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LMK04828: DCLKoutX_MUX configuration

Todd Rockoff
Intellectual 480 points

Part Number: LMK04828

DCLKoutX_MUX offers several logically equivalent ways to send an unmodified VCO tone to the output of DCLKoutX_MUX:

  1: DCLKoutX_MUX select bypass

  2, 3, and 4: DCLKoutX_MUX select divider; DCLKoutX_DIV = 1; ! DDDLYdX_EN and/or DCLKoutX_DDLY_PD

  5, 6, and 7: DCLKoutX_MUX select divider+HS;  DCLKoutX_DIV = 1; DCLKoutX_HSg_PD; ! DDDLYdX_EN and/or DCLKoutX_DDLY_PD

  8 ... 16 or so, it's a lot. DCLKoutX_MUX select Analog delay ... there are a few ways to disable the analog delays

Is there any reason to choose other than bypass?

When I program f_DCLKoutX = f_CLKin1 in TICS Pro that has been set up for distribution mode, TICS Pro selects option 7 above, selecting everything except the analog delay through DCLKoutX_MUX while disabling everything. 

Please clarify the reason for that choice? (Maybe I'm not using TICS Pro correctly?)

Hopeful thanks --todd

  • 0
    TI__Guru** 122250 points
    Hi Todd,

    I do not quite follow your question.
    DCLKoutx_MUX has four options only (Divider only; Divider+DCC+HS; Bypass; Analog Delay+Divider).
    Maybe your question is related to Table 16, Table 18 of the datasheet?
  • 0 in reply to Noel Fung
    Intellectual 480 points

    Thank you for the prompt reply, Noel.

    DCLKoutX_MUX has 4 inputs, but the circuits upstream may be powered down.

    It seems to me that the correct DCLKoutX_MUX selection for my goal (distribution mode, with f_DCLKoutX = f_CLKin1) would be "Bypass"

    However, TICSPro selects "Divider+DCC+HS" along with ticking DDLY_PD and HSg_PD and setting the divider to 1

    The footnote on table 16 suggests that a divider value of 1 is not valid w/ some combinations of DCLKoutX_MUX and some upstream circuits.

    Q1: Is there any jeopardy from the TICSPro settings?

    Q2: Why doesn't TICS Pro configure DCLKoutX_MUX for bypass, given a scenario such as this that would appear to demand bypass?

    Thanks --todd

  • 0 in reply to Todd Rockoff
    TI__Genius 9920 points
    Hi Todd,
    TICS Pro is not smart as we expected. When you click "Set Distribution", TICS Pro only makes a path from CLKin1 to distribution circuits (VCO_MUX), there is no changes on previous setting about output divider, delay setting, output types etc.

    "Set Distribution" means we use LMK04828's distribution section, do not use PLL1 and PLL2.
    In this distribution section, we still have flexible options , like dividers , delays functions, including a case with same frequency in and out, as your application.

    Divider =1 is not valid for digital delay.
  • 0 in reply to Shawn Han
    Intellectual 480 points

    Goodonya, Shawn.

    Your answer resolves my issue.

    Cheers --todd