| 摘要 |
An input/output (I/O) circuit is provided for selectively sinking current from an I/O pin. The I/O circuit includes: an output driver; a well bias circuit coupled to the I/O pin, the output driver, and an internal supply voltage; and a voltage clamping circuit coupled to the I/O pin and the output driver, the voltage clamping circuit selectively sinking current from the I/O pin to a voltage potential other than the internal supply voltage. In a presently preferred embodiment, the voltage clamping circuit includes: a first switch coupled to the I/O pin and to ground potential; a second switch coupled to the first switch and the I/O pin; a third switch coupled to the first switch and the I/O pin; a voltage divider coupled to the third switch; and a resistor coupled to the first switch and the third switch; where the first switch includes an n-channel transistor, the second switch includes an n-channel transistor, and the third switch includes a p-channel transistor and where when the first switch, the second switch and the third switch are ON, current is sunk from the I/O pin to ground potential.
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