Question about ADC, 6dB/bit and spurious free level...

[Klaus Kragelund]

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Regards

Klaus

 

[server]

On Wed, 4 Nov 2020 14:26:27 -0800 (PST), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Regards

Klaus

It\'s available from Rochester, which suggests EOL. Digikey\'s link to
the TI data sheet doesn\'t work.

But there are probably lots of cheap video ADCs around.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Rickster C]

On Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund wrote:

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Don\'t know that I can help you, but maybe you can explain something to me. You say you need a 14 bit converter, then mention 90 dB and 16 times 6 dB. That\'s three different things that are not equal and yet you seem to be talking aboout them as equivalent. I\'m confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes well with a 16 bit converter, but I don\'t get the 14 bit comment.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Edward Rawde]

\"Rickster C\" <gnuarm.deletethisbit@gmail.com> wrote in message
news:5c4eebd5-36b8-40fb-b0ec-a3901a5d373ao@googlegroups.com...
On Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund wrote:
Hi

I am working on some fun stuff for my own firm. I need a high speed ADC
to acquire a signal up to 25MHz, preferable with high dynamic range in
the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16
times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and
noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost
device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down
to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am
missing?

Hard to say but maybe not. The OP may have meant a 16 bit converter or may
not have given mathematically accurate figures, just near enough.
https://www.google.com/search?&q=db+dynamic+range+bits
So for an 8 bit converter the dynamic range is 48 dB = 48/8 = 6 dB / bit
For a 14 bit converter 20*log10(2^14) = 84 dB = 84/14 = 6 dB / bit
for a 16 bit converter 20*log10(2^16) = 96 dB = 96/16 = 6 dB / bit
But that\'s all theoretical and ADC specs will give figures which take other
device specific parameters into account.

Don\'t know that I can help you, but maybe you can explain something to me.
You say you need a 14 bit converter, then mention 90 dB and 16 times 6 dB.
That\'s three different things that are not equal and yet you seem to be
talking aboout them as equivalent. I\'m confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes well
with a 16 bit converter, but I don\'t get the 14 bit comment.

--

Rick C.

 

[Phil Hobbs]

On 11/5/20 12:15 AM, Edward Rawde wrote:

\"Rickster C\" <gnuarm.deletethisbit@gmail.com> wrote in message
news:5c4eebd5-36b8-40fb-b0ec-a3901a5d373ao@googlegroups.com... On
Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund
wrote:
Hi

I am working on some fun stuff for my own firm. I need a high
speed ADC to acquire a signal up to 25MHz, preferable with high
dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit
converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf



It costs 15 USD, but has power spectrum on page 19 with a nice peak and
noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low
cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7



Page 9 shows the output power spectrum, shows a nice peak and noise down
to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious
I am missing?

Hard to say but maybe not. The OP may have meant a 16 bit converter
or may not have given mathematically accurate figures, just near
enough. https://www.google.com/search?&q=db+dynamic+range+bits So for
an 8 bit converter the dynamic range is 48 dB = 48/8 = 6 dB / bit For
a 14 bit converter 20*log10(2^14) = 84 dB = 84/14 = 6 dB / bit for a
16 bit converter 20*log10(2^16) = 96 dB = 96/16 = 6 dB / bit But
that\'s all theoretical and ADC specs will give figures which take
other device specific parameters into account.

Don\'t know that I can help you, but maybe you can explain something
to me. You say you need a 14 bit converter, then mention 90 dB and
16 times 6 dB. That\'s three different things that are not equal and
yet you seem to be talking aboout them as equivalent. I\'m
confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise
floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes
well with a 16 bit converter, but I don\'t get the 14 bit comment.

Specsmanship again.

There are two cases for considering digitizer carrier-to-noise ratio:
unipolar and bipolar.
Either way, an ideal N-bit ADC (i.e. noiseless and having zero DNL and
INL) contributes quantization noise. In general this is hard to treat,
but as Widrow showed BITD, as long as your signal is at least a few LSBs
in amplitude, the quantization noise can be accurately described as
uniformly-distributed additive white noise of amplitude
(Vref/2**N)/sqrt(12). The sqrt(12) comes from computing the RMS
deviation of a staircase from a straight line--you can derive it in a
few lines of algebra.

