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SN74LVC1G80: Output stays high does not toggle to low

Barney
Prodigy 210 points
Part Number: SN74LVC1G80

I have a circuit with the following connections to the SN74LVC1G80:

pin 5 is connected to 3.3V

pin 3 is connected to GND

pin 1 (D) is connected to pin 4 (^Q)

pin 2 (CLK) is connected to the output of a debouncer part (MAX6816)

I am monitoring pin 2 and pin 4 on a scope.

Both pin2 and pin4 indicate 3.3V on the scope.  When the switch input to the debouncer is briefly connected to GND, pin 2 drops to 0V and back up to 3.3V but pin 4 remains high.  Pin 4 remains high even with multiple switch events.

Any ideas why pin 4 stays high?

Thanks

  • 0
    TI__Mastermind 24485 points
    Hello John,

    So are you trying to implement the frequency division circuit shown in the datasheet in Figure 5?
    Do you have a scope shot of what you are seeing, the D input, the Q output, and the CLK?
    Is the input to the device a slow rising edge so that there might be a timing issue?

    Please let us know any additional information you may have, and we would be happy to help!

    Best,
    Michael