Hello initialdream666 ,
What configuration are you using? CLKIN can function either as input data rate clock (PLL enabled) or as a DAC data rate clock (PLL disabled).
In your example, I assume 25MHz is the data rate. the DAC data rate clock would be multiplied by interpolation (4x) = 100MHz. Your 25MHz input data would be sampled by the 100MHz DAC clock. Please refer to page 27 - 32 of the datasheet for more details. Hope this helps.