I am using a AD9957 for a transmitter application. Until now I was successfully using the Profile registers to create my required signals. For our next product we want use the QDUC mode. I am driving the 18 bit data inputs using a microcontroller and I think I have all the right settings for CFR1/2/3. When I program the chip using SPI I do get the PLL lock signal high but the output gives a whole bunch of harmonics of 20MHz (my external clock input).
CFR1 - 0x00 01 00 08
CFR2 - 0x00 00 00 60
CFR3 - 0x1A 3F 41 40
I have programmed my Profile 0 as my desired frequency and I select that from the profile pins. Please let me know if you see something wrong with my setup.