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Original question:

LMH1297: What is the maximum cable length?

LMH1297: LMH1297 - Is there a minimum cable length ?

John Miller86
Prodigy 120 points

Part Number: LMH1297

I have an LMH1297 transmitting SDI data to an LMH1297 as a receiver. When a short 9 inch cable length is used we get CRC errors at the receiver. When we use a 5 foot cable we get no errors.

So is there a minum cable length ?

  • 0
    TI__Guru**** 193591 points

    Hi,

    If you bypass the cable EQ with the 9-in cable with the command below, do you still see the issue?

    Thanks

    David

  • 0
    Prodigy 120 points

    I still see the issue with the equalizer bypassed.  I've had software give me a register dump for the LMH1297 where SDI_IO+/- take in 3G SDI and comes out on OUT0+/-. It then goes through 10 inches of track to our FPGA.  I noticed in the register dump that our s/w team leaves the the De-Emphasis at its default value of 001'b. Section 3.15.4 of the programming guide implies that there are only 3 valid settings for the register - 000'b, 010'b and 111'b.  Are these the only valid values allowed for De-Emphasis ?   

    Also, I noticed in the register dump for the LMH1297 that they do not configure the Cable Equalizer on the SDI_IO+/- inputs. Do we need to ??   Or,  since it called an Adaptive Cable Equalizer, is no set-up is required ?

    Thanks,

    John Miller