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LMH1297: Using LMH1297 with mixed SDI and MADI formats

Josh Duncan
Prodigy 10 points
Part Number: LMH1297

Tool/software:

Hi there,

This application note (https://www.ti.com/lit/an/snla299/snla299.pdf) details a use case where the LMH1297 can be used as an SDI bidirectional IO as well as a MADI cable driver simultaneously.

The application note provides no details on how this configuration is supported, and which register bits need to be set to support this. It is my understanding that the SDI_OUT cable driver cannot be used as a standalone cable driver when SDI_IO is used in EQ mode, however this is contradicted by two of the four modes detailed in that application note.

Can anyone elaborate further on how this shared SDI/MADI mode works?

Thanks

  • 0
    TI__Expert 5190 points

    Hi Josh,

    When SDI_IO is in EQ mode, the second 75-Ω driver (SDI_OUT) can be used as a loop-through output. It is possible to use SDI_IO as a regular SDI bidirectional IO and SDI_OUT as a MADI output (when SDI_OUT is enabled).

    Best,

    Nick

  • 0 in reply to Nick Peabody
    Prodigy 10 points

    Thanks for the quick reply Nick.

    Where would the MADI signal on the SDI_OUT come from? If SDI_OUT is a loop-through of SDI_IO, would it not just output a copy of the SDI signal at the input? Is it possible to take a MADI signal in on IN+/- and output it via SDI_OUT when SDI_IO is in EQ mode?

    Cheers,

    Josh