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LMX2572: Phase synchronization can not be achieved

Part Number: LMX2572


I would need some help regarding the phase synchronization of multiple LMX2572 boards.

About the system: I have a custom board and a custom program which imports the register file generated by the "TICS Pro" software. After the register map is loaded only the needed registers are modified.

After loading the registers to all boards (3) a phase lock is achieved. The further idea was to phase synchronize all board.

Case 1: Fosc=10 MHz, RFoutA = 500 MHz. Since the Sync category is 2 the boards could be synchronized just with toggling the VCO_PHASE_SYNC_EN. However, this does not work.

The register write order is as following (VCO_PHASE_SYNC_EN=0 at beginning):

N=N'/2, write R34, R36
VCO_PHASE_SYNC_EN = 1, write R0
N=N', write R34, R36
VCO_PHASE_SYNC_EN = 0, write R0


Case 2. Fosc=10 MHz, RFoutA = 2000 MHz. Since the Sync category is 1 the boards should be synchronized already after lock. However, neither this works.

Have I missed something?

Thank you for the support.

best regards