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LMK04828: LVDS output termination for oscin of lmx2694

Yoonsun Kim
Expert 1860 points
Part Number: LMK04828

Hi,

The CLKout of lmk04828 on my board is provided to lmx2694 on another board  as a reference clock.

The output format of CLKout is LVDS and AC-coupled.

There are two cases of LVDS termination on pag 105 - 106 on datasheet of lmk04828. I am confused which case should be applied on my schematic for lmx2694.

Attached file is a schematic of lmx2694.

Do I need to place 560 ohm between lmk04828 and AC-coupling capacitor on my board or to change AC-coupling capacitor to 0 ohm resistor so DC-coupled clock to lmx2694?

Regards,

YS Kim

  • 0
    TI__Genius 10995 points

    Hello YS,

    After looking at both data sheets, it looks like the figure from page 105 (shown below) should be the one for you to use for this setup. You should only use a 560 Ω resistor in between the differential pairs if the LMX2694 had a 100 Ω resistor inside, which I don't believe it does.

    I will get back to you tomorrow double checking my above recommendation is correct.

    Best,

    Andrea

  • +1 in reply to Andrea Vallenilla
    TI__Genius 10995 points

    Hello YS,

    Just double checked with my team, how far away is the LMK04828 to the LMX2694? If they are significantly further apart (i.e in different boards or separated by a trace > 7-8 cm), then you do want to include the 560-Ω next to the LMK04828, the capacitors from Figure 31 below, near the LMX2694, and then also include the 100-Ω and two capacitors from Figure 30 close to the LMX2694.

    Hope this helps!

    Good luck,

    Andrea