• AD5791

    From john larkin@21:1/5 to All on Tue Jun 4 10:48:00 2024
    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.

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  • From Jeroen Belleman@21:1/5 to john larkin on Tue Jun 4 21:53:13 2024
    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

    --- SoupGate-Win32 v1.05
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  • From john larkin@21:1/5 to jeroen@nospam.please on Tue Jun 4 13:56:36 2024
    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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Phil Hobbs on Tue Jun 4 23:12:51 2024
    Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs


    Never mind. The 1 us is the settling time, so the BW is wider than 350 kHz.


    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
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  • From Phil Hobbs@21:1/5 to john larkin on Tue Jun 4 22:58:54 2024
    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just
    about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Tue Jun 4 17:15:03 2024
    On Tue, 4 Jun 2024 22:58:54 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 >kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just >about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs

    Three DACs in parallel with +-16 refs, divided down to +-10, pencils
    out around 3.2 nv/rthz.

    I'm going to need a very good preamp to measure the noise, something
    below 1 nv/rthz. Any ideas?

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to john larkin on Wed Jun 5 01:11:33 2024
    john larkin <jl@650pot.com> wrote:
    On Tue, 4 Jun 2024 22:58:54 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 >> kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just
    about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs

    Three DACs in parallel with +-16 refs, divided down to +-10, pencils
    out around 3.2 nv/rthz.

    I'm going to need a very good preamp to measure the noise, something
    below 1 nv/rthz. Any ideas?



    ;)

    I believe you may have got one in your stocking in January.

    (For others: we sell a nice 20-MHz AC-coupled preamp for noise
    measurements, the LA-20 Lab Amplifier. Works great, and is cheap like borscht.)

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Steve Goldstein@21:1/5 to john larkin on Tue Jun 4 21:16:54 2024
    On Tue, 04 Jun 2024 17:15:03 -0700, john larkin <jl@650pot.com> wrote:

    On Tue, 4 Jun 2024 22:58:54 -0000 (UTC), Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote:

    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 >>kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just >>about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs

    Three DACs in parallel with +-16 refs, divided down to +-10, pencils
    out around 3.2 nv/rthz.

    I'm going to need a very good preamp to measure the noise, something
    below 1 nv/rthz. Any ideas?

    You can't use +-16 references, there's a 2.5V minimum headroom
    requirement (datasheet page 4). The part is tested and guaranteed
    with +-10V references; it's _possible_ the nonlinearity will be a
    little worse if you increase to, say, +-13.5V refs. This is a
    consequence of the design internals. I don't know if this was ever characterized, you'd probably have to check it yourself.


    You asked about testing. I don't know how this specific part is
    tested, but in general there are (at least) a couple of ways.

    Many automatic testers have a super DVM available as a system
    resource, often an HP3458A. This works well but is slow, hence is an
    expensive solution, i.e. it adds a lot of test time (cost).

    Testers also often have a super-precision system DAC against which you
    can make differential measurements. With an in-amp gaining up the
    difference between the system DAC and the DUT (Device Under Test) by
    something like x100 you could use the system's fast ADC - 12 bits
    might even be enough. There might need to be some averaging involved.
    Even with waiting for the in-amp to settle this may still be easier
    and faster than the system DVM.

    Either way, testing to 20 bits takes time, and time costs money.

    Thermocouple effects can become an issue in testing something like
    this. One of the first parts I designed at ADI was a very linear
    custom VFC with very low offset and offset drift specs. I also
    designed and built the trim and test fixtures and needed to use
    high-purity copper wire and Cd-Sn solder as the part dissipated a lot
    of power (it was a chip-and-wire hybrid full of bipolar stuff - this
    was the 1980s, before there was precision analog CMOS). It's probably
    a lesser issue for AD5791 as the power dissipation is much lower than
    my part had. Probably just the Cd-Sn solder would have sufficed as it
    had 1/10 the thermocouple effect against copper compared with Pd-Sn
    solder, but the fixtures were one-offs so I went al -in.

    I think I still have that roll of solder and the special flux. Now
    it's hazmat.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Tue Jun 4 20:50:03 2024
    On Wed, 5 Jun 2024 01:11:33 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

    john larkin <jl@650pot.com> wrote:
    On Tue, 4 Jun 2024 22:58:54 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 >>> kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just >>> about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs

    Three DACs in parallel with +-16 refs, divided down to +-10, pencils
    out around 3.2 nv/rthz.

    I'm going to need a very good preamp to measure the noise, something
    below 1 nv/rthz. Any ideas?



    ;)

    I believe you may have got one in your stocking in January.

    Yes, I forgot somehow. Thanks.

    We'll likely need another, if we go ahead with this project, and I'll
    have the customer buy some too.




    (For others: we sell a nice 20-MHz AC-coupled preamp for noise
    measurements, the LA-20 Lab Amplifier. Works great, and is cheap like >borscht.)

    Cheers

    Phil Hobbs

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to john larkin on Wed Jun 5 14:37:29 2024
    On 5/06/2024 6:56 am, john larkin 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?

    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.

