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LMX2820: SysRef Delay vs Temperature

Part Number: LMX2820

Hello,

I have a question about Figure 6-16 from LMX2820 datasheet (SysRef Delays vs Temperature). 

It seems that SysRef delay has non-monotonous relationship vs temperature: 

the maximum delay is for 25 degrees (black curve), but for -40 and +105 degrees delays are less.

Is it true or maybe the curves are garbled?

I am asking because delay variations are large and apparently some calibration required.

Alexander.

  • Alexander,

    I have the raw data and this is what it says, but I think that it is because it is off a cycle.  The output frequency is 8.4 GHz and the SYSREF frequency is 131.25 MHz.

    Note that a signal of 131.25 MHz has a period of 7620 ps.  So we can't tell the difference between a delay of 0, 7620, 15240, and k*7620 ps.

    Now if I add 7620 ps to the yellow curve, then it lines up about where it should be.

    Regards,

    Dea

  • Dean, thanks for your answer. I guess you have your own experimental data because it doesn't fit to Figure 6-16 (the delay of k*7620 ps).

    In any case, thanks for explanation.

    Alexander