LMX2595: LMX2571 phase coherent switching between two or more frequencies

Hello forum,

we are using a LMX2596 and want to achieve phase coherent switching between  2 frequencies (preferably with one LMX2596).

To test this we have the LMX2596 on an external 100MHz clock signal which is also our phase reference (on an oscilloscope).

We found that the FCAL_EN needs to be off, when it is on a phase slip is observed between the 100MHz output and the 100MHz reference.

Unfortunately when switching the output frequency to ad different value 110MHz for example and then back again (100MHz) a phase slip is observed in comparison to the 100MHz reference (external clock).

The only way it seems is to have multiple LMX2595 and switch the outputs on and off with fixed output frequency to maintain a defined or constant phase relation to a common clock signal.

Is this observation correct? Or is there maybe a solution to this?

Thank you for your help, Klaus

Settings: 100MHz output (with 100MHz external clock/reference)

Comparison of the Phase relation between reference and output signal 100MHz