    In fact it needs a stable thin-film array. Provided the thin-film
    resistors are on a common substrate, the divide ratio can be quite a bit
    more stable than the individual resistances which are at the same
    temperature and made of metal despoited at the same time.

    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.

    Very stable four terminal references can be bought - they aren't cheap
    but there's nothing crazy about the prices or availability. You do have
    to be careful of voltage drops in the relevant printed circuit traces -
    I once had to fix a circuit where the voltage reference was grounded at
    the wrong end of trace carrying the return current from a big EPROM.

    The quick fix was soldering a chunk of copper wire onto the track, but
    changing the layout to something closer to star grounding was the long
    term solution.

    I wonder how ADI tests these parts. I can't buy a 1 PPM accurate DVM.

    Not a enough money? No access to liquid helium? NIST seems to have
    managed it in 1984.

    https://www.nist.gov/system/files/documents/calibrations/im-34-2a.pdf

    They were still working on the Josephson junction array 10V reference
    back then

    https://en.wikipedia.org/wiki/Josephson_voltage_standard

    and it back commercially available in 1989.

    --
    Bill Sloman, Sydney


    --
    This email has been checked for viruses by Norton antivirus software. www.norton.com

    --- SoupGate-Win32 v1.05
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  • From Joe Gwinn@21:1/5 to john larkin on Wed Jun 5 12:50:59 2024
    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

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to sgoldHAM@alum.mit.edu on Wed Jun 5 09:20:55 2024
    On Tue, 04 Jun 2024 21:16:54 -0400, Steve Goldstein
    <sgoldHAM@alum.mit.edu> wrote:

    On Tue, 04 Jun 2024 17:15:03 -0700, john larkin <jl@650pot.com> wrote:

    On Tue, 4 Jun 2024 22:58:54 -0000 (UTC), Phil Hobbs >><pcdhSpamMeSenseless@electrooptical.net> wrote:

    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 >>>kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just >>>about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs

    Three DACs in parallel with +-16 refs, divided down to +-10, pencils
    out around 3.2 nv/rthz.

    I'm going to need a very good preamp to measure the noise, something
    below 1 nv/rthz. Any ideas?

    You can't use +-16 references, there's a 2.5V minimum headroom
    requirement (datasheet page 4). The part is tested and guaranteed
    with +-10V references; it's _possible_ the nonlinearity will be a
    little worse if you increase to, say, +-13.5V refs. This is a
    consequence of the design internals. I don't know if this was ever >characterized, you'd probably have to check it yourself.


    Sorry, right, the refs could be 14, to reduce the Johnson noise by
    40%. Then dividing down to +-10 becomes a problem.



    You asked about testing. I don't know how this specific part is
    tested, but in general there are (at least) a couple of ways.

    Many automatic testers have a super DVM available as a system
    resource, often an HP3458A. This works well but is slow, hence is an >expensive solution, i.e. it adds a lot of test time (cost).

    Testers also often have a super-precision system DAC against which you
    can make differential measurements. With an in-amp gaining up the
    difference between the system DAC and the DUT (Device Under Test) by >something like x100 you could use the system's fast ADC - 12 bits
    might even be enough. There might need to be some averaging involved.
    Even with waiting for the in-amp to settle this may still be easier
    and faster than the system DVM.

    Either way, testing to 20 bits takes time, and time costs money.

    Thermocouple effects can become an issue in testing something like
    this. One of the first parts I designed at ADI was a very linear
    custom VFC with very low offset and offset drift specs. I also
    designed and built the trim and test fixtures and needed to use
    high-purity copper wire and Cd-Sn solder as the part dissipated a lot
    of power (it was a chip-and-wire hybrid full of bipolar stuff - this
    was the 1980s, before there was precision analog CMOS). It's probably
    a lesser issue for AD5791 as the power dissipation is much lower than
    my part had. Probably just the Cd-Sn solder would have sufficed as it
    had 1/10 the thermocouple effect against copper compared with Pd-Sn
    solder, but the fixtures were one-offs so I went al -in.

    I think I still have that roll of solder and the special flux. Now
    it's hazmat.

    The super DVMs don't usually offer a scanner option, so we'd probably
    build a test box with an 8 or 9-channel relay scanner for the DVM and
    a super-low noise AC-coupled amp for the noise measurements.

    We use some cute little DPDT telecom relays for stuff like this,
    latching relays to reduce coil-heating thermoelectrics. We could even
    gap-pad the tester PCB to a big aluminum plate to make it isothermal,
    although a few layers of 2oz copper would do that pretty well.

    Test speed wouldn't be a big deal. Overnight test and cal would be OK.
    We're not making ICs!

    That DAC is astounding, which makes it hard to test.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to All on Wed Jun 5 10:56:18 2024
    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.

    --- SoupGate-Win32 v1.05
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  • From Phil Hobbs@21:1/5 to Phil Hobbs on Wed Jun 5 14:06:07 2024
    On 2024-06-04 21:11, Phil Hobbs wrote:
    john larkin <jl@650pot.com> wrote:
    On Tue, 4 Jun 2024 22:58:54 -0000 (UTC), Phil Hobbs
    <pcdhSpamMeSenseless@electrooptical.net> wrote:

    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.



