > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of [email protected] > Sent: 29 July 2014 12:00 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Sine to square wave converter Phase Noise > > Sorry, I meant the LTC6957-4 of course._SELA = l FILTA = L FILTB = H ie an > input stage BW of 160MHz as recommended for a 10MHz + 10dBm input. > > Input for the HX4210 was +14dBm. > > Comparator was that used in David Partridge's programmable divider (includes > the > 74AC04 buffers). > > Bruce > > > On July 29, 2014 at 5:37 AM Magnus Danielson > > <[email protected]> > > wrote: > > > > > > You alternate LTC7957-4 and LTC6957-4 and it is only the later that > exists. > > > > The LTC6957-4 has a single-stage amplifier stage input, with somewhat > > programmable bandwidth. I assume you used the 50 MHz BW setting. > > > > Cheers, > > Magnus > > > > On 07/29/2014 10:55 AM, [email protected] wrote: > > > Recently I have been comparing the phase noise of the HOlzworth > > > HX4210 and the LTC7957-4. > > > I have found that the performance of these devices is comparable > > > with a 10MHz sinewave input with a PN noise floor below -160dBc/Hz. > > > For offsets below 100Hz the LTC6957-4 is quieter and for offsets > > > below 50Hz or so is lower than that of my measurement setup. > > > I merely mounted the LTC evaluation board in a diecast metal box to > > > reduce the effect of air currents on the LTC7957-4 and used an ultra > > > low noise 3.3V power supply (Abracon) to minimise the power supply > > > contribution to the measured phase noise. > > > Achieving a phase noise performance equal to that on the datasheet > > > was relatively easy. > > > In fact for low offsets the phase noise is lower than that shown on > > > the datasheet. > > > > > > I've also measured the phase noise of a comparator based sine to > > > CMOS converter and its PN floor is about 20dB higher than that of > > > the LTC6957. > > > On completion of measurements PN plots for the various sine to > > > square conveters tested will be added to the web pages I maintain on > > > Didiers site.. > > > > > > > > > Bruce > > > _______________________________________________ > > > 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. > _______________________________________________ > 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.
