This voltage could have a ripple up to 100mV and the DCDC is working at 1.6MHz.
You will have to add a filter to get rid of the ripple noise from the DCDC
converter. Looking at Figure 22 in the datasheet "ripple rejection ratio vs.
frequency", the ADR365 won’t suppress ripple at his frequency of 1.6MHz.
You should consider how much ripple you can tolerate from the DCDC converter
and through the ADR365 and then design the appropriate filter. I highly suggest
that you look in two places for this:
(1) The application section of the DCDC converter to see if they have a filter
(2) Our new Filter Wizard tool