Hi One gotcha with any ADC or DAC is going to be the reference. There, you are in the same “get what you pay for” dilemma. Stable and noisy, can do. Quiet and not very stable, can do. Both stable and quiet, not so easy if you want it cheap.
Noise can also be the sigma delta ADC’s weak point. Even at slow rates, some of them need a lot of averages to quiet down. Does this or that design need this or that level of stability or noise? That depends a lot on the approach used. In a GPSDO, cutting down on the EFC range is a great way to “cost reduce” the rest of the circuit in terms of noise and stability. Well made modern OCXO’s don’t drift a lot …. Bob > On Jul 16, 2017, at 2:24 PM, Charles Steinmetz <csteinm...@yandex.com> wrote: > > Bert wrote: > >> We limited to affordable and solderable. >> The LTC1655 was the clear winner because >> of linearity and temperature >> * * * >> Five years later I know no better alternative > > Well, to name just the first one that comes to mind, how about the LTC1650? > Like the 1655, it is available in SO and DIP packages. Its differential > nonlinearity is >2x better than the 1655, it settles 5x faster (4uS vs. 20uS > to 1 LSB) and is nearly 100x (40dB) quieter (30nV/sqrtHz vs. 280). The 1650 > has substantially lower glitch energy, as well (1.8nV-S for the 1650, 12nV-S > for the 1655). > > Not all of the better specs are required for steering an oscillator at GPSDO > rates, but others are a distinct advantage. > > I have not surveyed the field to see what other "SO or easier to solder" DACs > are available with better performance than the 1655, but I'm sure there are > others. > > This is to take nothing away from the 1655 -- I have accounted for thousands > of them in my own designs, and think very highly of it. > > Best regards, > > Charles > > > _______________________________________________ > 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.
