Re: [time-nuts] Question about AD9832 "I out Full Scale" (what does it mean?)

[Richard (Rick) Karlquist]

Well, here is response from ADI:

Quote:
If I remember correctly, this part implements a differential DAC current 
source, but only one of the outputs is bonded externally.
In this case, the current settle by Rset should  be divided by 2..., 
which explain your results.

I'll update the DS as soon as this has been confirmed.
Unquote...

This sounded reasonable when I first read it, but then I realized
that what he was talking about would explain a factor of 2 error
in output VOLTAGE, but not current.  So I think he confused himself.

It should be interesting to see if he can "confirm" it.

Stay tuned.

Rick

On 11/18/2016 1:27 AM, David G. McGaw wrote:

There is something wrong with the example.  The output is single-ended,
so using info from the AD9832 data sheet with Rset=3.9K and Rload=300
ohms as shown in the EVB schematic, it should go from 0 to 3.88mA and 0
to 1.16V.  Figure 12 shows only half this, including only about .3V DC
bias instead of .58V.

I apologize.  As a former Analog Devices applications engineer (Digital
Audio Group), I find this data sheet and user guide poorly written.
They have a lot of digital and almost no analog information.

David N1HAC


On 11/17/16 11:09 PM, Richard (Rick) Karlquist wrote:

Trying to figure out what "Iout Full Scale" means on the AD9832.
Some time nuts may have used this one.

On page 7 of this doc:

http://www.analog.com/media/en/technical-documentation/user-guides/UG-313.pdf


It shows the AD9832 output as 572 mV peak to peak
across 300 ohms.  This works out to 1.9 mA peak to
peak current through the resistor.  But Rset on the
board is 3.9K, which is supposed to give a value
for so-called "Iout Full Scale" of 3.878 mA.

I would have thought (just guessing) that peak to
peak output current would be equal to Iout Full
Scale, but it appears to be only half of that.

Can anyone clarify this?

Rick
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Re: [time-nuts] Question about AD9832 "I out Full Scale" (what does it mean?)

[Tim Shoppa]

Bruce, I assume you are talking about Figure 12 of UG-313.

If an LCD scope is not in single shot mode it will show a composite of many
cycles which will hide the stairsteps (especially if the frequency control
word is not a nice round binary number) in the fuzz.

I think the 0.1uF capacitor on IOUT on the evaluation board also helps roll
off the stairsteps.

Tim N3QE

On Thu, Nov 17, 2016 at 11:49 PM, Bruce Griffiths <
bruce.griffi...@xtra.co.nz> wrote:

> With no internal PLL to generate a higher internal frequency than the
> 25MHz MCLK, that 1MHz waveform looks a bit too smooth for an unfiltered
> 1MHz output.
> Bruce
>
> On Friday, 18 November 2016 5:12 PM, Richard (Rick) Karlquist <
> rich...@karlquist.com> wrote:
>
>
>  Trying to figure out what "Iout Full Scale" means on the AD9832.
> Some time nuts may have used this one.
>
> On page 7 of this doc:
>
> http://www.analog.com/media/en/technical-documentation/
> user-guides/UG-313.pdf
>
> It shows the AD9832 output as 572 mV peak to peak
> across 300 ohms.  This works out to 1.9 mA peak to
> peak current through the resistor.  But Rset on the
> board is 3.9K, which is supposed to give a value
> for so-called "Iout Full Scale" of 3.878 mA.
>
> I would have thought (just guessing) that peak to
> peak output current would be equal to Iout Full
> Scale, but it appears to be only half of that.
>
> Can anyone clarify this?
>
> Rick
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Re: [time-nuts] Question about AD9832 "I out Full Scale" (what does it mean?)

[David G. McGaw]

There is something wrong with the example.  The output is single-ended, 
so using info from the AD9832 data sheet with Rset=3.9K and Rload=300 
ohms as shown in the EVB schematic, it should go from 0 to 3.88mA and 0 
to 1.16V.  Figure 12 shows only half this, including only about .3V DC 
bias instead of .58V.


I apologize.  As a former Analog Devices applications engineer (Digital 
Audio Group), I find this data sheet and user guide poorly written.  
They have a lot of digital and almost no analog information.


David N1HAC


On 11/17/16 11:09 PM, Richard (Rick) Karlquist wrote:

Trying to figure out what "Iout Full Scale" means on the AD9832.
Some time nuts may have used this one.

On page 7 of this doc:

http://www.analog.com/media/en/technical-documentation/user-guides/UG-313.pdf 



It shows the AD9832 output as 572 mV peak to peak
across 300 ohms.  This works out to 1.9 mA peak to
peak current through the resistor.  But Rset on the
board is 3.9K, which is supposed to give a value
for so-called "Iout Full Scale" of 3.878 mA.

I would have thought (just guessing) that peak to
peak output current would be equal to Iout Full
Scale, but it appears to be only half of that.

Can anyone clarify this?

Rick
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Re: [time-nuts] Question about AD9832 "I out Full Scale" (what does it mean?)

[Hal Murray]

rich...@karlquist.com said:
> I would have thought (just guessing) that peak to peak output current would
> be equal to Iout Full Scale, but it appears to be only half of that.

> Can anyone clarify this? 

Don't overlook a bug in the data sheet.

The data sheet for the actual part at
  http://www.analog.com/media/en/technical-documentation/data-sheets/AD9832.pd
f
says
  IOUT Full Scale 4 mA nom, 4.5 mA max
  Output Compliance 1.35 V max 3V supply

I didn't find any reference to "peak" on that data sheet, so no peak-to-peak.



-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Question about AD9832 "I out Full Scale" (what does it mean?)

[Bruce Griffiths]

With no internal PLL to generate a higher internal frequency than the 25MHz 
MCLK, that 1MHz waveform looks a bit too smooth for an unfiltered 1MHz output.
Bruce 

On Friday, 18 November 2016 5:12 PM, Richard (Rick) Karlquist 
 wrote:
 

 Trying to figure out what "Iout Full Scale" means on the AD9832.
Some time nuts may have used this one.

On page 7 of this doc:

http://www.analog.com/media/en/technical-documentation/user-guides/UG-313.pdf

It shows the AD9832 output as 572 mV peak to peak
across 300 ohms.  This works out to 1.9 mA peak to
peak current through the resistor.  But Rset on the
board is 3.9K, which is supposed to give a value
for so-called "Iout Full Scale" of 3.878 mA.

I would have thought (just guessing) that peak to
peak output current would be equal to Iout Full
Scale, but it appears to be only half of that.

Can anyone clarify this?

Rick
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[time-nuts] Question about AD9832 "I out Full Scale" (what does it mean?)

[Richard (Rick) Karlquist]

Trying to figure out what "Iout Full Scale" means on the AD9832.
Some time nuts may have used this one.

On page 7 of this doc:

http://www.analog.com/media/en/technical-documentation/user-guides/UG-313.pdf

It shows the AD9832 output as 572 mV peak to peak
across 300 ohms.  This works out to 1.9 mA peak to
peak current through the resistor.  But Rset on the
board is 3.9K, which is supposed to give a value
for so-called "Iout Full Scale" of 3.878 mA.

I would have thought (just guessing) that peak to
peak output current would be equal to Iout Full
Scale, but it appears to be only half of that.

Can anyone clarify this?

Rick
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