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ONET8501T: To find 3GSDI compatible laser driver and TIA

Revati Adur
Prodigy 20 points

Part Number: ONET8501T
Other Parts Discussed in Thread: ONET1130EP, OPA955, LMH13000, LMH0397

We need a laser driver and TIA compatible for 3GSDI pathological signals. What are the strap settings or APC control modifications need to be performed in the circuit for laser driver and TIA to support the transmission and reception of pathological signals

  • 0
    TI__Expert 3580 points

    Hi Revati,

    A device that can do the laser driving and the receive would be the ONET1130EP, with ONET8501T working as the TIA. 

    Something for a discrete TIA could be OPA955. And LMH13000 is a more up-to-date laser driver though I'm not sure if that will have the speeds you need. 

    I'm not familiar with that protocol, any information on the required rise times and pulse widths could help me more in finding the best device and settings.

    Thanks,

    Evan

  • 0 in reply to Evan Kirkbride
    Prodigy 20 points

    Hi Evan,

    I'm using LMH0397 for video signals to differential signals conversion, later for the optical conversion we will use laser driver and SFP, can anyone else please help us with the settings of driver specifically for pathological patterns of 3GSDI protocol SMPTE424M.

  • 0 in reply to Revati Adur
    TI__Expert 3580 points

    Hi Revati,

    Thanks for the information. I would follow the general advice in this thread:  ONET1151L: Tuning the APC when handling pathological SDI Signals 

    Basically you'll have to play with the comp-cap on pin 23 of the ONET1130EP. 10uF seems to be a good starting point, but looks like there has been some success with pathological signals before. 

    Hope this helps.

    Thanks,

    Evan

  • 0 in reply to Evan Kirkbride
    Prodigy 20 points

    Hi Evan,


    Thanks for your suggestion, this resolved our issue for some extent at the transmitter side.
    But at the receiver side, we are unable to get the output SDI signals from TIA. Are there any settings or any specific method to get output pathological signals

  • 0 in reply to Revati Adur
    TI__Expert 3580 points

    Hi Revati,

    What issue exactly are you seeing on the receiving TIA? Are you receiving with the ONET8501T? 

    Some general thoughts is that there isn't any manual gain control, perhaps a VGA or PGA post amp might be required after.

    Also is there any FPGA afterward to decode the signal?

    Thanks,

    Evan

  • 0 in reply to Evan Kirkbride
    Prodigy 20 points

    Hi Evan,

    We have not yet used ONET8501T in our design, but we are currently testing with the lower speed TIA ONET4251PARGTR. 
    At receiver side, it has PD and TIA, then the output of TIA is given to LMH0397. We are getting waveforms at the output of TIA for around 2V but unable to get the final output at the LMH0397. But when tested with other SFP it is working fine. So, we need to know if there are any modifications to be done at TIA.