Semiconductor device with overcurrent protection circuit
View Patent ↗A semiconductor device 1 includes an output MOS transistor M 2 , a sense MOS transistor M 3 , a voltage conversion circuit 20 that converts a sense current of the sense MOS transistor M 3 into a sense voltage, and control MOS transistor M 10 having a gate and a source which receive the sense voltage therebetween and a drain connected to a gate of the output MOS transistor M 2 . The voltage conversion circuit 20 includes a first MOS transistor M 21 diode-connected and a second MOS transistor M 22 connected in series to the first transistor M 21 . A gate of the second transistor M 22 is connected to a node between a gate control circuit 6 and a resistor R 5 which is connected to the gate of the output MOS transistor M 2 . A variation in threshold voltage caused by characteristic variation of the control MOS transistor M 10 causes a variation in output current limiting value, but the threshold voltage of the first MOS transistor M 21 diode-connected varies similarly, whereby the variation in threshold voltage caused by characteristic variation of the control MOS transistor M 10 is cancelled. As a result, the variation in output current limiting value is suppressed.
1. A semiconductor device, comprising:
an output MOS transistor having a drain connected to a power source terminal, a source connected to an output terminal and a gate receiving a gate control signal from a gate control circuit;
a sense MOS transistor having a gate and a drain which are connected to the gate and the drain of the output MOS transistor, respectively, and a source;
a voltage conversion circuit connected between the source of the sense MOS transistor and the output terminal, and converting a sense current flowing through the sense MOS transistor into a sense voltage; and
a control MOS transistor having a gate and a source which receive the sense voltage therebetween and a drain connected to the gate of the output MOS transistor,
wherein the voltage conversion circuit includes:
a first MOS transistor diode-connected; and
a second MOS transistor, connected in series to the first MOS transistor, and having a gate connected to the gate control circuit.
2. The semiconductor device according to claim 1 , wherein
a threshold voltage of the first MOS transistor has substantially the same characteristic as a threshold voltage of the control MOS transistor.
3. The semiconductor device according to claim 1 , wherein
a drain of the second MOS transistor is connected to the source of the sense MOS transistor, and
a gate and a drain of the first MOS transistor are connected to each other and connected to a source of the second MOS transistor, and a source of the first MOS transistor is connected to the output terminal.
4. The semiconductor device according to claim 1 , wherein
a gate and a drain of the first MOS transistor are connected to each other and connected to the source of the sense MOS transistor, and
a drain of the second MOS transistor is connected to a source of the first MOS transistor, and a source of the second MOS transistor is connected to the output terminal.
5. The semiconductor device according to claim 1 , wherein
the output MOS transistor is an N-channel MOS transistor, and
the gate control circuit comprises a charge pump.
6. The semiconductor device according to claim 1 , wherein
the control MOS transistor and the first MOS transistor are of the same conductivity type.
7. The semiconductor device according to claim 1 , further comprises
a resister connected between the gate control circuit and the gate of the output MOS transistor.
8. The semiconductor device according to claim 7 , wherein
the gate of the second MOS transistor is connected to a node between the gate control circuit and the resistor.