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LMX2595: LMX2595

singam vamshi krishna
Intellectual 775 points
Part Number: LMX2595
Other Parts Discussed in Thread: PLLATINUMSIM-SW

Hello. I have few Queries regarding LMX2595.

1)  It is clear that the output phase noise of LMX2595 mainly depends on how better the phase noise of the reference signal. Other than the reference signal what amount of phase noise do the Phase Frequency Detector, Charge pump, Loop filter, VCO contributes. I mean how much amount do each and individual blocks contribute to phase noise at the output other than the reference input. On what factor do it exactly depends on??

2) As per the data sheet it is clear that the output power is programmable. How is it possible as the pull up loads are fixed (inductors or resistors).

3) What is the stability of LMX2595 Expressed, In terms of Parts Per Million??

Thanks in Advance.

  • 0
    TI__Genius 11900 points

    Hello Singam,

    You can simulate the phase noise of the LMX2595 using the PLLATINUMSIM-SW tool. In general the phase noise depends on the input, PLL characteristics and VCO characteristics. The PLL and VCO characteristics are determined by the capability of the device chosen and is a combination of the factors you mention above. How much each of these blocks contribute can be simulated by the tool, however it cannot be broken down into how much noise the charge pump adds vs the phase detector. You can use the tool to change the loop filter, charge pump, phase detector frequency, etc and see how the phase noise is expected to change.

    The output power settings changes the internal settings of the device, the output power will also vary based on the load at the output. A 50-ohm pull-up or inductor are recommended to be used.

    In general the specifications we validate on our datasheets are the Normalized PLL 1/f noise and the Normalized PLL noise floor. These metrics can be used to simulate the performance of the PLL. The phase noise over an offset frequency range can then be integrated to determine the jitter on the output. We also list jitter measurements on the datasheet.

    In general I would not expect a ppm error, the output will track the input ppm error. Please also see this:

    https://e2e.ti.com/support/clock-and-timing/f/48/p/719422/2654296

    Thanks,

    Vibhu