As long as it meets the minimum voltage swing a sine wave will clock the DDS. However, be aware the slew rate of a sine wave is frequency and amplitude dependent. Therefore, the output phase noise performance of the DDS could suffer due slew rate just like any other receiver input.

As long as it meets the minimum voltage swing a sine wave will clock the DDS. However, be aware the slew rate of a sine wave is frequency and amplitude dependent. Therefore, the output phase noise performance of the DDS could suffer due slew rate just like any other receiver input.