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-boun...@febo.com [mailto:time-nuts-boun...@febo.com] På vegne af d0ct0r Sendt: 16. marts 2014 05:22 Til: time-nuts@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 > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- WBW, V.P. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