In the unipolar case, the signal can have an amplitude right up to Vref,
so the maximum CNR is

CNRmax(dB) = -20*log(2**-N/sqrt(12)) = 6.02 N + 10.79.

In the bipolar case, where the peak-to-peak range of a sine wave has to
fit in [0, Vref), we lose a factor of sqrt(8), so

CNRmax(dB) = -20*log(2**-N * sqrt(8/12)) = 6.02 N + 1.76.

Lower-resolution ADCs sometimes approach these values.

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

 

[Klaus Kragelund]

On Wednesday, November 4, 2020 at 11:43:50 PM UTC+1, jla...@highlandsniptechnology.com wrote:

On Wed, 4 Nov 2020 14:26:27 -0800 (PST), Klaus Kragelund
klau...@hotmail.com> wrote:

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Regards

Klaus
It\'s available from Rochester, which suggests EOL. Digikey\'s link to
the TI data sheet doesn\'t work.

It\'s available from 5 other suppliers also:

https://www.findchips.com/search/ths1060

But, yes, I need to consider longevity

 

[Klaus Kragelund]

On Thursday, November 5, 2020 at 4:35:20 AM UTC+1, Rickster C wrote:

On Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund wrote:
Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?
Don\'t know that I can help you, but maybe you can explain something to me.. You say you need a 14 bit converter, then mention 90 dB and 16 times 6 dB.. That\'s three different things that are not equal and yet you seem to be talking aboout them as equivalent. I\'m confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes well with a 16 bit converter, but I don\'t get the 14 bit comment.

Sorry for that, I was not exact in the OP

It\'s a comparison between the 10bit and the 14bit. So theoretically 60dB vs 84dB

I was just surprised about that the plots from the datasheet showed 90dB noise floor for the 10bit ADC and 100dB for the 14bit. So number don\'t add up?

Cheers

Klaus

 

[Rickster C]

On Thursday, November 5, 2020 at 3:10:13 AM UTC-5, Klaus Kragelund wrote:

On Wednesday, November 4, 2020 at 11:43:50 PM UTC+1, jla...@highlandsniptechnology.com wrote:
On Wed, 4 Nov 2020 14:26:27 -0800 (PST), Klaus Kragelund
klau...@hotmail.com> wrote:

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Regards

Klaus
It\'s available from Rochester, which suggests EOL. Digikey\'s link to
the TI data sheet doesn\'t work.

It\'s available from 5 other suppliers also:

https://www.findchips.com/search/ths1060

But, yes, I need to consider longevity

I\'ve seen things in high volume production sold by Rochester. I don\'t know that everything they make has been abandoned by others. In fact, octopart often reports the lowest prices at Rochester.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Rickster C]

On Thursday, November 5, 2020 at 3:20:16 AM UTC-5, Klaus Kragelund wrote:

On Thursday, November 5, 2020 at 4:35:20 AM UTC+1, Rickster C wrote:
On Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund wrote:
Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?
Don\'t know that I can help you, but maybe you can explain something to me. You say you need a 14 bit converter, then mention 90 dB and 16 times 6 dB. That\'s three different things that are not equal and yet you seem to be talking aboout them as equivalent. I\'m confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes well with a 16 bit converter, but I don\'t get the 14 bit comment.

Sorry for that, I was not exact in the OP

It\'s a comparison between the 10bit and the 14bit. So theoretically 60dB vs 84dB

I was just surprised about that the plots from the datasheet showed 90dB noise floor for the 10bit ADC and 100dB for the 14bit. So number don\'t add up?

