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LMK04616: CLKin/OSCin_SE_MODE according to AC/DC-coupling

Theo D
Prodigy 70 points
Part Number: LMK04616

Hello,

When driving the CLKin0 with a singled-ended source with AC-coupling, the datasheet says to set CLKIN0_SE_MODE to 0 so that the component uses the differential buffer mode (P31, 9.3.1.3.2.). When I set it to differential mode (CLKIN0_SE_MODE = 0) the PLL1 never locks. Whereas when I set it to single-ended (CLKIN0_SE_MODE=1) it locks. Can you clarify what the datasheet asks please? Same with OSCin_SE_MODE.

Thank you very much,

Theo

  • 0
    TI__Genius 12560 points

    Hi Theo,

    When you driving CLKinx with sine wave single ended input, it is recommend to use in AC-coupling and would be needed CLKINX_SE_MODE = 1; whereas for LVCMOS or LVTTL single ended input with DC-coupling, CLKINX_SE_MODE should be 1 and for AC-coupling input, CLKINX_SE_MODE should be 0 (set as differential buffer mode).

    Same should be applicable for OSCin input mode also.

    Are you driving CLKin0 input with single ended Sine wave in AC coupling mode? if yes, it should be CLKINX_SE_MODE = 1.

    Thanks!

    Regards,

    Ajeet Pal

  • 0
    Prodigy 70 points

    Hello,

    thanks for your reply.

    I am driving OSCin with LVDS clock and AC-coupling so the datasheet recommends OSCin_SE_MODE = 0 but I need to put OSCin_SE_MODE to 1 if I want the PLL to lock.

    For CLKin : I use LVCMOS with AC-coupling also, the datasheet recommends CLKIN_SE_MODE=0 ; still I need to set it to 1 to get the PLL to lock.

    I am going to try it on the EVM of the LMK04616. But it was my understanding that if I use AC-coupling (which I am on both OSCin and CLKin), I must set the SE_MODE to differential (0) but I never got the PLLs to lock; setting it to 1 enabled the lock flag.

    If you have more info while I test on the EVM, I am all ears,

    Regards,

    Theo

  • 0 in reply to Theo D
    TI__Genius 12560 points

    Hi Theo,

    In the EVM, VCXO at OSCin input is single ended AC coupled input. Hence, it would need an OSCin_SE_MODE = 1, similarly at CLKin0/1 input also AC coupled and if feeding sinewave from sig gen, CLKINx_SE_MODE should be 1.

    Thanks!

    Regards,

    Ajeet Pal