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Original question:

SN74LVC1G123: SN74LVC1G123 minimum retrigger time calculation

SN74LVC1G123: Retrigger time requirement/calculation

Chetan Karkera
Prodigy 90 points
Part Number: SN74LVC1G123


Tool/software:

Hello 

I would like to know the retriggering time calculations

I am using 10u and 105K external components with the intention of having 1s output pulse width

if i use ,say 100Mhz (50% DC) what will be the required  minimum retriggering duration ?

  • 0
    TI__Genius 11731 points

    Hi Chetan,

    Looking at this graph from the datasheet, you would be below the minimum retriggering duration. Your pulses would be 10 ns apart, and the minimum retriggering duration for this configuration would be over 1 us.

    Best,

    Ian

  • 0 in reply to Ian Graham
    Prodigy 90 points

    Hello Ian,

    I am planning to use frequency divider for this reason, But could you please tell me how to calculate minimum retriggering time so that based on that requirement i can select the divider? 

    Ultimately, it should trigger 1s extended pulse after detecting the last rising edge of the input pulse.

  • +1 in reply to Chetan Karkera
    TI__Genius 11731 points

    Hi Chetan,

    We can only recommend what's in the datasheet, and your capacitor is far outside what we took data for. However, I'd estimate that the minimum retrigger time for your setup is around 1 ms. Note that this is just an estimate and the real number would heavily depend on the system around the monostable. When it comes to situations like this, we typically recommend prototyping with the monostable to find the real value.

    Best,

    Ian

  • 0 in reply to Ian Graham
    Prodigy 90 points

    Hello Ian,

    If in case we are not using retriggering feature, and output pulse width duration tw set for 1sec, what will happen to the output pulse after the 1sec even if the input is continuous ?

    - Once the initial Triggering happens , output goes high till 1sec and then goes low even if the input is 'ON'. Reset only after input goes low for long 

    - Output will go low after 1sec, but again it will goes high after few cycles since input is continuous ?

  • 0 in reply to Chetan Karkera
    TI__Genius 11731 points

    Hi Chetan,

    The inputs are edge sensitive, so if the inputs are continuous, the device will not retrigger after the first event.

    Best,

    Ian