Are you sure it showed the numbers you state? I\'ve seen such graphs where the 0dB point was not where you\'d expect it.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[server]

On Thu, 5 Nov 2020 00:20:10 -0800 (PST), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

On Thursday, November 5, 2020 at 4:35:20 AM UTC+1, Rickster C wrote:
On Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund wrote:
Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?
Don\'t know that I can help you, but maybe you can explain something to me. You say you need a 14 bit converter, then mention 90 dB and 16 times 6 dB. That\'s three different things that are not equal and yet you seem to be talking aboout them as equivalent. I\'m confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes well with a 16 bit converter, but I don\'t get the 14 bit comment.

Sorry for that, I was not exact in the OP

It\'s a comparison between the 10bit and the 14bit. So theoretically 60dB vs 84dB

I was just surprised about that the plots from the datasheet showed 90dB noise floor for the 10bit ADC and 100dB for the 14bit. So number don\'t add up?

At least with audio ADCs and DACs it seems to be common to quote the
SNR on the 0-20 kHz bandwidth only even with 192 kHz sampling rate.
The noise shaping helps to get nice numbers for the specification .

 

[server]

On Thursday, 5 November 2020 08:20:16 UTC, Klaus Kragelund wrote:

On Thursday, November 5, 2020 at 4:35:20 AM UTC+1, Rickster C wrote:
On Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund wrote:
Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?
Don\'t know that I can help you, but maybe you can explain something to me. You say you need a 14 bit converter, then mention 90 dB and 16 times 6 dB. That\'s three different things that are not equal and yet you seem to be talking aboout them as equivalent. I\'m confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes well with a 16 bit converter, but I don\'t get the 14 bit comment.

Sorry for that, I was not exact in the OP

It\'s a comparison between the 10bit and the 14bit. So theoretically 60dB vs 84dB

I was just surprised about that the plots from the datasheet showed 90dB noise floor for the 10bit ADC and 100dB for the 14bit. So number don\'t add up?

Noise spectrum plots show the noise spectral density. To get the signal
to noise ration you need to add up the noise components in each frequency
bin in the correct way (which generally relies on the assumption that
the noise in each bin is uncorrelated with that in other bins).
The \"noise floor\" on such plots depends on the measurement bandwidth of
the frequency analyser (often an FFT) used to generate the plot.
John

 

[Phil Hobbs]

On 11/4/20 5:43 PM, jlarkin@highlandsniptechnology.com wrote:

On Wed, 4 Nov 2020 14:26:27 -0800 (PST), Klaus Kragelund
klauskvik@hotmail.com> wrote:

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Regards

Klaus

It\'s available from Rochester, which suggests EOL. Digikey\'s link to
the TI data sheet doesn\'t work.

Rochester seems to be expanding into \'life cycle management\', i.e.
functioning effectively as a second source for parts that are still
active but may be getting old enough that you\'d worry about continued
supply. A smart idea if so. One good thing about them is that unlike
some of the grey-market outfits, they buy enough stock that they don\'t
need to jack up the price as the supply shrinks.

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

 

[server]

On Thu, 5 Nov 2020 11:50:49 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 11/4/20 5:43 PM, jlarkin@highlandsniptechnology.com wrote:
On Wed, 4 Nov 2020 14:26:27 -0800 (PST), Klaus Kragelund
klauskvik@hotmail.com> wrote:

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Regards

Klaus

It\'s available from Rochester, which suggests EOL. Digikey\'s link to
the TI data sheet doesn\'t work.

Rochester seems to be expanding into \'life cycle management\', i.e.
functioning effectively as a second source for parts that are still
active but may be getting old enough that you\'d worry about continued
supply. A smart idea if so. One good thing about them is that unlike
some of the grey-market outfits, they buy enough stock that they don\'t
need to jack up the price as the supply shrinks.

Cheers

Phil Hobbs

A lot of Digikey and Mouser parts are from Rochester lately. I hope
that doesn\'t tag EOL for those parts.

They may be in the reel-breaking business, which is fine.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Edward Rawde]

\"Phil Hobbs\" <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:c87ff8a1-2adb-b675-6f70-b00100e180c8@electrooptical.net...

