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LMK00304: about LMK00304 input threshold

Vera Mao
Expert 5065 points
Part Number: LMK00304


hi dear supporting team,

customer use SE input for LMK00304, but they found there is glitches at CMOS input of LMK00304,  so could you pls help on:

1. how big glitch will affect the output performance? (jitter and etc）

2. the input threshold spec only have max and min value for Vih&Vil. what's the min value for Vih and Max value for Vil?

tks a lot!

  • 0
    TI__Genius 16845 points

    Could you elaborate on what glitch the customer observes? Do you have a oscilloscope waveform?

    A1. LMK00304 output jitter will be the input clock jitter plus some additive jitter. If the glitch does not have a significant impact on the jitter integration bandwidth, you will not see an additional effect. I expect the signal shape at the output will be more square if properly terminated.

    A2. You could use the single-ended swing spec (VI_SE) and common-mode voltage (VCM) to calculate VIH and VIL. See table note 8; for f>100MHz, 3.3V LVCMOS clock amplitude is acceptable.

    Kind regards,
    Lane

  • 0 in reply to Lane Boyd
    TI__Expert 5065 points

    hi Lane,

    tks for the reply! the plot is as below: the glitch has exceed 90% of the amplitude, will it potentially affect the judgement of input signal?  so from your comment, if only the signal meet the swing range and Vcm, even if there is glitch inside, it will not be mistook as another edge and affect the output, right?  tks a lot!

  • 0 in reply to Vera Mao
    TI__Genius 16845 points

    I do not anticipate an issue here. The signal has sufficient swing. Assuming the complementary input is biased to the the common-mode level of this single-ended waveform, I would not expect additional edges in the output.

    Kind regards,
    Lane