Hi Are you referring to something like this:
http://www.electronicsweekly.com/Articles/2008/05/01/43680/fast-settling-syn chronous-pwm-dac-filter-has-almost-no.htm as a synchronous filter for the PWM? Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: Tuesday, June 29, 2010 4:07 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] yet another GPSDO design, or so Attila Kinali wrote: > On Tue, 29 Jun 2010 21:32:10 +1200 > Bruce Griffiths<bruce.griffi...@xtra.co.nz> wrote: > > >> Its possible to build a 24 bit resolution D/A using a synchronously >> filtered PWM circuit. >> A pair of PWM outputs and a few relatively low precision resistors and >> capacitors together with a low noise low drift reference are required. >> The technique takes advantage of the fact that the required EFC voltage >> changes slowly and isnt updated at a highg rate. >> The synchronous filter technique eliminates the very long time constant >> RC filters required with an asynchronously filtered PWM waveform. >> > I've thought about that, but i'm afraid that this will add too > much phase noise trough EFC noise. Though, i have not calculated > how much noise this would generate. > > Attila Kinali > How do you conclude that? You don't know what the circuit is and you've never tested it. Ulrich has, and the output noise is very low. Bruce _______________________________________________ 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.