• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 23 subscribers
  • Views 194 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMK00308: Regard the INPUT CLOCK for LVDS

Filipe Satake
Prodigy 30 points
Part Number: LMK00308
Other Parts Discussed in Thread: LMK03328, LMK6D

Tool/software:

Hi experts,

I have a question regard the INPUT CLOCK of LMK00308.

I am using 100MHz oscillator which will supply the PLL LMK03328.
This finally supply the 2ch CLOCK BUFFER LMK00308.
The LMK00308 will output 8ch x 2 units (16ch) LVDS to DAC Clock input.


I am using LVDS for all configuration.


My Design is in below:



Question: 
1) Is my design correct according to the datasheet of LMK00308 and LMK0332?
2) What can I do to improve my design? Can I use my design without problem?

Best Regards,
Filipe S.

  • 0
    TI__Expert 3595 points

    Hello,

    The clock gen team is out for US holiday. We will return Monday, July 8. Thank you for your patience. 

    Best,

    Cris

  • 0 in reply to Cris Kobierowski
    TI__Genius 16530 points

    Filipe,

    For the LMK03328, no external 100 Ohm resistor is required, due to the way that the device generates the swing for AC-LVDS/AC-CML/AC-LVPECL. See below from the datasheet:

    As such, the requirement is just for the AC-coupling on the output. The output can be connected to an LVDS receiver as follows:

    For the input of the LMK00308, the datasheet states that it can accept AC-coupled LVDS inputs:


    For design improvement, if only one output clock is needed from the oscillator + LMK03328, then the LMK6D can be used instead. Are there any other clocks being generated by the LMK03328 in this use case?
    Thanks,
    Kadeem

  • 0 in reply to Kadeem Samuel
    Prodigy 30 points

    Hi Kadeem,

    Thank you for your reply.
    The LMK00308 accepts the AC-LVDS, but also in the datasheet states:



    In this case, LMK00308 input behavior as non-internal 100Ω termination or internal 100Ω termination included?
    Since there is no information about this in the datasheet, and supposing that it belong to non-internal termination, my circuit should be like in the blobk diamgram below. Is it better or correct according to the datasheet?



     For design improvement, if only one output clock is needed from the oscillator + LMK03328, then the LMK6D can be used instead. Are there any other clocks being generated by the LMK03328 in this use case?
    →     At this moment no. I am only using 100 MHz, and splliting it to 16 ch 100MHz. 
         But in the future it may increase to 180MHz.
        I choose those PLL, and clock buffer becasue they are registered in our company already, and since we do not have time to desgin using a new device, we couldn`t select other ones.

    Best Regards,
    Filipe S.

  • +1 in reply to Filipe Satake
    TI__Expert 8231 points

    Filipe,

    Filipe Satake said:
    Since there is no information about this in the datasheet, and supposing that it belong to non-internal termination, my circuit should be like in the blobk diamgram below. Is it better or correct according to the datasheet?

    Your current design is correct.  You will need the external 100 ohm termination and Ac coupling caps, there is no internal termination on the LMK00308.

    Regards,

    Will

  • 0 in reply to William Pfennigwerth
    Prodigy 30 points

    Thank you, Willian!

    Best regards,
    Filipe S.