Patent ID: 8593203

Claim:
An interface input between a peripheral circuitry and a host circuitry, said interface input comprising: an input circuit adapted to receive input signal levels that are higher than a maximum signal level that the host circuitry electronic components can reliably handle and to level shift said input signal levels to a desired interface signal level; a keeper circuit coupled to said input circuit operable to maintain trigger levels of level shifted signals consistent with said input signal levels, wherein said keeper circuit comprises: a pull up keeper circuit portion operable to pull up an output signal of said interface input to a first predetermined signal level in response to an input signal received at said input circuit and a pull down keeper circuit portion operable to pull down an output signal of said interface input to a second predetermined signal level in response to said input signal received at said input circuit; a first enable circuitry coupled to said pull up keeper circuit portion operable to enable said pull up keeper circuit portion in response to receiving a first enable signal; a second enable circuitry coupled to said pull down keeper circuit portion operable to enable said pull down keeper circuit portion in response to receiving said first enable signal; a Schmitt trigger coupled to said keeper circuit, said Schmitt trigger operable in response to said keeper circuit to provide an output signal of said input circuit at a first predetermined signal level; and a transistor coupled to an of said Schmitt trigger and operable to selectively enable the output of said input circuit.