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SN74LVC125A-Q1: The minimum value of the OE pull up resistor and the range of the current-sinking capability

Lei Tao Tao
Prodigy 170 points
Part Number: SN74LVC125A-Q1
Other Parts Discussed in Thread: SN74LVC125A

Hi,

The OE pull up resistor is determined by SN74LVC125A OE port sink current, please share the maximum value of the sink current or the typ pull up resistor value.

When maximum sink current is 10uA, pull up source is 3.3V, so the pull up resistor should not less than 3.3V/10uA=330Kohm，right？

  • 0
    Guru 259530 points

    The maximum value is determined by the leakage current; you do not want the voltage to cross the VIH threshold, so the voltage drop over the resistor should be no more than 0.5 V, so 0.5 V / 10 µA = 50 kΩ.

    The minimum value depends on the drive strength of whatever other device is driving the /OE signal. (But you want a small resistor only if you need to switch very fast.)

    In practice, everybody uses 10 kΩ.