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Original question:

SN74LVC1T45: SN74LVC1T45 output is too much rising edge noise

SN74LVC1T45: specification for tri-state appears incomplete

Frank Grobler
Prodigy 30 points
Part Number: SN74LVC1T45

Tool/software:

TI experts,

My application using this device requires switching VCCA via a transistor to induce tristate condition.

The specification SCES515M states: The VCC isolation feature is designed so that if either VCC input is at GND, then both ports are in the high-impedance state. Please expand on "...either VCC input is at GND"

Is this a high impedance state (ie. VCC is disconnected) or is there an impedance required to GND eg. a pulldown resistor or is there a minimum current into VCC. I see mention of Ioz in the Electrical Characteristics which appears to be the leakage current in tristate condition but no further mention of VCC conditions for tristate. Or have I missed something.

FrankCA

  • 0
    TI__Guru 51326 points

    Hi Frank,

    Frank Grobler said:
    The specification SCES515M states: The VCC isolation feature is designed so that if either VCC input is at GND, then both ports are in the high-impedance state. Please expand on "...either VCC input is at GND"

    Datasheet implies if VCCA and/or VCCB is at GND or 0 V. 

    Frank Grobler said:
    Is this a high impedance state (ie. VCC is disconnected) or is there an impedance required to GND eg. a pulldown resistor or is there a minimum current into VCC. I see mention of Ioz in the Electrical Characteristics which appears to be the leakage current in tristate condition but no further mention of VCC conditions for tristate. Or have I missed something.

    This is a high impedance state highlighted below for when either Vcc is at GND, thanks.

    Best Regards,

    Michael.