[time-nuts] Power Supply for AD9852 / AD9854
EWKehren at aol.com
EWKehren at aol.com
Sun Mar 16 15:57:43 EDT 2014
You have not said any thing as to what you expect to get out of the DDS
and how important certain parameters are. We recently did a AD 9913 that Tom
tested extensively http://www.leapsecond.com/pages/ad9913/ using a single
supply for the DDS. Some may take exception but it works for us. The AD
9913 is nice for time nuts applications since it allows precise offsets and we
use it in applications like Dual Mixer and what I call the Austron circuit,
a circuit that is a single channel digital mixer with ping pong counter
and yields 1 E-12 in 1 second. Not ready for release yet.
AD 9913 board is attached.
In a message dated 3/16/2014 12:36:48 P.M. Eastern Daylight Time,
time at patoka.org writes:
I would assume that using two voltage regulators will spread the load.
For the AD9851 I'am planning to put external radiator glued on top of
> those parts dissipate a fair amount of heat, and they're not very big.
> If you turn on everything in the 9854 AND run it at 300 MHz clock, it
> draws about 1.2 Amps (@ 3.3V) which is about 4 Watts.. that's a lot of
> power to get out of the part and keep Tj reasonable. Board layout to
> get the heat out is very important. If they get too hot, they start
> to act flaky. You get extra spurs and more importantly, they don't
> respond to the programming properly (e.g. you send the serial stream
> to program frequency X, and instead it programs some different
> "The heat sink of the AD9854ASVZ 80-lead TQFP package must
> be soldered to the PCB. "
> "Adequate dissipation of heat from the AD9854 relies on all
> power and ground pins of the device being soldered directly to
> a copper plane on a PCB. In addition, the thermally enhanced
> package of the AD9854ASVZ has an exposed paddle on the
> bottom of the package that must be soldered to a large copper
> plane, which, for convenience, can be the ground plane."
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