Output driver circuit

An output driver circuit with an open-drain output, comprising:

• a constant-current circuit which supplies a constant current;
• a constant-current mirror MOS transistor which generates a voltage based on the constant current;
• a selector circuit which separately receives the voltage based on the constant current that is generated by the constant-current mirror MOS transistor and a voltage of a first supply terminal and outputs one of the received voltages according to a signal supplied to an input terminal of the output driver circuit;
• and
• an output MOS transistor having a gate thereof connected to an output terminal of the selector circuit, an open drain output thereof connected to an output terminal of the output driver circuit, and a source thereof connected to the first supply terminal, the output terminal connected to a second supply terminal through an external pull-up resistor,
• wherein the constant-current mirror MOS transistor and the output MOS transistor constitute a current mirror circuit, the selector circuit is between the constant-current mirror MOS transistor and the output MOS transistor, and
• a current flowing between the source and the drain of the output MOS transistor is limited by a voltage based on the constant current.