AnsweredAssumed Answered

AD9739 harmonics level

Question asked by serg-ant on Dec 26, 2012
Latest reply on Jan 14, 2013 by danf

Good evening!


I use AD9738 DAC and yesterday I've obtained first results. I've generated sine wave at 950 MHz and was unpleasantly suprised by the level of harmonics. Datasheet says (page 43) HD's should be at more that -60 dB level, but I've got only -40 - -45 dB.


What could be wrong?


Fdac = 2.5 GHz,

Fout = 950 MHz,

HD2 (M2) = 600 MHz, HD3 (M1) = 350 MHz, image is suppressed by LFCN filter and located at (M3) = 1.55 GHz

Iout = 20 mA,

Startup initialization is similar to recommended at page 47.

Normal mode operation. Mu controller, rx controller, sync controller are locked.

DCI_PST_PH0 = 1, DCI_PRE_PH0 = 0.

Output stage configuration includes 91 Ohm load at IOUTP and IOUTN, balun TC1-1-13M, decoupling capacitor with 1 nF value and LFCN-900D+ filter.