Voltage supply interface circuit

A method of providing a monolithic interface circuit for providing a voltage, from a control circuit supplied by a supply voltage referenced to a reference voltage, to a terminal likely to be at a high voltage with respect to the supply and reference voltages, wherein the high voltage is higher than the supply voltage, the method comprising:

• using a high-voltage N-channel transistor having its gate intended to receive a control signal referenced to the reference voltage and having its source intended to be connected to the reference voltage, wherein the high-voltage N-channel transistor protects the control circuit from receiving the high voltage;
• and
• using a high-voltage PNP transistor having its base connected to the drain of the MOS transistor, having its emitter intended to receive the supply voltage, and having its collector intended to provide a voltage to the terminal likely to initially be at a high voltage, wherein the high-voltage PNP transistor protects the supply voltage from receiving the high voltage.

An interface circuit, comprising:

• a MOS transistor having a control terminal to receive a first signal;
• a bipolar transistor coupled to the MOS transistor, the bipolar transistor providing a supply voltage to an output terminal of the bipolar transistor in response to receiving a second signal from the MOS transistor;
• wherein, when the bipolar transistor is not providing the supply voltage to the output terminal, the control terminal of the MOS transistor is protected from a voltage higher than the supply voltage received at the output terminal of the bipolar transistor.