Patent ID: 6157223
Filing Date: 2000-12-05
Classification: H03K

Abstract:
An output buffer coupling a data input and an enable input to an output, the output buffer operable to receive a first voltage from a first power supply and a second voltage from a second power supply, the output buffer comprising:a first output driver having a gate oxide;a first output cascode coupled to the first output driver and to the output, the first output cascode having a gate, the first output cascode operable to protect the gate oxide of the first output driver from voltage changes on the output;a switching circuit coupled to the enable input, to the data input, and to the gate of the first output cascode;a second output driver having a gate oxide;a second output cascode coupled to the second output driver and to the output, the second output cascode having a gate maintained at a substantially constant voltage, the second output cascode operable to protect the gate oxide of the second output driver from voltage changes of the output; anda level shifter coupled to the data input, to the enable input, and to the first output driver, the level shifter comprising a plurality of cascode devices and operable to provide a voltage to switch the first output driver according to the values of the data input and the enable input.