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LMKDB1108: Driving CML

Mitchell Spears
Prodigy 40 points
Part Number: LMKDB1108


Tool/software:

Hi TI Team, 

I would like to use LMKDB1108 because of it's low jitter for non-PCIE (156.25MHz) applications. My receiver is CML instead of LP-HCSL. How would i implement the translation from LP-HCSL to CML or if there is another device you recommend please let me know. 

Thank you, 

Mitchell.

  • 0
    TI__Mastermind 29542 points

    Hello Mitchell, 
    Can I receive the driver specs such as VOD (swing) and VCM? 
    CML signaling can definitely vary as there is no "standard" 


    LMKDB1xxx family has a very wide input spec. 

    As long as your driver meets the input swing and VCM requirements, it will work fine with LMKDB1108. 

    Can you provide the PN of the driver? I can check it out to ensure compatibility with LMKDB1108. 

    Best regards, 

    Vicente 

  • 0 in reply to vicente flores prado
    Prodigy 40 points

    Hi Vincente, I'm actually not concerned about the input the LMKDB1108. I will use a LP-HCSL oscillator. My question is concerning the output to my CML receiver. I want to what the implementation would be to convert from LP-HCSL to CML. For the input oscillator I am look at SiT9501 or SiT9505, and the single ended swing of my CML receiver is 400mVpp. 

  • +1 in reply to Mitchell Spears
    TI__Genius 11640 points

    Hi Mitchell,

    The output swing of the LMKDB1108 is programmable through register R20. The minimum achievable swing is 600mV, so the datasheet for your receiver will be able to tell you whether that is acceptable or a resistive divider network will be required. 

    Ultimately, your input to the CML receiver will need to have a common mode in the range of 1.5V. The circuitry necessary to satisfy that will be AC coupling caps (~0.1uF) followed by a biasing network that will being the common mode of the P and N signals to ~1.5V. See the attached image for reference.

    Thanks,

    Michael