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Original question:

LMH1208: LMH1208: No output on 12G-SDI (sdi_out1± and sdi_out2± Neither output）

LMH1208: Interface with LMH1219 pcb layout

Murilo Pinheiro
Prodigy 20 points
Part Number: LMH1208
Other Parts Discussed in Thread: LMH1219

Hello,

I am working on a 12G SDI interface in which I am combining LMH1219 and LMH1208 to relay the incoming SDI signal.

My question is regarding the pcb layout, in which I am using pins OUT+ and OUT- from LMH1219 to connect to LMH1208 pins IN0+ and IN0-, respectively. Due to the position of these pins, unless I route them separately, I have to inevitably overlap them in order to connect both IC's. Since this is a layout sensitive design, how is the best way to route such signals?? My initial thought was to partially route one of the signals on the bottom layer using vias but I am not sure how it would affect the impedance.

Thanks in advance,

Murilo

  • 0
    TI__Guru* 93670 points

    Hi Murilo,

    1). Since SDI is polarity in-sensitive, you can connect positive to negative and vice versa between 1219

    output and 1208 input. Please note on LMH1208 you can reverse polarity on any of the output.

    So even if your application is polarity sensitive you can flip the output.

    However, this requires SSMBus access.

    2). On a side note, LMH1208 slew rate has to be set through the pin or SMBus interface.

    LMH1219 does not have an output indication pin to set LMH1208 slew rate. So please be keep this in mind.

    You can set the slew rate through pin or SMBus access.

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 20 points

    Thank you very much Nasser!