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OE pull up resister values

John Liu59
Intellectual 2735 points
Part Number: SN74AVC16T245

Dear,

For SN74AVC16T245, in the datasheet, there are below description:

"To ensure the high-impedance state of the outputs during power up or power down, the OE input pin must be tied to VCCA through a pullup resistor and must not be enabled until VCCA and VCCB are fully ramped and stable. The minimum value of the pullup resistor to VCCA is determined by the

current-sinking capability of the driver."

it mentions the min value is related to the current sinking capability fo the driver, so how to choose the right value for the resister value, could you please give an example?

Thanks.

  • 0
    Guru 316690 points

    See the application report Choosing an Appropriate Pull-up/Pull-down Resistor for Open Drain Outputs (SLVA485).

    In practice, there is a very wide range of allowed values, and everybody just uses 10 kΩ.

  • 0
    TI__Guru 62050 points

    John,

    The app note Clemens provided is good reference, however, since the OE pin is not open drain output but an active low CMOS input pin. Hence, it could be directly connected to gnd if the device must always be enabled.

    If another open drain driver is driving the OE pin, you can follow the app note Choosing an Appropriate Pull-up/Pull-down Resistor for Open Drain Outputs (SLVA485).