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TLC555: Abnormal Operating Problem

Louis Han15
Genius 4680 points
Part Number: TLC555

Hello

I designed the circuit with TLC555 as below image.

I had a problem with output without TRG signal during testing.

Green (U17-3Pin), Purple(U17-2Pin)

What is the cause of the output when there is no TRG signal?

Best regards.

  • 0
    TI__Mastermind 32648 points

    Hi Louis,

    Can you probe the supply line when the extra output pulse occurs. It may be helpful to add an additional 1uF bypass capacitor to your supply.

  • 0 in reply to Katlynne Jones
    Genius 4680 points

    Hi Katlynne

    I'm Sorry for the late feedback.

    .I changed it to 1uF bypass capacitor, but the symptoms are the same.

    I attached a waveform image of the power supply

    Do you have any history of case these problems?

    Should I change the TLC555?

    Best regards

  • 0 in reply to Louis Han15
    TI__Mastermind 32648 points

    Hi Louis,

    Just for clarification, was there an incorrect output during the waveform of the power supply you attached in the last image? I'd like to see what the VCC at the TLC555 looks like at the same time an incorrect output occurs. The TLC555 recommends a 0.1uF and a 1uF capacitor on the supply placed near the timer. This is a problem we see occasionally and it's usually attributed to power supply noise.