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SN74LVC1G3157: SN74LVC1G3157DCKR Jitter

user5163805
Prodigy 50 points
Part Number: SN74LVC1G3157
Other Parts Discussed in Thread: TMUX1219, TMUX1248

Tool/software:

I would like to input a crystal oscillator and an external connector clock to SN74LVC1G3157DCKR,
and then input the clock selected by SN74LVC1G3157DCKR to our semiconductor's clock pin.
What is the Jitter value of the SN74LVC1G3157DCKR?
The following are the conditions of use.

Clock frequency: 25 MHz
Supply voltage: 1.8 V
Crystal oscillator phase jitter: 0.32 ps
Operating temperature range: -40degC to +125degC

  • 0
    TI__Mastermind 24440 points

    Hi

    TI Analog multiplexers like the SN74LVC1G3157 do not add significant jitter to applications as they are bidirectional passive devices that are designed to affect the system as little as possible. However if we would like to understand the jitter that multiplexers can add the we can take a look and try to understand the variation in propagation delay of a TI multiplexer.  

    The "jitter" that a TI multiplexer can add to the system is effectively the change in propagation delay the device can have in the application. Because we can look at look at a TI multiplexer effectively as a RC circuit in the analysis and that the on capacitance of a multiplexer stays consistent across testing according to the datasheet, the most important specification that causes a  multiplexer to have jitter is any variation in Delta Ron. However just to reiterate because the SN74LVC1G3157  has low variation in these specs it should be fine in this application and not add any Significant jitter.

    Please let me know if you need any additional help and I am happy to help.

    Regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 50 points

    Thank you for your response.
    I understand that the most important specification that can cause jitter is the variation in deltaRon.
    According to the datasheet for SN74LVC1G3157, the delta Ron is 0.5ohm(Typ).
    Does this mean that there is a 0.5ohm(Typ) variation in Ron?

  • 0 in reply to user5163805
    TI__Mastermind 24440 points

    Hi

    The 0.5ohm(Typ) delta ron spec means that  typically the difference between Ron of the 2 channels of the device will be 0.5 ohms( which means they will have a small difference and effectively this device should provide low jitter)

    The variation in Ron when just looking at one signal path of this device at a time is called Ron flatness 

    If either one of the specs are a concern to you the TMUX1219DCKR could be a option for you as it has better performance in both of the Ron specs

    Please let me know if this helps and clears up your question.

    Regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 50 points

    Thank you for your response regarding the additional question.
    The Jitter we are concerned with is the Jitter when looking at a single signal path. So I understood that Ron flatness is important.
    The following are the conditions of use.
    Clock frequency: 25 MHz
    Supply voltage: 1.8 V
    Crystal oscillator phase jitter: 0.32 ps
    Operating temperature range: -40degC to +125degC
    Therefore, comparing the Ron flatness of the TMUX1219DCKR and SN74LVC1G3157, we understand that the TMUX1219DCKR has better characteristics.
    We will consider whether to adopt TMUX1219DCKR.
    If there is any error in my understanding, please let me know. Thank you in advance.

  • 0 in reply to user5163805
    TI__Mastermind 24440 points

    Hi

    Based of what you just explained i think there are no errors in your understanding as if you are concerned  about propagation delay in a single channel that could also be called "jitter".

    The TMUX1219 is overall the better choice in this application as it low variation in ron specs is good and should provide add very  little  jitter.

    Please let me know if you have any additional questions and I am happy to help.

    Regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 50 points

    Thank you for your answer. Please let me know one last thing.
    In a 2:1 (SPDT) General Purpose Switch with 1.8-V Logic application
    Assuming that Ron flatness at VDD = 1.8 V is the most important parameter, the TMUX1248 appears to be better than the TMUX1219.
    (The TMUX1219 does not include a description of Ron flatness at VDD = 1.8 V, while the TMUX1248 does include a description of Ron flatness at VDD = 1.8 V.)
    Is it correct that the TMUX1248 has better Ron flatness at VDD = 1.8 V than the TMUX1219?

  • +1 in reply to user5163805
    TI__Mastermind 24440 points

    Hi 

    Thank you for pointing this out and looking into this the TMUX1248 would actually be the best option for this application as it has the ron flatness spec at 1.8V and its is p2p(has same pinout) with the SN74LVC1G3157.

    Please let me know if you have any other questions as i can help more if needed.

    Regards,

    Kameron