Sorry, repeat question that I asked in the wrong forum.
Has anyone used the PLLIN/MODE for external synchronization?
I've tried all the options shown on the evaluation board schematic and had no luck.
Other circuits that I've designed recently using the LTC3895 and LTC3858-1, have both worked as described, locking on from a wide range of frequencies.
I just can't get this feature to work in the LTC3891.