• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 19 subscribers
  • Views 327 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMX2594: LMX2594 Low temperature Phase Noise dergade

Masa Katayama
Intellectual 970 points
Part Number: LMX2594

Hi Dean,

My customer met phase noise degradation at low temperature. It was stable across 85C to -30C however ~5dBc/Hz worse at -30C and ~9dBc/Hz at -40C, at 100kHz offset of 13050MHz output.

The figure 16 and 17 shows phase noise variation at -40C in d/s which does not look like this. 

I am sending measured data, loop filter values, registers, simulation data as well to your email separately.

  

Best regards,

Masa

  • 0
    TI__Mastermind 27581 points
    Masa-san,

    The VCO phase noise of the LMX2594 actually improves at lower temperature, not degrades.

    Likley what is happenening is that the VCO gain is changing and this is changing the loop bandwidth of the PLL. This likely is what is effecting your 100 kHz phase noise. I will be looking out for your email.

    Regards,
    Dean
  • 0 in reply to Dean Banerjee
    Intellectual 970 points
    Hi Dean,

    Thank you very much for your advice. You are right. The customer used old version of PLLatinum Sim. It calculated VCO gain 126.4MHz/V which is much lower than recent simulator calculation, should be 178.9MHz/V. This miss-lead that loop bandwith wider and looks not enough VCO noise cut off.

    Best regards,

    Masa