• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 329 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMH1297: 12G SDI Cable EQ

C BB
Prodigy 10 points
Part Number: LMH1297


Tool/software:

Hello,

We have a problem when used the LMH1297 in EQ mode.

We feed in an SDI video into SDI_IO and output via OUT0 to FPGA, also loopback to SDI_OUT.

FPGA can detect  12G SDI signal of one source equipment,  but if we change another equipment, FPGA can not lock the signal, if the signal is redrived by a video distributor, then next to SDI_IO, FPGA can detect. The SDI-OUT is the same.

We adjust the relative registers, The problem has not been resolved.

Is this a hardware problem and how to optimize? What is your advice?


Best regards

Sandy

  • 0
    TI__Genius 9209 points

    Hi Sandy,

    I would like to request a little more information to better understand your problem.

    My summary of the problem is that the FPGA can detect the 12G SDI signal of one source equipment, but if you change to another source the FPGA cannot lock to the signal. Then if the signal is redrived by a video distributor and then goes to SDI_IO the FGPA can then detect the signal.

    Is the problem not with the source equipment?

    Best Regards,

    Nick

  • 0 in reply to Nick Peabody
    Prodigy 10 points

    Hi Nick,

    Thanks for your reply. The source equipment  has been sold for many years and runs stably, and there is no problem with other devices receiving the 12G SDI signal it outputs.So I think there's a problem with our equipment。

    Best Regards,

    Sandy

  • 0 in reply to C BB
    TI__Genius 9209 points

    Hi Sandy,

    Apologies for the delay in our response. 

    If the LMH1297 locks to the signal you can try adjusting the VOD on the device to see if there is improvement. Beyond that, the best modifications would be to improve the signal to noise characteristics on your transmission line. 

    Best Regards,

    Nick

  • 0 in reply to Nick Peabody
    Prodigy 10 points

    Hi Nick,

    I think VOD has an impact on the output of OUT0, but the SDI_OUT output is also abnormal, so I think the problem is the Cable EQ,
    I have adjusted the VOD and CABLE EQ registers, but there has been no improvement.

    Best Regards,

    Sandy

  • 0 in reply to C BB
    TI__Genius 9209 points

    Hi Sandy,

    The HOST_EQ pin will adjust the VOD and De-emphasis for OUT0+/- and the SDI_VOD pin will adjust the output VOD for the SDI_OUT output. 

    Generally, the auto EQ adaptation for the LMH1297 is a sufficient mechanism for finding the optimal EQ value. However, to see the difference in SDI_OUT when the cable EQ is active and not active you can adjust the OUT_CTRL pin. Setting the OUT_CTRL pin to H will make the SDI_IO cable equalizer bypassed and keep the reclocker enabled. This will allow you to compare the equalized output with the non equalized output to see the effect of the equalization on signal integrity. Sometimes we find that our equalizer is overequalizing the signal input and disabling the equalizer actually has a positive impact on signal integrity.

    Beyond adjusting SDI_VOD and OUT_CTRL, there are certainly changes that you could make to the layout or cabling material to ensure that the LMH1297 is able to lock and that your system works optimally.

    Let me know if you have any further questions.

    Best Regards,

    Nick

  • 0 in reply to Nick Peabody
    TI__Genius 9209 points

    Hi Sandy,

    Closing due to inactivity.

    Best,

    Nick