Sujet : Re: AD5791
De : cd999666 (at) *nospam* notformail.com (Cursitor Doom)
Groupes : sci.electronics.designDate : 06. Jun 2024, 01:15:30
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <v3qrii$15knr$1@dont-email.me>
References : 1 2 3 4 5 6
User-Agent : Pan/0.149 (Bellevue; 4c157ba)
On Wed, 05 Jun 2024 14:32:15 -0400, Joe Gwinn wrote:
On Wed, 05 Jun 2024 10:56:18 -0700, john larkin <jl@650pot.com> wrote:
On Wed, 05 Jun 2024 12:50:59 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
>
On Tue, 04 Jun 2024 13:56:36 -0700, john larkin <jl@650pot.com> wrote:
>
On Tue, 4 Jun 2024 21:53:13 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:
>
On 6/4/24 19:48, john larkin wrote:
https://www.analog.com/en/products/ad5791.html
That's an amazing part. 20 bit DAC with 1 PPM accuracy and 0.05 PPM
per degree C tempco.
My main gripe is its 3.4K output impedance, which makes a lot of
Johnson noise. I suppose I could run a bunch in parallel.
But you can power the chip from +/-16V and the LSB can be in the 25uV
ballpark. The Johnson noise of 7.5nV/rtHz doesn't seem so bad then,
does it?
>
Jeroen Belleman
>
That helps some. +-14v is about the limit on the references. We'd have
to divide down to get our +-10v range back, and that would need some
crazy stable resistors.
>
Looks like the other way to get the noise down would be to parallel a
number of DACs. Times 8 channels! Ballpark $100 per DAC, which is
actually feasible.
>
It will of course need crazy-low-noise hyper-stable references.
>
I wonder how ADI tests these parts. I can't buy a 1 PPM accurate DVM.
>
Aren't 6.5-digit DMMs exactly 1PPM?
>
Joe Gwinn
>
I think the best I've seen is something like 4 PPM. For north of $14K.
It might be easier to buy a 1ppm voltage reference and calibrate against
that.
.<https://en.wikipedia.org/wiki/Voltage_reference>
For a product instance:
.<https://voltagestandard.com/001%25-10v-reference> costs $140.
Joe Gwinn
Or if you're short of funds but feeling lucky:
https://www.ebay.co.uk/itm/386121438204?itmmeta=01HZNARNCPT8774B3GGG71T3CA&hash=item59e6a193fc:g:KnAAAOSwBWZlA~l-
&itmprp=enc%3AAQAJAAAA4I%2Fd68mFhvvQ5uDzWpxhkKg5vNDFXKoaX71I7C%2Bqi4X1gEOSl%2ByQi%2Byb2yOKfSu2%2FGOYQPxHJw1jBRs3MIV3zJSRqR7pVAm8aYNVy7wLMnKjXWFN3KSHr6bKCyxJl7bSItVlod4JvVGDybNaYHAoGlJYiRk5MoLu6Ts%2F2qgn36iLDRdrEx31hJOeg1QyKcHTImNsukRBOP7Yl22Bx9YxUiHUfAOCZM815wKloAqWtkq7q7XeVxFJa2zzbrTD68SkZelbZjGcClZiCAa0c3nS8z3CkRuQ%2FXFCitVqwxvlZ2a6%7Ctkp%3ABFBM1Nbiqv1j
AD5791
Re: AD5791