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LMX2491: LMX2491 use questions

user4345157
Intellectual 290 points
Part Number: LMX2491
Other Parts Discussed in Thread: LMX2492

We are going to replace the ADF4158 of ADI using the LMX2491 of TI. Today, when drawing Schematic diagram, we find that the FIN pin input of LMX2491 requires -5~5dBm (1.5GHz, -40~60 degree range), our input is -14~-4dBm, and the typical value is -9dBm. May I use it, please? Is there any risk in a later period of large quantities? Now ready to throw the board.

  • 0
    TI__Mastermind 28001 points

    Hi,

    I can NOT formally guarantee this operation at -9 dBm input.  To get a guarantee requires justification from marketing and product engineering and this typically requires NRE or large volume and we typically want some sort of test coverage.

    In my casual opinion, there is a good amount of margin on this sensitivity.  The higher frequency sister part, the LMX2492 shows sensitivity at room temperature to be typically -37 dBc at 1.5 GHz and I would expect the same or better for the LMX2491.  Sensitivity can vary significantly and I would want at least 15 dB margin and you have 23 dB.  All this said, at the end of the day, if it was my design  going into high volume production, I would not press my luck putting -14 dBm when the spec is -5 dBm.

    Regards,

    Den

  • 0 in reply to Dean Banerjee
    Intellectual 290 points

    Hi

        FIN pin input  requires -5~5dBm of LMX2492's Datasheet.

  • 0 in reply to user4345157
    TI__Guru** 107780 points
    Hi,

    Both devices require -5dBm to 5dBm Fin input power, as stated in their datasheets.
    In LMX2492 datasheet, Figure 4, the plot shows that typically, Fin can be as low as -37dBm at 1.5GHz. LMX2491 has similar characteristic. However, we cannot guarantee that every part can reach this sensitivity.