Patent ID: 6081152
Filing Date: 2000-06-27
Classification: H03K

Abstract:
An output buffer for driving an output to one of a high output voltage and a low output voltage while limiting voltage across terminals of devices within said output buffer, said output buffer comprising:a pull-up stack of a first plurality of devices, coupled between a high power supply and the output, which turns on when the output is driven to the high output voltage and which turns off when the output is driven to the low output voltage, wherein a voltage difference between the output and the high power supply is distributed across said first plurality of devices when the output is driven to the low output voltage;a pull-down stack of a second plurality of devices, coupled between a low power supply and the output, which turns on when the output is driven to the low output voltage and which turns off when the output is driven to the high output voltage, wherein a voltage difference between the output and the low power supply is distributed across said second plurality of devices when the output is driven to the high output voltage; anda clamping circuit, coupled to the output and to a predetermined node of the first and second plurality of devices, for limiting voltage across terminals of each of the first and second plurality of devices by discharging down said predetermined node when the output is driven to the low output voltage and by charging up said predetermined node when the output is driven to the high output voltage;wherein one of said first plurality of devices of said pull-up stack is coupled to a high voltage input, and wherein one of said second plurality of devices of said pull-down stack is coupled to a low voltage input;and wherein a set of predetermined low voltages is applied on said high voltage input and said low voltage input when said output is driven to said high output voltage, and wherein a set of predetermined high voltages is applied on said high voltage input and said low voltage input when said output is driven to said low output voltage.