Semiconductor device and driving system
An output MOS transistor has a drain connected with a power supply and a source connected with an output terminal. The short-circuit MOS transistor has a source connected with the output terminal. The short-circuit MOS transistor is formed in a semiconductor substrate connected with the power supply. A switching device is formed in a semiconductor region which is formed in the semiconductor substrate, and contains a first diffusion layer connected with the gate of the output MOS transistor and a second diffusion layer formed in the semiconductor region and connected with the drain of the short-circuit MOS transistor.
1. A semiconductor device comprising:
an output transistor having a first terminal connected with a power supply and a second terminal connected with an output terminal which is connected with a load;
a drive circuit configured to drive a control terminal of the output transistor in response to a control signal;
a short-circuit MOS transistor having a source connected with the output terminal and configured to operate in response to the control signal;
a first switching device connected between a drain of the short-circuit MOS transistor and the control terminal of the output transistor; and
a control circuit,
wherein the short-circuit MOS transistor is formed on a semiconductor substrate connected with the power supply,
wherein the first switching device comprises:
a first semiconductor region formed in the semiconductor substrate;
a first diffusion layer formed in the first semiconductor region and connected with the control terminal of the output transistor; and
a second diffusion layer formed in the first semiconductor region and connected with the drain of the short-circuit MOS transistor,
wherein the first switching device is turned on or off based on a voltage of the first semiconductor region, and
wherein the control circuit is formed to control the voltage of the first semiconductor region in response to the control signal.
2. The semiconductor device according to claim 1 , wherein the first switching device is formed as a depletion-type N-channel MOS transistor.
3. The semiconductor device according to claim 2 , wherein a conductive type of the first semiconductor region is of a P type,
wherein the conductive type of the first diffusion layer and the second diffusion layer is of an N type,
wherein the first switching device further comprises a gate electrode provided to oppose to a region between the first diffusion layer and the second diffusion layer in the first semiconductor region, and
wherein the gate electrode and the second diffusion layer are connected with the drain of the short-circuit MOS transistor.
4. The semiconductor device according to claim 3 , wherein the drive circuit drives the control terminal of the output transistor when the control signal is in a first level, and stops the drive of the control terminal of the output transistor when the control signal is in a second level,
wherein the short-circuit MOS transistor is turned off when the control signal is in the first level and is turned on when the control signal is in the second level, and
wherein the control circuit controls the voltage of the first semiconductor region to be coincident with that of the output terminal when the control signal is in the first level, and the voltage of the first semiconductor region to be the ground voltage when the control signal is in the second level.
5. The semiconductor device according to claim 3 , wherein the control circuit comprises:
a load resistance connected between the output terminal and a connection node which is connected with the first semiconductor region; and
a second switching device connected between the connection node and the ground terminal and configured to turn on or off in response to the control signal.
6. The semiconductor device according to claim 5 , further comprising:
a diode connected in series with the second switching device between the connection node and the ground terminal to prevent a current from flowing to the connection node from the ground terminal.
7. The semiconductor device according to claim 6 , wherein the diode comprises:
a P-type semiconductor region formed on an insulating layer which is formed on the surface of the semiconductor substrate; and
the N-type semiconductor region formed on the insulating layer and connected with the P-type semiconductor region.
8. The semiconductor device according to claim 1 , wherein the first switching device is formed as a junction FET.
9. The semiconductor device according to claim 8 , wherein the first switching device further comprises:
a second semiconductor region of a P type formed on the semiconductor substrate; and
a third diffusion layer formed on the first semiconductor region,
wherein the first semiconductor region is formed inside the second semiconductor region,
wherein the first semiconductor region is of an N type,
wherein the first diffusion layer and the third diffusion layer are of an N type, and the second diffusion layer is of a P type, and
wherein the control circuit controls the voltage of the third diffusion layer in response to the control signal.
10. The semiconductor device according to claim 1 , wherein the semiconductor substrate comprises:
an N + type substrate connected with the power supply and heavily doped with the N-type impurity; and
an N − type epitaxial layer formed on the N + type substrate, and
wherein the first semiconductor region is formed in the surface section of the N − type epitaxial layer.
