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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