AD9854 power down

Hi all,

I am using an AD9854 to generate frequencies for a sensor measurement. I find that when I try to power down different sections of the chip when it is not being use that the out put is some severely disfigured mess. The sensor wont be measuring during this phase but I would like if there was a way to power down smoothly to a zero output state.

Is there an app note with this explained maybe?