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LMK04832: LMK04832 - Running VCO0 at 2600MHz

Hendrik Lippek1
Prodigy 40 points
Part Number: LMK04832


Hello,

For our design we need to provide 1.3GHz  clock output (and further divider frequencies of 1.3GHz).

Therefore I set up our LMK04832EVM to single loop mode with 130MHz reference input and PLL2 settings to tune VCO0 to 2600MHz.

TicsPro shows the frequency in red because it is 20MHz out of its specified range (max 2580MHz).

In my test setup this seems to run stable. I did not recognised any problems also in longer test series.

Is the specified range of 2440 - 2580MHz a hard limit where problems are known when operating ouside of this range. Or is this just a range where the VCO is qualified and the proper operation can be guaranteed?

Are there any test results of operating the VCO outside this range or known issues that might occur?

Regards,

Hendrik

  • 0
    Prodigy 40 points

    btw. I saw, that the VCO0 of the LMK04832-SP is specified 2440-2600MHz. So my question is if this frequency range can also be applied for VCO0 of LMK04832

  • +1 in reply to Hendrik Lippek1
    TI__Mastermind 34210 points

    Hendrik,

    LMK04832 industrial-grade (i.e. non -SP) is tested to 2580MHz VCO. We can't guarantee the device will stay locked across the full ±125°C variation at 2600MHz VCO, and some of the performance characteristics (particularly phase noise) might be degraded by ~1dB. That said, we do put some margin in on the VCO ranges to ensure we can always hit the stated datasheet ranges, so nearly every device will allow you to lock a 2600MHz VCO0.

    If you do want to try using LMK04832 with 2600MHz VCO0, you may find that some devices lose lock at temperature extremes - it should virtually always be possible to just reprogram the LSBs of the PLL2 N divider and re-calibrate the VCO to re-acquire lock, but it's an extra step that might need to be considered. There's a very small chance that a device from a process corner might be marginal and the VCO will see significantly degraded performance at 2600MHz or may be unable to lock at temperature extremes. I hesitate to put hard numbers on it, because it's not something we've deeply studied; we just suspect it's possible based on test data statistics. If you're not planning to operate at or near 85°C or -40­°C, I wouldn't expect to encounter a device that can't lock at 2600MHz.

    LMK04832-SP has some design tweaks for space-grade behavior and a more involved test program. We designed for 2600MHz, mostly to ensure the phase noise performance remains acceptable and that lock across temperature is maintained at 2600MHz; and we test and screen for 2600MHz on that device.

    Regards,

    Derek Payne

  • 0 in reply to Derek Payne
    Prodigy 40 points

    Hello Derek,

    thanks for your explanation. This gives me a good understanding. We plan to use the LMK04832 in a temperature controlled environment at 23°C. I measured no temperature above 50°C on top of the chip package (on  a load test with all outputs activated). So we are quite far away from the temperature extremes. I will run further tests for the long term stability. But your answer gives me assurance, that the the LMK04832 will work in our environment.

    Regards,

    Hendrik