On 11/5/20 12:15 AM, Edward Rawde wrote:
\"Rickster C\" <gnuarm.deletethisbit@gmail.com> wrote in message
news:5c4eebd5-36b8-40fb-b0ec-a3901a5d373ao@googlegroups.com... On
Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund
wrote:
Hi

I am working on some fun stuff for my own firm. I need a high
speed ADC to acquire a signal up to 25MHz, preferable with high
dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit
converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

[snip]

Specsmanship again.

There are two cases for considering digitizer carrier-to-noise ratio:
unipolar and bipolar.
Either way, an ideal N-bit ADC (i.e. noiseless and having zero DNL and
INL) contributes quantization noise. In general this is hard to treat,
but as Widrow showed BITD, as long as your signal is at least a few LSBs
in amplitude, the quantization noise can be accurately described as
uniformly-distributed additive white noise of amplitude
(Vref/2**N)/sqrt(12). The sqrt(12) comes from computing the RMS
deviation of a staircase from a straight line--you can derive it in a
few lines of algebra.

In the unipolar case, the signal can have an amplitude right up to Vref,
so the maximum CNR is

CNRmax(dB) = -20*log(2**-N/sqrt(12)) = 6.02 N + 10.79.

In the bipolar case, where the peak-to-peak range of a sine wave has to
fit in [0, Vref), we lose a factor of sqrt(8), so

CNRmax(dB) = -20*log(2**-N * sqrt(8/12)) = 6.02 N + 1.76.

Thanks, that made me dig out John Watkinson\'s Introduction to Digital Audio.
It\'s on page 46.

Lower-resolution ADCs sometimes approach these values.

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

 

[Phil Hobbs]

On 11/5/20 12:31 PM, jlarkin@highlandsniptechnology.com wrote:

On Thu, 5 Nov 2020 11:50:49 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 11/4/20 5:43 PM, jlarkin@highlandsniptechnology.com wrote:
On Wed, 4 Nov 2020 14:26:27 -0800 (PST), Klaus Kragelund
klauskvik@hotmail.com> wrote:

Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?

Regards

Klaus

It\'s available from Rochester, which suggests EOL. Digikey\'s link to
the TI data sheet doesn\'t work.

Rochester seems to be expanding into \'life cycle management\', i.e.
functioning effectively as a second source for parts that are still
active but may be getting old enough that you\'d worry about continued
supply. A smart idea if so. One good thing about them is that unlike
some of the grey-market outfits, they buy enough stock that they don\'t
need to jack up the price as the supply shrinks.

Cheers

Phil Hobbs

A lot of Digikey and Mouser parts are from Rochester lately. I hope
that doesn\'t tag EOL for those parts.

They may be in the reel-breaking business, which is fine.

Their minimum order is $250 per item IIRC. (It might be $250 total.)
That reduces the small-quantity nuisance.

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

 

[boB]

On Thu, 05 Nov 2020 12:55:50 +0200, upsidedown@downunder.com wrote:

On Thu, 5 Nov 2020 00:20:10 -0800 (PST), Klaus Kragelund
klauskvik@hotmail.com> wrote:

On Thursday, November 5, 2020 at 4:35:20 AM UTC+1, Rickster C wrote:
On Wednesday, November 4, 2020 at 5:26:33 PM UTC-5, Klaus Kragelund wrote:
Hi

I am working on some fun stuff for my own firm. I need a high speed ADC to acquire a signal up to 25MHz, preferable with high dynamic range in the range of 80 dB

Initially I was thinking to get 90dB, I would need a 14 bit converter (16 times 6dB per bit)

For example the ADS4142 14bit converter:

https://www.analog.com/media/en/technical-documentation/data-sheets/225916fa.pdf

It costs 15 USD, but has power spectrum on page 19 with a nice peak and noise -100dB down

Then I looked at the 3USD part, THS1060, just to see what a low cost device could do:

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am missing?
Don\'t know that I can help you, but maybe you can explain something to me. You say you need a 14 bit converter, then mention 90 dB and 16 times 6 dB. That\'s three different things that are not equal and yet you seem to be talking aboout them as equivalent. I\'m confused.

Did you mean 16 bits and the 16 bit device has a 90 dB noise floor?

