[volt-nuts] Building a high resolution DAC

[John Phillips]

At this level even barometric pressure changes con be a problem.

On Mon, Aug 17, 2015 at 10:58 AM, Andreas Jahn <Andreas_-_Jahn at t-online.de>
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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-- 

*John Phillips*