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TMUX4051-Q1: The typical jitter of the TMUX4051

suy
Expert 1055 points
Part Number: TMUX4051-Q1

Hi team,

   As the title says，what is the typical jitter of the switch’s propagation delay?

  • 0
    Guru 316920 points

    The TMUX4051-Q1 is a passive switch; the propagation delay is caused by the R-C filter formed by RON and CON. ΔRON is about 3 % of RON; there is no information about ΔCON.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 24440 points

    Hello su,

    I agree with what Clemens said.

    In addition, propagation delay is usually load dependent in systems using a mux. The small amount of  prop delay usually introduced by the mux can be model by the r and c value of the mux( like Clemens pointed out). 

    Check out this faq that talks more about this topic.

    Regards

  • 0 in reply to Kameron Hill
    Expert 1055 points
    Hi  Clemens and Kameron,
    We understand that there is a propagation delay. What important to us is the variation of the delay, ie. the jitter of the delay. Does TI have any data on it? And how much does the delay change over temperature?
  • 0 in reply to suy
    Guru 316920 points

    CON depends on the geometry, so it is probably not really affected by temperature. And multiple switches on the same die are probably affected in the same way by temperature changes, so 3 % of the propagation delay is probably a good estimate for the jitter.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 24440 points

    I agree with Clemens on this,

    Temperature doesn't have an effect on prop delay or the variation of that delay called channel skew (jitter of the delay). The faq I attached earlier talks about how to calculate channel skew for ti multiplexers.

    Using that faq I was able to find the channel skew for this device.

    Ex.

    Lets say the supply voltages for this device are vdd=5v and vss=-5v  and the load connected to the device is 1Mohm and 20pf.

    1.If we take the typical values for Ron(60ohm) and con(13pf) at the supply I listed,  add 20 pf to the to the con to represent C load, then multiple them together we get a prop delay of 1980ps 

    2.Next to find the channel skew, we take the typical ΔRON (2ohms) and add that to our original 60 ohm value.

    3.Now we multiply 62 ohm x 33pf    and get = 2046ps

    4. The difference between the new prop delay(2046ps) and old prop delay(1980ps) would give us our channel skew( 66ps) for this system.

    This value is around the 3% variation Clemens said you will see.

    Please let me know if you have any other questions

  • 0 in reply to Kameron Hill
    Expert 1055 points

    Dear Clemens and Kameron，

    I appreciate your help. I think I wasn't clear enough about my question. Here's my problem: first I send a signal to channel 1, I would observe a delay from the output. I call it delay 1. Next I switch to other channels, 2,3,4,etc. Then I switch to channel 1 again and send another signal through the switch. I would get another delay, I call it delay 2. What would be the difference between delay 1 and delay 2? Is this difference a function of temperature? Many thanks!

  • 0 in reply to suy
    TI__Mastermind 24440 points

    Hello Ok,

    I think I understand your exact question now!

    So this change in delay based on Ron flatness is not spec'd in the datasheet but we call it inner channel skew.

    So to get this delay you would use this table of Ron flat values found in the datasheet and do the channel skew calculations found in the Faq.

    Remember to replace the  delta Ron values with the Ron flat values in the datasheet. The difference between the prop delay using 60 ohms and 150 ohms would give you your inter channel skew.

     

    Also the change in ron flat is based on temperature and your assumption is correct.

    Please let me know if you need more assistance!

  • 0 in reply to Kameron Hill
    Expert 1055 points

    Dear Kameron，

    Thanks for your help. 

    I still want to ask, is there specific data for jitter in a short period of time? Does that mean it's negligible?

  • +1 in reply to suy
    TI__Mastermind 24440 points

    Hello suy

    There is no specific data we have for that spec on this part and this jitter should be negligible

    In normal operation your ron flatness should not very that much and to  see it increase to the max 150 value would mean you would need to have the device in max operating temp conditions for a significant amount of time.

    However to illustrate this further. If we use the method i suggested above to find the inner channel skew, we get a value of ( 4950 ps -1980 ps)= 2970 ps or 2.97 ns. This should be negligible in your system. 

    Please let me know if you need any further assistance!

  • 0 in reply to Kameron Hill
    Expert 1055 points

    Dear Kameron，

       I got it，many thanks for you。