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LMX2582: fast calibration but sometimes no lock after new batch of LMX2582

Part Number: LMX2582

Dear TI Team

We use the LMX2582 with fast lock time. The registers are configured according the picture in attachment.

During development phase (Eval-Kit) and first prototypes the synthesizer worked all the time very well. Now we have a new PCB Design with a new Batch of LMX2582 (TI 89J P8CR G4). On this PCB, the VCO is sometimes not able to lock during 0.0007 s. After repeated programming (sometimes several times) over SPI the VCO is finally locked.

There is one change more. At the prototypes we used at pin 8 and 9 a 100 nF series capacitor. At the new PCB series, it was changed to 1 nF.

Question: Could it be that due to our register settings the VCO is not able to lock? It is depending on batch quality? Reasons why the LMX2582 cannot lock?

Thank you for fast clearification and your help.

Best regards

Samuel