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SN74LVC1G123: Pulse generator not resetting

Part Number: SN74LVC1G123

Hello, I am trying to create a repeatable pulse output using the bounce free switch circuit shown in the applications document. For now, in testing, I’m making pin 1 go low with a push button switch. Later, this input will be provided by a pulse from a microcontroller digital output. My problem is that the circuit only pulses once after power up, then it stops working. If I power down for a few minutes and then power up again, it works once, then stops working again. Could I have damaged the IC with an ESD to cause this problem, or is there a Stray capacitance somewhere that doesn’t allow the chip to reset?

Thank you,

David

  • Hi David, and welcome to the forums!

    Can you share a schematic of your complete circuit?

    I'd also like to see a scope shot of the input, timing capacitor, and output if possible.

    It's possible for the device to be damaged by ESD, but it's more likely from my experience that there's some issue with the circuit configuration. I don't think I've ever seen a case of ESD damage that resulted in a latching condition like you're describing.

  • Hello Emrys,

    Thank you for the quick reply! I figured out the problem when I started making the schematic to reply to you. For the pullup resistor on the input, labeled Rpu in the applications document, I was using 20 k-ohm and the instructions say to use 100 k-ohm. As soon as I made that change it started working fine. It's good to know that you are there ready to help, should I experience further problems.

    David

  • Hey David,

    I'm glad you figured it out.

    Please come back any time.