Method and apparatus for mode selection for high voltage integrated circuits

A method of selecting modes of operation of a power supply control integrated circuit, comprising:

• setting a high voltage terminal, a reference terminal, and a third terminal of the power supply control integrated circuit to a first voltage;
• buffering the voltage at the high voltage terminal to provide an internal voltage to low voltage circuitry of the power supply control integrated circuit, wherein the internal voltage is representative of the voltage at the high voltage terminal, wherein the low voltage circuitry is adapted to withstand a first maximum voltage relative to the reference terminal, 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;
• raising the voltage at the third terminal to a second voltage;
• and
• enabling 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 first threshold voltage.