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LMH0384: 3G-SDI 1080p VIDEO SOURCE DETECTION ISSUE

yeswanth reddy
Prodigy 10 points
Part Number: LMH0384
Other Parts Discussed in Thread: DS25CP104A, LMH0346, LMH0303



We are writing this mail as we are facing video detection issue with 3G-SDI, would like to have support on the same.

The setup as shown in the below block diagram:


  • Input Source: DVD player or Media player
  • Cable Equalizer: LMH0384
  • Cross point switch: DS25CP104A
  • Reclocker: LMH0346
  • Cable Driver: LMH0303
  • BNC cable: 75ohm impedance





Scenario1:Working condition

  • I/P SOURCE :Reliance DVD Player.
  • Setup is able to detect 1080p 50/60Hz

Scenario2:Not working

  • I/P SOURCE :Amkette HD TV Player.
  • Setup is working properly till 1080i 60Hz,
  • With 1080p 50Hz and AEC settings in cable equalizer,able to see detection of video input for 3-4 secs after that it goes blank.
  • Direct connection of the media player with PC Capture card its working properly with all resolutions.

I have attached screenshots of Custom board schematics for reference.

  • 0
    TI__Mastermind 29655 points
    Hi Yeswanth,

    Thanks for your patience as we looked over your schematic. I have a few questions to gain some better understanding:

    1. For the nonworking case, is there a variance of performance when changing between the different BNC inputs? Does it work on one BNC input and not the other?

    2. For the nonworking case, does the LOCK DET pin on the LMH0346 ever trigger, high, or does it remain unlocked? If you enable signal bypass (Tie Reclocker Bypass High on the LMH0346), does signal come out of the output? I want to know if the signal is being affected by an inability to lock on the reclocker side or if the issue is actually coming from the LMH0384.

    3. On the Cable Driver output, I noticed that SDO0 has a 75-ohm pull-down to GND (R140 and R130). Is this a DNP? Since the BNC connector is terminated by a 75-ohm load, keeping R140 and R130 in the schematic will cause a double-termination and decrease signal integrity. Can you double-check this?

    4. Do you have a board layout file or Gerbers for this? The issue could also be related to the high-speed board layout design.

    Regards,

    Michael