Path: ...!Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Wed, 05 Jun 2024 17:56:18 +0000 From: john larkin Newsgroups: sci.electronics.design Subject: Re: AD5791 Date: Wed, 05 Jun 2024 10:56:18 -0700 Message-ID: References: User-Agent: ForteAgent/8.00.32.1272 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 43 X-Trace: sv3-rNF/C7nVKUlvm31wN1RG7ZrLPKAdy+xIfJKb9FWnjSD3aXxMtjvhyn/Czlnnz8styrNhRzrOna+GFYu!IbfAfoIyxen3Z3rqzRosS2QLfUMCBlFcuTFCQcqhFQxzDT1ENGGgjd/R6Fvf6G2jetS/ukMXj5jk!jm2sEA== X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 2540 On Wed, 05 Jun 2024 12:50:59 -0400, Joe Gwinn wrote: >On Tue, 04 Jun 2024 13:56:36 -0700, john larkin wrote: > >>On Tue, 4 Jun 2024 21:53:13 +0200, Jeroen Belleman >> 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.