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  • TI Thinks Resolved

LMK04208: LMK04208 CLK LVDS AC COUPLED DIFFERENTIAL TERMINATION

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Replies: 7

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Part Number: LMK04208

Hi Team,

We are connecting LMK04208 CLK  to RFSoC through AC coupled LVDS termination and we are facing issue in differential clock signal.

In AC coupled LVDS with 100 ohms parallel termination (independent of receiver IC) both the P and N waveform are in same phase.

Without 100 ohms termination differential signals (independent of receiver IC) are in different phase.

Please suggest your ideas.

Regards,

Dharma

  • Hello Dharma,

    Can you confirm that your termination matches "Figure 31. LVDS Termination for a Self-Biased Receiver"?

    Can you probe P and N after the 100-ohm termination without the receiver? This will help confirm the issue is not with the LMK04208 and more so how it is interfacing with the RFSoC.

    What is the input specification on the RFSoC? Is it a biases or non-biased LVDS receiver?

    Thanks,

    Vibhu

  • In reply to Vibhu Vanjari:

    Hi Vibhu,

    As per lmk04208 datasheet  in fig 31 we have setup and LVDS output model selector is selected at transmitter end

    When probed at receiver end ( without ibis assignment of receiver) the differential wave form is as shown

    Still we are getting P and N in same phase. Kindly suggest your ideas.

    Regards,

    Dharma

  • In reply to Dharmaraj karupusamy:

    Hello Dharma,

    This seems to be an issue with the IBIS model. The part will not behave the same way.

    Please send me your hyperlynx test bench.

    Have you checked other outputs, and perhaps the LVPECL format? I would think the error would be on them all.

    Thanks,

    Vibhu

  • In reply to Vibhu Vanjari:

    Hi Vibhu,

    Tried attaching the Hyperlynx Line Sim file but it failed to attach. "Contact administrator error is popping up"

    Since we are using LVDS model we have not simulated for LVPCEL model.

    Regards,

    Dharma

  • In reply to Dharmaraj karupusamy:

    Hi Vibhu,

    We are waiting for your response.

    Please let us know if we could send our test setup by any other means.

    Regards,

    Dharma

  • In reply to Dharmaraj karupusamy:

    Hello Dharma,

    I will contact you via email and you can send your simulation over to me. I was going to setup the bench from a blank simulation however, we have limited number of licenses and I haven't been able to test it out yet. Giving me the test bench will fasten up the process.

    If I am able to reproduce your result. I can confirm that the simulation/model for this device is incorrect. The P and N outputs will be 180 degrees out of phase on the actual device.

    Thanks,

    Vibhu

  • In reply to Vibhu Vanjari:

    Hello Dharma,

    I have sent you an email. Let us resolve the issue via email. You can reopen a new ticket if you have related questions by clicking on the "+Ask a related question" button on the top right corner of the webpage.

    Thanks,

    Vibhu

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