Why is my monostable multivibrator not triggering

Discussion in 'General Electronics Chat' started by Rock Slate, Jul 22, 2015.

  1. Rock Slate

    Thread Starter New Member

    Jul 22, 2015
    27
    1
    Hi guys,

    I am using the LT6993 from linear. I have attached the spice file in ltspice. The problem is that the 2 successive pulses on the rigger input are not triggering the multivibrator twice. The minimum time between them according to the datasheet http://cds.linear.com/docs/en/datasheet/69931234fb.pdf is 10ns

    Could anyone help me out?
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi RS,
    Running your asc file suggests that neither trigger is having an effect.??
    E

    EDIT:
    The 1st trigger pulse is occurring before the set up time.?
     
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    Last edited: Jul 22, 2015
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  3. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,220
    Yes. You apparently misunderstand the meaning of "retriggerable".
    Being a retriggerable monostable does not mean each trigger causes a separate output pulse.
    It means the pulse period is extended after each pulse that occurs before the one-shot time-out, which is what it is doing.
    The output pulse width will be one monostable period beyond the last input pulse.

    Note: Why did you use PWL to generate the trigger pulses? Using the Pulse function is much easier.
     
    Last edited: Jul 22, 2015
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  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    Do not forget that Trigger Propagation Delay is 17ns also Minimum Recognized TRIG Pulse Width is 5ns.
    And you will not see two output pulse if time between trigger pulses smaller than the output pulse.
    See this example and notice that the output pulse is now longer then 1μs because of a second trigger pulse at 1.5μs
     
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  5. Rock Slate

    Thread Starter New Member

    Jul 22, 2015
    27
    1
    Thanks guys. I understand now.
     
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