Path: ...!local-2.nntp.ord.giganews.com!Xl.tags.giganews.com!local-1.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail
NNTP-Posting-Date: Fri, 07 Jun 2024 23:21:34 +0000
From: boB <boB@K7IQ.com>
Newsgroups: sci.electronics.design
Subject: Re: AD5791
Date: Fri, 07 Jun 2024 16:21:33 -0700
Message-ID: <38576jhctanoekjde2v3khlg8r6qa7nm6j@4ax.com>
References: <vqcu5j9nu9tf051iu0f1grobcehg1pb0rv@4ax.com> <pkr36j5qof981plh40m9aha092pjooo0b9@4ax.com> <olt36jhod2aatccib3g1q2afeptdmampp6@4ax.com> <ab603e30-c36f-b39a-ad2e-0a34f0eced22@electrooptical.net> <vhs46j5a2es1545o6stn16pad1pjca4c3q@4ax.com> <6a51813e-c633-2ac7-b47d-bc38f8e7953e@electrooptical.net>
User-Agent: ForteAgent/8.00.32.1272
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 85
X-Trace: sv3-AymjjHR0QBbrI4O7KZHkcOYhVdOY4kp5sC1mhMJrjbehoEWOzL5TY7lURXWwUId/ItJOpYdprWCCyI6!tY6jJwk2QsWUQNBpscGr093K5RRqUId/P0W+CKchEXZyc7N1n5jH8lTDLiA/SgeHjyGWWl1ppniJ!wIguMk6i
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: 4051

On Fri, 7 Jun 2024 14:28:18 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 2024-06-06 22:38, john larkin wrote:
>> On Thu, 6 Jun 2024 22:19:22 -0400, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>> 
>>> On 2024-06-06 13:57, john larkin wrote:
>>>> On Thu, 06 Jun 2024 10:15:45 -0700, boB <boB@K7IQ.com> wrote:
>>>>
>>>>> On Tue, 04 Jun 2024 10:48:00 -0700, john larkin <jl@650pot.com> 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?

www.midnitesolar.com

This stuff is hard to do also but we have competetion these days,
unfortunately.  20 years ago we had a large market share.
Unfortunately we had partners that had other ideas and that company
turned into a non-profit.

Just hope the Chinese don't ever want to make the kind of things that
you make, John.

>>>>
>>>> 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'm not sure why ADI calls their Sigma-Delta rather than Delta-Sigma.

Delta-Sigma is at least in the correct order for an A/D converter of
these types.

We use those too but the audio converters are plenty good enough.

boB


>>>
>>> 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.
>> 
>
>Yeah, part of which is deterministic and part random.  DAC noise shaping 
>AIUI makes the the DS sum run in a limit cycle even for a fixed code, so 
>that most of the switching junk is up at high frequency where it's 
>easier to filter out.  However, I'm not a delta-sigma expert.
>
>(They call them sigma-deltas for some reason--possibly related to gang 
>insignia.) ;)
>
>Cheers
>
>Phil Hobbs