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LMK05028EVM: How to Synchronize the output frequency using 1 PPS input

Jaison K
Prodigy 10 points
Part Number: LMK05028EVM
Other Parts Discussed in Thread: LMK05028, LMK5B12212, LMK5B33414, LMK5B33216

Tool/software:

Hi,

I'm new to working with clocking and timing devices. I’m currently using the LMK05028EVM and trying to configure it so that a output signal(on OUT6) is phase-locked and frequency-locked to a 1 PPS signal connected to REF_IN2 (IN2_P pin).

My goal is to generate a 10 MHz clock output that aligns precisely with the rising edge of the 1 PPS reference.

I have:
- 1 PPS connected to  IN2_P
- TCXO on board
- Desired output = 10 MHz on OUT6, phase-aligned to 1 PPS

Could you please guide me on:
1. Proper DPLL configuration for this setup (should I use DPLL1 or DPLL2?)
2. How to enable and correctly configure Zero Delay Mode (ZDM)
3. Recommended settings in 1-PPS Jitter threshold section

Thanks in advance for your support!

I have attached you my configuration file :

1pps_sync_output.tcs

  • 0
    TI__Intellectual 1160 points

    Hello Jaison,

    For 1 PPS inputs we do not recommend using the LMK05028 DPLL. The part cannot compensate for noise on the input reference which will cause locking issues.

    For using Zero Delay Mode with a 1 PPS input to generate 10MHz outputs I would recommend using the LMK5B12212. Although this device is limited to only one frequency domain because it can only use 1 input reference and 12 output clocks. If more references are needed please use the LMK5B33216 with two references or the LMK5B33414 with 4 references.

    Please let me know if you need any further assistance or need to receive a new EVM board of our other parts.


    Best Regards,
    Kyle Yamabe

  • 0 in reply to Kyle Yamabe
    Prodigy 10 points

    Hi Kyle,

    Thank you for responding .I’ve considered the recommendations provided earlier.

    But I tried modifying my Config file for the LMK05028EVM,while i was testing I found that my Status LEDs

    -GPIO5 Output DPLL1 Holdover Active (High(glows))

    -GPIO6 Output DPLL2 Holdover Active (Blinks at random manner)

    -STATUS0 Output DPLL1 Loss of Lock (Blinks at random manner)

    -STATUS1 Output DPLL2 Loss of Lock (Blinks at random manner)

    I am attaching you the Modified Config file and video for your reference. Could you try this config file to your setup and let me know where i gone wrong?

    1pps_sync_output_v2.tcs

    Thanks,

    Jaison

  • 0 in reply to Jaison K
    TI__Intellectual 1160 points

    Hello Jaison,

    The LMK05028 cannot lock all the time to a 1 PPS input. It will have an issue where it may not always stay locked to the reference. Since you need a 1 PPS input frequency you will need to use a different DPLL device.

    Best Regards,
    Kyle Yamabe