AD9838 DDS power consumption

Document created by analog-archivist Employee on Feb 23, 2016
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Currently protoyping the AD9838 DDS device and require only one IOUT line,
should the other IOUTB line be left open or tied directly to AGND or through
200R? We're looking to minimise power consumption as this is a battery
application.
The datasheet suggests we could run at a DAC output voltage greater than the
compliance value (0.8V) but out with listed specifications, does this mean
running at a higher Iout setting (with the same load value) or must this be set
at a maximum of 4mA and only running with a higher load value? The Iout is
typically 3mA and I believe 4mA [MAX], if we exceed this value (it actually
gives us an improved sensor drive response) but in doing so do we consume more
power and/or risk damaging the device?

 

The power consumption is defined by the reference current which is constant
(not code dependent).

If you need only single ended signal, you can connect IOUT to GND or thru
200kohms resistance (do not leave floating or connected to Vdd) but neither of
these solutions will minimize current consumption.

The part is designed internally to drive a 4mA max current. If you need higher
output voltage you should use higher output impedance but we don’t recommend,
the output gets distorted for Vout > 1.6V.

You may add an external op-amp/transistor to increase current...

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