Patent ID: 7193441

Claim:
A high voltage buffer module used in an input/output buffer circuit coupled between a high voltage circuit and a low voltage circuit, the high voltage buffer module being operated between a first supply voltage and its complementary second supply voltage, the high voltage buffer module comprising: a pull-up module, coupled between the first supply voltage and an output node, for outputting the first supply voltage to the output node, in response to an input signal; and a voltage detection circuit, connected to the pull-up module, including: a bias initiating module configured to operate under the first supply voltage and to change a first preliminary bias voltage to a second preliminary bias voltage when the first supply voltage is reduced to a predetermined level, and a level shifting buffer coupled with the bias initiating module and configured to operate under a second supply voltage and to adjust the first preliminary bias voltage to a voltage level no higher than the second supply voltage, wherein the voltage detection circuit is configured to provide the pull-up module with at least one bias voltage selected from a predetermined set of voltage levels.