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Original question:

SN74LVC245A: Input transition rate

SN74LVC245A: Input Clamp Current and Input current

Sahil Bhat
Prodigy 70 points

Part Number: SN74LVC245A

The datasheet says that the maximum input clamp current shall be -50mA (maximum) but the datasheet also says that these CMOS buffers have very low input current (20us max) due to high impedance at input ports.

Can you please clarify this confusion between clamp current and input current. How can the clamp current be 50mA when the max input current is 20uA. 

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  • 0
    Guru 326430 points

    The inputs have a high impedance only of you stay inside the recommended operating conditions (between 0 V and 5.5 V).

    There is a clamping diode from GND to the input. It's a silicon diode, so no noticeable current will flow for a voltage above −0.5 V. For lower voltages, the device will not be damaged as long as the current through the diode is smaller than 50 mA.