Hi Raphael,
Check out this other similar E2E thread: http://e2e.ti.com/support/data_converters/precision_data_converters/f/73/p/300939/1057291.aspx#1057291
The high frequency noise of the DAC1280 and DAC1282 is a product of the delta-sigma modulator architecture. Delta-sigma modulators have a noise-shaping characteristic that pushes noise into the higher frequency ranges.
Best Regards,
Chris