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.
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
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
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.
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
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?
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?
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
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.
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.
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.
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.
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
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
Lab Amplifier. Works great, and is cheap like
borscht.)
Cheers
Phil Hobbs
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.
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.htmlBut 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'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.
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
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.
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
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
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.
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.
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.
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
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
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
On Fri, 07 Jun 2024 16:21:33 -0700, boB <boB@K7IQ.com> wrote:
< snip>
<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
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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