AnsweredAssumed Answered

Once again about the single-ended reference clock source for DDS

Question asked by Alexei_Bazlaev on May 29, 2017
Latest reply on Sep 6, 2017 by Alexei_Bazlaev

Is there a need for a transformer (balun) in the schematics of feeding the ref_clk input of the AD9911 DDS? According to the datasheets of many DDS ICs in single-ended mode the complementary reference clock input should be decoupled to AVDD or AGND via a 0.1 μFcapacitor and the following scheme is attached:

If i'm not mistaken the transformer and the 25 Ohm resistors set for matching of the 50 Ohm feed line from the external reference clock source.
But can we exclude the transformer and the 25 Ohm resistors if the reference clock source is set right near the DDS IC and there is no need for matched feed line? Can the scheme be as the following:

Outcomes