Extended voltage range level shifter

An extended voltage range level shifter is provided that includes an input inverter and first and second circuit branches. The input inverter includes thin-gate devices, is coupled to an internal power supply, and is operable to receive internal data and to generate inverted internal data. The first circuit branch includes a p-type, thick-gate transistor that has a source coupled to an external power supply; a first n-type, thick-gate transistor that has a drain coupled to a drain of the p-type transistor and a gate operable to receive a reference voltage that is less than the external power supply and greater than the internal power supply; and a second n-type, thin-gate transistor that has a source coupled to ground, a drain coupled to a source of the first n-type transistor, and a gate operable to receive the internal data. The second circuit branch also includes a p-type, thick-gate transistor that has a source coupled to the external power supply, a drain coupled to a gate of the p-type transistor for the first circuit branch, and a gate coupled to the drain of the p-type transistor for the first circuit branch; a first n-type, thick-gate transistor that has a drain coupled to a drain of the p-type transistor and a gate operable to receive the reference voltage; and a second n-type, thin-gate transistor that has a source coupled to ground, a drain coupled to a source of the first n-type transistor, and a gate operable to receive the inverted internal data.