11. A semiconductor device comprising:
an output transistor having a first terminal connected with a power supply and a second terminal connected with an output terminal which is connected with a load;
a drive circuit configured to drive a control terminal of the output transistor in response to a control signal;
a short-circuit MOS transistor which has a source connected with the output terminal, and which is an N-channel MOS transistor having a gate supplied with an inversion signal of the control signal;
a switch transistor as a depletion-type N-channel MOS transistor; and
a control circuit,
wherein the short-circuit MOS transistor and the switch transistor are integrated on a semiconductor substrate connected with the power supply,
wherein a gate and a source of the switch transistor are connected with a drain of the short-circuit MOS transistor,
wherein a drain of the switch transistor is connected with the control terminal of the output transistor, and
wherein the control circuit is configured to control a voltage of a back gate of the switch transistor in response to the control signal.
12. The semiconductor device according to claim 11 , wherein the drive circuit drives the control terminal of the output transistor when the control signal is in a first level, and stops the drive of the control terminal of the output transistor when the control signal is in a second level,
wherein the short-circuit MOS transistor is turned off when the control signal is in the first level and is turned on when the control signal is the second level, and
wherein the control circuit controls the voltage of the back gate of the switch transistor to be coincident with that of the output terminal when the control signal is in the first level, and the voltage of the back gate of the switch transistor to be the ground voltage when the control signal is in the second level.
13. The semiconductor device according to claim 12 , wherein the control circuit comprises:
a load resistance connected between the output terminal and a connection node connected with a back gate of the switch transistor; and
a second switching device connected between the connection node and the ground terminal and configured to switch an ON state and an OFF state off in response to the control signal.
14. The semiconductor device according to claim 13 , further comprising:
a diode connected in series with the second switching device between the connection node and the ground terminal to prevent a current from flowing from the ground terminal to the connection node.
15. The semiconductor device according to claim 1 , wherein the output transistor comprises an output MOS transistor,
wherein the first terminal is the drain of the output MOS transistor,
wherein the second terminal is the source of the output MOS transistor,
wherein the control terminal is the gate of the output MOS transistor.
16. The semiconductor device according to claim 1 , wherein the output transistor comprises an IGBT (insulated gate bipolar transistor),
wherein the first terminal is the collector of the IGBT, the second terminal is an emitter of the IGBT, and the control terminal is the gate of the IGBT.
17. The semiconductor device according to claim 11 , wherein the output transistor comprises an output MOS transistor,
wherein the first terminal is the drain of the output MOS transistor,
wherein the second terminal is the source of the output MOS transistor,
wherein the control terminal is the gate of the output MOS transistor.
18. The semiconductor device according to claim 11 , wherein the output transistor comprises an IGBT (insulated gate bipolar transistor),
wherein the first terminal is the collector of the IGBT, the second terminal is an emitter of the IGBT, and the control terminal is the gate of the IGBT.
19. A driving system comprising:
a semiconductor device; and
an inductive load,
wherein the semiconductor device comprises:
an output transistor having a drain connected with a power supply and a source connected with an output terminal which is connected with the inductive load;
a drive circuit configured to drive a control terminal of the output transistor in response to a control signal;
a short-circuit MOS transistor having a source connected with the output terminal, and operating in response to the control signal;
a first switching device connected between the control terminal of the output transistor and the drains of the short-circuit MOS transistor; and
a control circuit,
wherein the short-circuit MOS transistor is integrated on a semiconductor substrate which is connected with the power supply,
wherein the first switching device comprises:
a semiconductor region integrated in the semiconductor substrate;
a first diffusion layer formed in the semiconductor region, and connected with the control terminal of the output transistor; and
a second diffusion layer formed in the semiconductor region and connected with the drain of the short-circuit MOS transistor,
wherein the first switching device is formed to be turned on and off in response to a voltage of the semiconductor region, and
wherein the control circuit is formed to control the voltage of the semiconductor region in response to the control signal.
20. The driving system according to claim 19 , wherein the inductive load includes a DC motor.