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LMX2582: can't change the VCO output frequency or power

huan wang
Prodigy 10 points
Part Number: LMX2582

    I can power down and read register data from LMX2582.but the VCO output is always -47dBm at 3.5GHz.I can't change the power through writting reg46 and 47. It also didn't lock. 

I only write a few regs at power up,is it necessary to write all the regs at beginning? hopping for answers,thanks.

  • 0
    TI__Genius 11900 points

    Hello Huan,

    It is best practice to program all the registers on the initial power up. "7.5.1 Recommended Initial Power on Programming Sequence"

    When making changes to the PLL the most important thing is to ensure is that you re-calibrate your VCO. "7.5.2 Recommended Sequence for Changing Frequencies"

    The output power seems quite low, how are your output terminations set up, are you using the EVM?

    Are you able to see changes in the register values when you read back after you write whatever registers you are configuring? 

    Thanks,

    Vibhu