Circuit for protecting the input/output stage of a low voltage integrated circuit device from a failure of the internal voltage supply or a difference in the power-up sequencing of supply voltage levels

A circuit comprising:

• protection means for protecting logic circuits within an integrated circuit device from a voltage level external to said integrated circuit device, said protection means and said logic circuits operating at an internal voltage level, said protection means decreasing said external voltage level by a threshold voltage level associated with said protection means, said protection means having associated therewith a terminal voltage difference value, which, when exceeded, causes failure of said protection means;
• pass means for providing a bias voltage to said protection means in the event of a failure of the source of said internal voltage level;
• power supply means coupled to said pass means for providing said internal voltage level to circuits within said integrated circuit device;
• and
• voltage supply means coupled to said pass means for providing a variable voltage to said pass means.

A computer system comprising:

• a plurality of components;
• a bus providing physical and logical connections between said plurality of components;
• and
• an external power supply providing an external voltage to said plurality of components, and wherein one or more components of said plurality of components includes:
• internal logic circuits;
• a protection circuit coupled to an internal power supply and said external power supply, said internal power supply providing an internal voltage, wherein said protection circuit is operable to reduce said external voltage for said internal logic circuits, and has associated therewith a maximum terminal voltage difference, which, if exceeded, causes failure of said protection circuit;
• and
• a pass circuit coupled between said protection circuit and said internal power supply, said internal voltage being lower than said external voltage, and wherein said pass circuit is operable to reduce a terminal voltage difference across said protection circuit in the event of a failure of said internal power supply.