AD5758 Current ripple improvement

Hi,

for our customer the current ripple due to internall oscillator looks too high (see fig. 55 in the datasheet), however this ripple is not  specified at the diagram.

Are there any possible ways to improve this output? For example, is there a possibility to use an external power supply? If yes, are there any specified conditions for power supply switch on sequence for the VDPC+ and VDPC-?