I doubt the AD5791 does much better than 16 bits operating at 1 Msps, when you include glitch energy, noise, and distortion.
On Saturday, 23 July 2016, Attila Kinali <[email protected]> wrote: > On Fri, 22 Jul 2016 12:15:25 -0500 > David <[email protected] <javascript:;>> wrote: > > > If you expect analog specifications in line with the claimed digital > > resolution of ADCs and DACs, you will be disappointed. 20 bits is > > about where they top out no matter how many bits are available; the > > best you can hope for is that they are monotonic but how meaningful is > > that when it is buried in noise? > > Depends on your application. If the circuitry that follows the DAC has > some integrative/low-pass characteristics, then bits burried in noise > might be not that bad. E.g. when controlling an VCXO, any noise beyond > 10-50kHz will be filtered out by the crystal and its high Q. > > Similarly, low frequency noise might be eaten up by the surrounding > control-loop. This is especially beneficial when dealing with a > circuit that has high 1/f noise. The drawback is, that high loop frequency > (something around 10-100Hz is the minimum required to filter 1/f noise) > is not that easy to achieve. It requires carefull design and makes things > generally a lot more expensive. > > > The LTC2400 is considered suitable for 6 digit designs before software > > calibration is used which the application note and datasheet mention. > > In this case, it is its repeatable INL which can be corrected for and > > its low gain and offset drift which matter. > > Yes, but the LTC2400, as all delta-sigma converters, has the big problem > that it only reaches the full performance at a very low sampling rate. > In case of the LTC2400 it's a whooping 7sps. Ie, that would limit the > DAC build with an LTC2400 in its feedback path to at most 3sps, probably > even lower. > > On the other hand, a modern DACs like the AD5791 reaches full 20bit at > 1Msps > (resp 1us settling time to 0.02% @10V step, or 1us to 1LSB @500 code step). > But using the AD5791 in a design isn't easy either. The dual voltage > reference > that is required to reach full spec is kind of inconvenient. And as phk > already > wrote, these DACs deliver you the reference accuracy and noise very > precisely. > > A nice write-up on issues in this area can be found at[1] > > Attila Kinali > > > [1] "The 20-Bit DAC Is the Easiest Part of a 1-ppm-Accurate Precision > Voltage Source", by Maurice Egan, 2010 > http://www.analog.com/library/analogdialogue/archives/44-04/ad5791.html > > > -- > Malek's Law: > Any simple idea will be worded in the most complicated way. > _______________________________________________ > time-nuts mailing list -- [email protected] <javascript:;> > 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.
