Did you test the LTC1655 INL? The data sheet says plus or minus 20 counts maximum.
I suspect Linear Technology designed those low DNL high INL parts for just this sort of application where only monotonic behavior really matters. Their equivalent current output DAC costs about twice as much not including a precision transimpedance amplifier but has an INL specification of plus or minus 1 count. Every couple years I consider the design of a digitally adjusted oscillator and do a search for likely parts. I wonder if it would be more cost effective to use an instrumentation ADC to correct a less expensive DAC design like one based on a PWM. On Fri, 30 Dec 2011 17:48:24 -0500 (EST), ewkeh...@aol.com 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, >timen...@n4iqt.com 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 -- 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. _______________________________________________ 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.