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LMK04610EVM: Differential Output Question

Leonardo Martinez
Prodigy 40 points

Part Number: LMK04610EVM

Tool/software:

Hello team,

I was measuring output (500 MHz) using an oscilloscope and measuring both inverted and non inverted output from channel 3 and I noticed that my outputs weren't in phase. I proceeded with measuring the outputs for different output channels and all the differential output pairs were not in phase with their respective pair. Is this to be expected or is there something that I am missing?

Thank you.

  • +1
    TI__Mastermind 35500 points

    I'm not sure I understand - are you saying the P and N pins of each output are not appropriately 180° phase aligned with each other? Or are you saying that the P pins of each output are not in phase with each other?

    We expect 60-95ps of skew between different differential pairs, with the primary contributors being internal lengths not being equalized, and 40+ stages of CMOS elements in the channel divider circuits with random process variation at each stage. This should also change as a function of temperature, and will not necessarily be consistent between devices due to whole-die process variation. Even outputs within the same channel tend to exhibit 20-30ps of skew.

  • 0 in reply to Derek Payne
    Prodigy 40 points

    Hello Derek,

    Thank you so much for your reply. I meant that the P and N pins of each output are not 180° phase aligned with one another. 

    I am guessing that there is limits to how much we can reduce the skew. So this skew is something to be expected from each differential output pair and also with each output channel. 

    Thank you, this answers my question.