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Input data format of LMH1218

Kuo Nowal
Expert 2315 points
Other Parts Discussed in Thread: LMH1218

Hi Sir,

Could you tell me input data format of LMH1218?

What kind of data format (BT1120 or YUV422 or other) can receive LMH1218?

  • 0
    TI__Mastermind 29655 points
    Hi Kuo,

    The LMH1218 receives serialized SDI data according to the SMPTE standards listed in the datasheet (ST-2082, ST-2081, SMPTE 424M, 344M, 292M, 259M, DVB-ASI, SFF-8431 (SFP+) and 10GbE Ethernet for SMPTE 2022-5/6).

    You may use an FPGA to serialize the parallel data format (such as BT1120 or YUV422) into a form that is compatible with the SMPTE standards mentioned above.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Expert 2315 points
    Hi Michael,

    Thank you for your support.

    So, If FPGA output is ST-2082 (12G-SDI).
    In this case, can FPGA output connect to LMH1218?

    Regards,
    Kuo
  • 0 in reply to Kuo Nowal
    TI__Mastermind 29655 points
    Hi Kuo,

    Yes, that is correct. The LMH1218 supports data at 12G, 6G, 3G, 1.5G, SD, and 10GbE (10.3125 Gbps).

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Expert 2315 points
    Hi Sir,

    Thank you for your support.
    At last, I want to confirm interface circuit about between FPGA and LMH1218.

    The LMH1218 input is differential end and FPGA output is single end.
    So, IN0- pin of LMH1218 connect to GND via 75R with DC cut.
    Is this correct?
  • 0 in reply to Kuo Nowal
    TI__Mastermind 29655 points

    Hi Kuo,

    This does not sound correct. It seems like the FPGA's output is already a cable driver. Can you provide more information about the FPGA  output that you are trying to interface with our LMH1218?

    The LMH1218 is expected a 100-ohm differential signal at its input. The LMH1218 output will drive a 75-ohm coax cable. Because the LMH1218 is internally terminated on the input and output, there will be impedance discontinuity if you attempt to interface a 75-ohm output from the FPGA to the LMH1218 input.

    Typically, the FPGA will output a 100-ohm differential signal, which is connected through a 4.7uF AC coupling cap to IN0+/-, such as below:

    Only the LMH1218 output OUT0/- should interface to 75-ohm media.

    Regards,

    Michael