Path: ...!Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Fri, 07 Jun 2024 02:38:12 +0000 From: john larkin Newsgroups: sci.electronics.design Subject: Re: AD5791 Date: Thu, 06 Jun 2024 19:38:12 -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: 47 X-Trace: sv3-5JVXXMZi0sV7AkXIOhSnlu02ng8+I5cLpRE4gkWBIie5lIGkIXzpUVsImfta8YxTGVTdF6/CTof4WAy!xlQYS9lpkgriSdoBDItjZYuwoi3Ri7SQORW/5D3/E7yH6VFliSTEOkMapd0qPsxct/6rWEWSRU6W!eccp4g== 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: 2728 On Thu, 6 Jun 2024 22:19:22 -0400, Phil Hobbs wrote: >On 2024-06-06 13:57, john larkin wrote: >> On Thu, 06 Jun 2024 10:15:45 -0700, boB wrote: >> >>> On Tue, 04 Jun 2024 10:48:00 -0700, 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. >>> >>> >>> Nice part but costs way too much for any products we make. >>> >>> boB >> >> What do you make? >> >> We live on the lunatic fringe of electronics, things that are really >> hard to do, things with extreme exponents. It makes money because it >> has little competition, but the money is a side effect. I do it >> because it's fun. >> >> There must be something cool that we can do with a 1 PPM accurate DAC. >> >> TI has a 20-bit delta-sigma DAC that's about $12, but it's only linear >> to 15 PPM. I don't understand how a d-s DAC or ADC can even be that >> good. It would seem to need femtosecond edge accuracies inside. >> > >I expect that the deterministic part of the jitter gets pushed out to >high frequency by the noise shaping. > >Random jitter you'd have to deal with by averaging. > >Cheers > >Phil Hobbs I was thinking about rise/fall time asymmetry, changing average values as duty cycles squirm all over the place.