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LMX2820: Phase noise data question and Continuous Lock test with EVM

Taketo Sato
Genius 9475 points
Part Number: LMX2820

Hello team,

My customer has questions for LMX2820 below. Could you please support to answer these?

  1. Could you share actual phase noise data around 11GHz? such as figure 3(6GHz) from datasheet.
  2. -236dBc/Hz as typ value of PN_PLL_Flat is specified in electrical characteristics table. Could you let me know measurement condition? or Does PN_PLL_Flat have dependency on f_PD?
    1. Calculating back PN_PLL_Flat from PhaseNoise of figure3 leads to -233dBc/Hz. So customer would like to understand the difference is due to measurement condition or f_PD dependency(electrical table is f_PD=100MHz while figure3 is f_PD=200MHz). If there is a way to improve the 3dB, customer would like to implement.
  3. Is there any way to perform continuous test for Lock testing with using EVM and TICS Pro?

Best regards,

  • 0
    TI__Genius 11900 points

    Hello Taketo-san,

    PLL_FOM does have dependency on phase detector frequency (fpd), when calculating PLL_FOM from a measurement.

    The PLL_FOM decreases 10 x log (fpd) with increasing fpd.

    PLL_flat = PLL_FOM + 20 × log(Fvco/Fpd) + 10 × log(Fpd / 1Hz)

    PLL_FOM = PLL_flat - 20 × log(Fvco/Fpd) - 10 × log(Fpd / 1Hz)

    This might account for your 3 dBc/Hz performance discrepancy. 

    10 x (log 200 - log 100) = 3

    Unfortunately, I do not have the right equipment to take a 11 GHz PN measurement.

    Can you elaborate on what you mean by "continuous test for lock testing"? I am not sure if I understand what this means.

    If you are looking for a way to monitor the device and see if it loses lock over time one option is to monitor the LD pin with a scope. This pin stays high when the device is locked. Alternately you can monitor rb_LD (R74[15:14]) to see if the device loses lock.

    Thanks,

    Vibhu

  • 0 in reply to Vibhu Vanjari
    TI__Genius 9475 points

    Hello Vibhu-san,

    Thank you for your comment.

    I understand PLL_FOM has dependency on phase detector frequency and the 3dB different is come from the fpd difference.

    >Can you elaborate on what you mean by "continuous test for lock testing"? I am not sure if I understand what this means.

    Customer would like to confirm if LMX2820 will lock 100% by performing a lot of calibration such as hundreds thousand times calibration.

    They would like to know if the EVM and GUI supports such the automated lock detection test. Is there any good way?

    >Unfortunately, I do not have the right equipment to take a 11 GHz PN measurement.

    I will contact you offline.

    Best regards,

  • 0 in reply to Taketo Sato
    TI__Genius 9475 points

    Hello Vibhu-san,

    Is there an automated test method using EVM and TICSPro? such as loading text file that lists register values and some wait information and so on.

    Best regards,

  • 0 in reply to Taketo Sato
    TI__Mastermind 27581 points

    0044.TICSPro Automation Example.xlsmTaketo-san

    TICSPro can be automated through labview or Excel.  I have a document for using  LabVIEW (which I cannot support) and also an excel worksheet I created that can be used to call TICSPro.  These can give a good idea of how to automate TICSPro.

    Regards,
    Dean