[volt-nuts] Building a high resolution DAC

[Brooke Clarke]

Hi:

I haven't been following this thread but see it's about making a DAC with a lot of bits.
While researching a Quantec GPS receiver I discovered a patent that for a 4 bit DAC to be used to drive a precision 
oscillator.
http://www.prc68.com/I/Q5200.shtml#Patent
It depends on using the carry out from an NCO that has a 48 bit input word.

PS HP/Agilent has some instruments with very high quality programmable DC sources such as the 4352 VCO tester.  These 
have very low noise but I forget how many bits.

Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html
Andreas Jahn wrote:
> Hello,
>
> its not only the plastic (epoxy) package.
> Its also the epoxy PCB which creates package stress to the die.
> And I do not believe that any "slots" make it significantly better.
> Thats why I use the AD586LQ; and soldering only one pin to the PCB.
> (the others with thin VERO-wire).
>
> With best regards
>
> Andreas
>
> Am 17.08.2015 um 18:46 schrieb Daniel Mendes:
>>
>> Look at LT6655 datasheet, page 14, about long term drift of MS8 versus LS8 package. If others refferences are as bad 
>> regarding moisture then i think this may be a problem at this level of accuracy.....
>>
>> Daniel
>>
>> Em 17/08/2015 13:29, Andreas Jahn escreveu:
>>> Hello,
>>>
>>> I would rather use a reference with lower tempco than the LT1021. (typical 7ppm/K)
>>> E.g. (selected) AD586LQ or MAX6350.
>>> Or at least LT1236AILS8 with around 3ppm/K.
>>> The self heating alone gives around 3 deg C temperature difference.
>>>
>>> With best regards
>>>
>>> Andreas
>>>
>>> Am 17.08.2015 um 18:19 schrieb Attila Kinali:
>>>> On Mon, 17 Aug 2015 15:38:37 +0000
>>>> "Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:
>>>>
>>>>
>>>>>> You mean the AD7177-2? That seems to be quite hard to get by.
>>>>> I was thinking of the TI part intended for seismic applications.
>>>> Hmm. The ADS1262 does indeed seem quite easily available.
>>>>>> My goal was to stay below 30-40USD for the whole DAC if possible.
>>>>>> But yes.. it might not be possible.
>>>>> I don't think it is.  The necessary voltage reference will set you
>>>>> back almost that much...
>>>> I thought about using the LT1021. I don't need the long term
>>>> stability of the LTZ1000 and the LT1021 is available for less than 10USD.
>>>>
>>>> But from the discussion here, think i have to go back and see whether
>>>> i really need such an high resolution or whether 20bit wouldnt be already
>>>> enough. Then i could get away with a 20bit DAC like the DAC1220.
>>>>
>>>> Thanks
>>>>
>>>>             Attila Kinali
>>>>
>>>
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