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SN74LVC2G125: Reset System

Mark Philip Felipe
Genius 10820 points
Part Number: SN74LVC2G125

Hi Team assisting a customer to check their schematic.

designed a reset system using three tri state buffer SN74LVC2G125 but having an issue with that.

Schematic: /resized-image/__size/640x480/__key/communityserver-discussions-components-files/151/reset-global.JPG

Before they push the push button, the output is pulled low.

When they push on the output is pulled down but when they release the push button, the ouput is still pulled down.

When they release the push button, the output is still at a low state.

Thank you.

-Mark

  • 0
    Guru 316690 points

    I do not understand the description. Was is supposed to say "high" instead of "low" in some place?

    If some of the RESET signals have different values while the button is pressed, the buffers are likely to get damaged.

    What is the purpose of this circuit? What is its desired behaviour?

  • 0 in reply to Clemens Ladisch
    TI__Genius 10820 points

    Hi Clemens, 

    RESET is input and is, right now, not connected to anything. The goal is to provide a way to do a manual reset individually for each component. If i link them directly without the buffer, it won't be possible to reset one individual component that's why I'm using the buffer.

    Thank you.

  • 0 in reply to Mark Philip Felipe
    Guru 316690 points

    CMOS inputs must never be floating. If the three RESET_xxx signals are not connected, you must at least add a pull-up or -down resistor.

    The description is still incomplete. Are the three RESET_xxx signals active low? Where is the output signal (it is not labeled), and what should its value be, depending on the state of all four inputs?