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LMX2592: Unlock issue

Part Number: LMX2592

Hi Experts,

Good day! I have posted this inquiry to confirm our conclusion with our customer.

We are using LMX2592 as an LO in our product. In the low-temperature halt test (-50°C ambient temperature, board temperature is around -38°C), we found that there is an unlocked issue of LMX2592, and it can be recovered after re-setting registers.  After checking the datasheet, there is a recommended operating condition: -40°ambient temperature.  So my question is whether the issue is under expectation or not.  And can you help to share with us the root cause for this issue, is there any method to improve? 

The unlock issue happens when the temperature is getting down. If I understand correctly, our OSCin=122.88MHz, do you mean that we change the ACAL_CMP_DLY from 25 to 15 when using it at a low temperature? Or we can keep 15 for all the temperatures?

Thank you in advance for your support.

Best regards,
Jonathan Navor
Texas Instruments | Customer Support Center

  • Hi Jonathan,

    Right, beyond -40C, it happens that the VCO may unlock, especially when VCO frequency > 6.5GHz. The latest datasheet has some recommendation to improve this behavior.

    ACAL_CMP_DLY is used during VCO calibration, it should be set according to the state machine clock. See Table7-8 for details. This register does not have temperature dependence.