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SN74LVC1G79: output aumatically sets to high when power on

Gary Zeng
Intellectual 1145 points
Part Number: SN74LVC1G79
Other Parts Discussed in Thread: SN74LVC1G374

Tool/software:

Hi team,

My customer is using SN74LVC1G79 and met issue during the power on.

Magenta channel 4 is the D input signal of the trigger, yellow channel 1 is the 5V power supply, green channel 2 is the clk signal, and blue channel 3 is the output of the trigger; the current phenomenon is that when the D input and clk signal of the trigger are both low, the output of the trigger will follow the 5V power supply voltage, and the duration is 7.44ms.

Q1: Is it normal during the power on and output automatically sets to high. 

Q2: Can SN74LVC1G374 be used for solving this issue? We want to keep OE high when power on and set it to low after power on.

Q3: Do we have relevant device with opposite OEn logic vs SN74LVC1G374?

  • +1
    TI__Intellectual 1490 points

    Hi Gary,

    Gary Zeng said:
    Q1: Is it normal during the power on and output automatically sets to high. 

    This is normal. Please see This FAQ for an explanation.

    Gary Zeng said:
    Q2: Can SN74LVC1G374 be used for solving this issue? We want to keep OE high when power on and set it to low after power on.

    An Output Enable option seems like it may be a good choice for your problem.

    Gary Zeng said:
    Q3: Do we have relevant device with opposite OEn logic vs SN74LVC1G374?

    The OE logic for our devices typically works the same way. Consider tying OE to VCC using a pull-up resistor to ensure a high-Z state during power-on. An alternative might be TPLD. 

    Regards,

    Nikki