    Its quoted rise time is 1us, corresponding to a 3 dB bandwidth of about 350 >>> kHz, or 550 kHz noise bandwidth.

    With 7.5 nV 1-Hz noise, the total RMS noise should be about 5.6 uV, just >>> about half a LSB at 10V FS.

    Not that shabby.

    Cheers

    Phil Hobbs

    Three DACs in parallel with +-16 refs, divided down to +-10, pencils
    out around 3.2 nv/rthz.

    I'm going to need a very good preamp to measure the noise, something
    below 1 nv/rthz. Any ideas?



    ;)

    I believe you may have got one in your stocking in January.

    (For others: we sell a nice 20-MHz AC-coupled preamp for noise
    measurements, the

    LA22

    Lab Amplifier. Works great, and is cheap like
    borscht.)

    https://hobbs-eo.com/products/la-22-lab-amplifier


    Cheers

    Phil Hobbs



    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Joe Gwinn@21:1/5 to john larkin on Wed Jun 5 14:32:15 2024
    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

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  • From Cursitor Doom@21:1/5 to Joe Gwinn on Wed Jun 5 23:15:30 2024
    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

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  • From boB@21:1/5 to john larkin on Thu Jun 6 10:15:45 2024
    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

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  • From john larkin@21:1/5 to boB on Thu Jun 6 10:57:50 2024
    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?

    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.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Thu Jun 6 19:38:12 2024
    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?

    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.

    --- SoupGate-Win32 v1.05
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  • From Phil Hobbs@21:1/5 to john larkin on Thu Jun 6 22:19:22 2024
    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?

    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

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From Bill Sloman@21:1/5 to john larkin on Fri Jun 7 14:22:25 2024
    On 7/06/2024 3:57 am, 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?

    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.

    "Accuracy" is an interesting word. The waveforms your are working
    aren't actually square waves - with zero edge transition - but have more
    or less exponential rising and falling edges.

    You don't cares if the rising an falling edges have much the same stable
    shape, and if each exponential has effectively got to the rail before
    the next one starts.

    Different rise and fall times complicate the error analysis, which is a
    tedious exercise (and one that I've done from time to time). One of
    engineers I worked with - and interviewed when he was first hired - did
    a six-digit DVM based on delta-sigma principles and he talked me through
    some of the problems during the job interview. I'd met them before on
    less accurate systems, which meant that he impressed the hell out of me.

    He did some very nice work after we hired him - some of it on one of my projects.

    --
    Bill Sloman, Sydney



    --
    This email has been checked for viruses by Norton antivirus software. www.norton.com

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  • From Phil Hobbs@21:1/5 to john larkin on Fri Jun 7 14:28:18 2024
    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?

    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.


    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

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From john larkin@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Fri Jun 7 13:51:17 2024
    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?

    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.


    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

    Looking at the classic d-s architecture, a midscale code will be
    almost a square wave from the feedback quantizer, but near full scale
    the duty cycle will be very small. Edge density will change with input
    signal.

    Every blip has a rise and a fall and they have to be match exactly to
    get the right average.

    Maybe real chips do something else, charge balancing maybe.

    --- SoupGate-Win32 v1.05
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  • From boB@21:1/5 to pcdhSpamMeSenseless@electrooptical. on Fri Jun 7 16:21:33 2024
    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

    --- SoupGate-Win32 v1.05
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  • From Steve Goldstein@21:1/5 to boB on Fri Jun 7 20:38:57 2024
    On Fri, 07 Jun 2024 16:21:33 -0700, boB <boB@K7IQ.com> wrote:

    < snip>

    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

    <snip>

    They were called Delta-Sigma (using the upper-case Greek characters)
    in the original paper by Inose, Yasuda, and Murakami (IRE Trans. Space Electron. Telemetry, vol. 8, pp 205-209, Sep 1962) and in quite a
    number of subsequent papers.

    Whether they're called Sigma-Delta or Delta-Sigma seems to be almost a religious argument.

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  • From boB@21:1/5 to sgoldHAM@alum.mit.edu on Sat Jun 8 20:12:27 2024
    On Fri, 07 Jun 2024 20:38:57 -0400, Steve Goldstein
    <sgoldHAM@alum.mit.edu> wrote:

    On Fri, 07 Jun 2024 16:21:33 -0700, boB <boB@K7IQ.com> wrote:

    < snip>

    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

    <snip>

    They were called Delta-Sigma (using the upper-case Greek characters)
    in the original paper by Inose, Yasuda, and Murakami (IRE Trans. Space >Electron. Telemetry, vol. 8, pp 205-209, Sep 1962) and in quite a
    number of subsequent papers.

    Whether they're called Sigma-Delta or Delta-Sigma seems to be almost a >religious argument.

    We were happy to be able to use real hardware in the late 1980s.
    Crytal Semiconductor at first I think.

    The way I look at it, the delta part is the input and then the sigma
    from decimation and filtering. They worked really well for the time.

    boB

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