SCLA061 March   2023 CD74HC4538 , CD74HC4538-Q1 , SN74LV123A , SN74LV123A-Q1

 

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  2.   Design Considerations
  3.   Recommended Parts

Design Considerations

  • The first monostable multivibrator must be retriggerable
  • The output pulse length of the multivibrator must be longer than the period of the keep-alive signal. The pulse length of a multivibrator is T=kRC. The recommended configuration is a 100-kΩ resistor and a 0.1-uF capacitor, for a pulse length of around 10 ms.
  • Either falling-edge or rising-edge trigger configurations can be used for this application. See the datasheet of your selected multivibrator for details.
  • A pull-up or pull-down resistor is required to hold the input at a valid state during reset. The recommended value for this resistor is 10 kΩ.
  • [FAQ] [H] Monostable Multivibrators - Top Questions Answered
  • [FAQ] How does a slow or floating input affect a CMOS device?
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