Output driver circuit
An output driver circuit provides an overcurrent protection function by a simple circuit configuration. The output driver circuit has a constant-current circuit, a constant-current mirror MOS transistor, and a selector circuit. The constant-current mirror MOS transistor and the output MOS transistor constitute a current mirror circuit. The gate of the output MOS transistor is controlled by a voltage based on a constant current generated by the constant-current mirror MOS transistor, thereby limiting the current flowing between the source and the drain of the output MOS transistor.
1. 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.
2. The output driver circuit according to claim 1 , wherein the current mirror circuit has a fuse configured to adjust a current mirror ratio to adjust a current limit value of the output MOS transistor.
3. The output driver circuit according to claim 1 , wherein the current mirror circuit has a fuse configured to adjust a current value so as to adjust a current limit value of the output MOS transistor.