[time-nuts] Power Supply for AD9852 / AD9854

d0ct0r time at patoka.org
Sun Mar 16 11:13:48 EDT 2014

Thanks ! Looks like I am on the right track.
I've attached couple of documents which could be useful. I'am going to 
use two separated voltage regulators for VCC/AVDD and DVDD. And use 10 
Ohm / 100Mhz  ferrite board and few capacitors to "separate" VCC and 



On 2014-03-16 07:34, Michael Jensen wrote:
> For inspiration you can look on this design we use for many purposes, 
> the
> design was mainly a beacon exciter but is now also used in many 
> laboratories
> in the developing of laser controlled freq. standards (1x10-18) and 
> also as
> a direct programmable freq. source with milli Herz resolution locked to 
> a 10
> MHz std.
> http://rudius.net/oz2m/ngnb/dds.htm
> In the bottom of the web page is diagrams of both power supply and DDS
> design, the DDS is controlled by an ATMEGA 128A, all is open source.
> // Michael, OZ2ELA
> -----Oprindelig meddelelse-----
> Fra: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] På 
> vegne
> af d0ct0r
> Sendt: 16. marts 2014 05:22
> Til: time-nuts at febo.com
> Emne: Re: [time-nuts] Power Supply for AD9852 / AD9854
> Many thanks indeed for detailed answer ! Yes, I will using Evaluation 
> Board
> for my project.
> Regards,
> V.P.
> On 2014-03-16 00:06, Charles Steinmetz wrote:
>>> By design, DDS "stones" like AD9852 from Analog Devices, required
>>> separated power lines for AVDD, DVDD and VCC.  What will is simple
>>> solution for that ?  I am planing to use following approach: +5V from
>>> linear PS, then three LC filters, then three 3.3V voltage regulators
>>> (Ex.: MC33269T) connected to each filter. Is it good enough ?  May be
>>> its better solution for this ? Or may be that could be simplified to
>>> join AVDD and VCC (AVDD will be connected to VCC via 100 Ohm).
>> Do you have the AD evaluation board, or are you starting with the bare
>> chip?
>> If you really want to know how simple you can make it, why not try it
>> yourself, and see what you need?  You will learn a lot more that way
>> than by asking first every time a question occurs to you.
>> Follow the evaluation board plan and put a 0.1uF (100nF) monolithic
>> ceramic capacitor right at each power input pin of the IC itself
>> (something like 10 capacitors per supply).
>> First, use one 3.3v regulator and feed its output straight to all
>> three circuits, with simply a local bypass cap for each one (plus the
>> per-pin capacitors as noted above).  Run the DDS and see how it
>> performs.
>> Then, see how three separate LC filters perform (each LC fed by the
>> regulated 3.3v supply).
>> Finally, feed the unregulated supply to the "upstream" side of each of
>> the three LC filters, and use a separate 3.3v regulator on the
>> "downstream" side for each supply.
>> In each case, note carefully (at a lot of different output
>> frequencies) the general output noise level and the presence of any
>> spurs and birdies in the output, as well as any logic faults you find
>> (wrong frequency, system hangs up, bus errors, etc.).
>> It might be more instructive to run those steps backwards -- first,
>> see how it works with the most complex (and presumably best) supply,
>> then try the simpler circuits and see what problems crop up.
>> Of course, with either test protocol it is difficult to know whether
>> you have tried every operating state that could cause a problem, so
>> play with it quite a while with each setup and try to use every
>> function and combination.
>> As Chris said, you need to be very careful with your grounds.  These
>> chips are intended to be put on boards with four or more layers.  The
>> AD evaluation board has four layers with a common ground plane for the
>> analog and digital circuitry -- it is possible you could do better
>> with more careful attention to grounding.
>> Best regards,
>> Charles
>> _______________________________________________
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>> and follow the instructions there.
> --
> WBW,
> V.P.
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