Various specs typically don\'t match the 6 dB per bit, so 90 dB goes well with a 16 bit converter, but I don\'t get the 14 bit comment.

Sorry for that, I was not exact in the OP

It\'s a comparison between the 10bit and the 14bit. So theoretically 60dB vs 84dB

I was just surprised about that the plots from the datasheet showed 90dB noise floor for the 10bit ADC and 100dB for the 14bit. So number don\'t add up?

At least with audio ADCs and DACs it seems to be common to quote the
SNR on the 0-20 kHz bandwidth only even with 192 kHz sampling rate.
The noise shaping helps to get nice numbers for the specification .

That may be because if they spec\'d at the higher bandwidth, the noise
would be worse.

Audio equipment specs kind of misleading these days and most pro
audio specs seem to be A-weighted to get better numbers.

Didn\'t used to be like that before around 1995 or so ?

 

[Kevin Aylward]

\"Edward Rawde\" wrote in message news:ro01pf$16oo$1@gioia.aioe.org...

https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A0002213893/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and noise
down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I am
missing?

Hard to say but maybe not. The OP may have meant a 16 bit converter or may
not have given mathematically accurate figures, just near enough.
https://www.google.com/search?&q=db+dynamic+range+bits
So for an 8 bit converter the dynamic range is 48 dB = 48/8 = 6 dB / bit

Oh dear..... unfortunately a common misunderstanding.

The dynamic range is the (maximum coded analog signal)/(minimum coded analog
signal).

The minimum coded signal is *1/2* lsb, not 1 lsb. That is any, analog signal
over 1/2 lsb is a valid code that is actually detected as a 1 lsb. Any
signal below 1/2 lsb is ignored. This means that the dynamic range of an 8
bit converter is:

DR = log(255/(1/2)) = 54.1 dB

The dynamic range should not be confused with the resolution or error.


-- Kevin Aylward
http://www.anasoft.co.uk - SuperSpice
http://www.kevinaylward.co.uk/ee/index.html

 

[Steve Wilson]

\"Kevin Aylward\" <kevinRemovAT@kevinaylward.co.uk> wrote:

\"Edward Rawde\" wrote in message news:ro01pf$16oo$1@gioia.aioe.org...



https://4donline.ihs.com/images/VipMasterIC/IC/TXII/TXII-S-A00022138
93/TXII-S-A0002214048-1.pdf?hkey=EC6BD57738AE6E33B588C5F9AD3CEFA7

Page 9 shows the output power spectrum, shows a nice peak and
noise down to -90dB

Seems like not a big difference in performance.

I have never down high speed acquisition before. Anything obvious I
am
missing?

Hard to say but maybe not. The OP may have meant a 16 bit converter or
may not have given mathematically accurate figures, just near enough.
https://www.google.com/search?&q=db+dynamic+range+bits
So for an 8 bit converter the dynamic range is 48 dB = 48/8 = 6 dB /
bit

Oh dear..... unfortunately a common misunderstanding.

The dynamic range is the (maximum coded analog signal)/(minimum coded
analog signal).

The minimum coded signal is *1/2* lsb, not 1 lsb. That is any, analog
signal over 1/2 lsb is a valid code that is actually detected as a 1
lsb. Any signal below 1/2 lsb is ignored. This means that the dynamic
range of an 8 bit converter is:

DR = log(255/(1/2)) = 54.1 dB

The dynamic range should not be confused with the resolution or error.


-- Kevin Aylward
http://www.anasoft.co.uk - SuperSpice
http://www.kevinaylward.co.uk/ee/index.html

6.02 * numbits:

<https://en.wikipedia.org/wiki/Dynamic_range>

<https://web.archive.org/web/20160407163817if_/https://www.meridian-
audio.com/meridian-uploads/ara/coding2.pdf>

<https://www.analog.com/media/en/training-seminars/tutorials/MT-003.pdf>

I don\'t know how you managed to escape my plonk file, but back you go
again.

PLONK


--
Science teaches us to trust. - sw