No free lunch, of course, but I want to avoid dithering DACs. The 18bit DAC (AD5680) is a 16bit+dithering, I think to use the AD5660 + AD5241 (already available) the pot has a tempco of 30ppm/degree and a noise of 14nV/sqr(Hz). Maybe I have to find something better but to make the first try is available.
On Fri, Dec 30, 2011 at 11:48 PM, <[email protected]> wrote: > Over the last two years along with two list members that may want to pipe > in, I have spend a large amount of time on D/A's and we went as far as > developing a test board using the LTC 2440 and testing numerous D/A's > taking in > to consideration performance, solderability, cost, availability and the > winner is LTC 1655 by a long shot, is even available in a DIP with 16 bits > more than you need for any Rb and if you want 20 bits, dithering is an > option. > My testing consistently shows with OCXO's aging that will in most cases > allow operation of an OCXO for 3 years with out intervention. To top it > off > the LTC1655 cost less than $ 10. Testing the old AD 1861 was an eye opener > but considering what its purpose was and its time the best choice. > Bert > > In a message dated 12/30/2011 4:24:37 P.M. Eastern Standard Time, > [email protected] writes: > > The DAC and it's voltage reference looks to be the weak link in the > digital > control and the "simple" goal. The CPU I mentioned before on closer look > doesn't have a good DAC. The 20 bit TI DAC1220 looks better but not sure > you > can find it in the same package as the CPU. The cheap Rb standards with > digital control would not need a DAC and maybe this points to a simpler > GPSDO that doesn't control the XO with analog but corrects it with a DDS > but > again finding them both in one chip is the problem. I have seen OCXO and > DAC > in the same package and even the DDS and OCXO combined but they didn't fit > the simple goal. Not even sure how good they were. I know they are hard to > find. > > Stanley > > > _______________________________________________ > 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.
