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LMH1218: Cascading multiple LMH1218 and jitter

Kevin McNulty
Prodigy 80 points

Part Number: LMH1218
Other Parts Discussed in Thread: LMH1228

Hello,

We are hoping you could help us check into a concern that we have with our new design.  Currently we have a requirement for three SDI outputs and are using three LMH1218 devices in series (see the attached drawing for clarity) to meet this requirement.  One of our concerns is with the jitter on the third output (both on the SDI output and to the subsequent FPGA) as to whether it would exceed the SDI SMPTE specification at a 6G rate or whether this scheme would work at all due to the total jitter throughout the path.

Thanks in advance for the assistance,

Kevin McNultyLMH1218_cascaded_ti.pdf

  • 0
    TI__Guru* 93570 points

    Hi Kevin,

    Thanks for reaching out. I believe there was some email correspondence with TI FAE related to this topic and hope you've seen our responses.

    We have customers using multiple LMH1218 deices in DA application where they cascade multiple devices as you have shown and they do comply with SMPTE alignment jitter requirement. 

    Please note we released a new 12G cable driver - LMH1228 - where 100 ohm output is on the same side as 100 ohm input. This may be better for PCB layout routing. Please take a look at LMH1228 product brief on the web to see if it meets your requirements.

    Regards,,nasser