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LMX2492: Power level for Fin

AY
Prodigy 180 points
Part Number: LMX2492

It is stated in the LMX2492 data sheet section 7.6 that the Pfin for single-ended operation should be in the range of -5dBm to +5dBm.

In section 7.8, there is a graph on the typical value of lowest power level of Fin as a function of frequency.

Does it mean that the PLL will still work eventhough the Pfin is below -5dBm? How would this impact the phase noise?

  • 0
    TI__Mastermind 28001 points
    AY,

    The datasheet limit for sensitivity is a very conservative and number we test and ensure. The plot is typical performance. There is no contradiction. Our number is sandbagged because:

    1. I have seen on the order of 5 dB variation on my bench test setup
    2. You would want to stay a good 5-10 dB away from the true sensitivity curve to avoid phase noise degradation and higher spurs.
    3. Due to complications with testing, we put a considerable amount of guardband.
    4. Customers may have matching issues that agitate sensitivity and frankly having more margin mitigates these problems.

    So in summary, the electrical spec number is very conservative and save, as it should be.

    However, typically, you can most likely get this device to operate at far lower levels; I just can't formally guarantee that.

    Regards,
    Dean