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SN74LVC2G17: Buffer output behaviour

Harsh Deosthali
Prodigy 10 points

Part Number: SN74LVC2G17

Hello!

Does this SN74LVC2G17QDCKRQ1 IC have a clamp diode to Vcc on it's output (1Y and 2Y pins)?

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  • 0
    Guru 326490 points

    It has the Ioff feature, so there is no diode. (But while the output is driving high, it is connected directly to VCC.)

  • 0
    Prodigy 10 points

    Thanks for the reply Clemens! 

    Is there a possibility, of voltage leaking into the Vcc rail of the buffer when it's powered off, but I am externally driving the line connected to 2Y pin of the diode via an external UART debugger?

  • 0 in reply to Harsh Deosthali
    Prodigy 10 points

    2Y pin of the buffer* via an external UART debugger.

  • 0 in reply to Harsh Deosthali
    Guru 326490 points

    What diode? There is no diode.

    The Ioff feature prevents exactly this.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    That is understood, what I am facing is, when I am not supplying any power to the buffer IC, but externally driving the line connected to the 2Y (output pin) of the buffer, voltage appears on the Vcc of the buffer.

     

    When I drive the 2Y pin externally via a USB to UART transceiver, 3v3 appears on the 2Y pin of the buffer as expected, but also on the Vcc pin there is a leakage voltage off 2.7V precisely.

    In this case, Vcc = 0V, pin 2Y driven by the USB to UART TX,

    When the UART TX goes 3v3, Vcc goes to 2.7V.

    When the buffer is powered and Vcc is 3v3, this does not happen.

    Only when the buffer is powered off (Vcc = 0V) and I drive the 2Y pin as per the diagram, voltage leaks into the Vcc rail of the buffer.