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Switch synchronising of multiple LTM4653 devices

Hi all,

I am currently in the process of designing a board that's main function is as a power supply. We have 48V coming in and require 4 individual, 26V, 3A (max) outputs. We have settled on using 4 LTM4653 step down converters with a switch frequency of 1.5MHz.

The question is, What is the best way to sychronise the switching of the supplies to prevent any potential EMI issues? In our current design we are currently using an external 1.5MHz clock as an input to the CLKIN pin on each of the supplies. This means that they should be switching in phase with one another. I believe this will increase the input voltage ripple but will it help prevent cross coupled noise between the supplies?

Any advice or links to relevent app note would be much appreciated.