Patent ID: 7385312

Claim:
A method of setting a mode of operation of a power supply control integrated circuit, comprising: buffering a first voltage at a high voltage terminal of the power supply control integrated circuit to provide an internal voltage to low voltage circuitry of the power supply control integrated circuit, wherein the internal voltage is responsive to the first voltage, wherein the low voltage circuitry is adapted to withstand a first maximum voltage relative to a reference terminal of the power supply control integrated circuit, wherein the high voltage terminal is adapted to withstand a second maximum voltage relative to the reference terminal, wherein the second maximum voltage is substantially greater than the first maximum voltage; setting a normal mode of operation of the power supply control integrated circuit with the low voltage circuitry if the internal voltage is above a first threshold voltage; setting an alternative mode of operation of the power supply control integrated circuit with the low voltage circuitry in response to detecting that the internal voltage is below a second threshold voltage; and switching a power switch during the normal mode of operation of the power supply control integrated circuit, wherein the power switch is coupled between the high voltage terminal and the reference terminal of the power supply control integrated circuit.