Pre-buffer voltage level shifting circuit and method

Abstract

A pre-buffer voltage level shifting circuit includes a multi-supply voltage level shifting circuit having single gate oxide devices coupled to produce a pre-buffer output signal to an output buffer. The pre-buffer output signal has a level within normal gate voltage operating levels of the single gate oxide devices for each of the least a plurality of supply voltages. In one embodiment, the multi-supply voltage level shifting circuit includes a current mirror coupled to at least one of the first or second power supply voltage and also uses a non-linear device, such as a transistor configured as a diode, which is coupled to the output of current mirror. The non-linear device is coupled to receive a digital input signal from a signal source, such as from a section of core logic. A switching circuit coupled to the non-linear device selectively activates the non-linear device based on a level of the digital input signal. The circuit, in effect, shifts the core logic supply voltage up to provide efficient and safe control of single oxide gate output buffer transistor devices, such as p-channel devices.

Dependencies are inferred from the claim text.