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LMX2595: Lock Frequency tolerance

Michael T Schneider
Expert 3790 points
Part Number: LMX2595

I am looking for the Reference Frequency tolerance for when the LMX2595 would qualify the frequency is within a specified range.

For example if I would like to use 100MHz as my reference clock input. Will the PLL lock bit show locked at a reference input of 101MHz or  even extreme 120MHz?

  • 0
    TI__Guru** 107190 points

    Hi Michael,

    In a PLL loop, the VCO will track the reference clock. If the reference drifts, the VCO will follow. For example, with 100MHz reference clock and the VCO is 10GHz. The "multiplication factor" of the PLL is 100. Now if the ref clock drift to 102MHz, then the VCO frequency, in theory, will be 10.2GHz. This is only possible if the VCO tuning range is over 200MHz. In LMX2595, we have 7 VCO cores. Each VCO core is further divided into over 100 sub-bands. The tuning range of each sub-band is about 100MHz. So in this example, the PLL will unlock because the VCO is not able to deviate for 200MHz without a re-calibration.