Semiconductor integrated circuit device and power supply system
A semiconductor integrated circuit device includes a first voltage terminal, a second voltage terminal, an output terminal, a high-side MOSFET connected between the first voltage terminal and the output terminal, a low-side MOSFET connected between the output terminal and the second voltage terminal and having first and second gate electrodes, a drive circuit that complementally switches on and off the high-side MOSFET and low-side MOSFET, and a second gate electrode control circuit that generates a second gate control signal supplied to the second gate electrode of the low-side MOSFET. The second gate electrode control circuit has a voltage generating circuit that supplies a negative voltage negative in polarity relative to a voltage at the source of the low-side MOSFET, to the second gate electrode of the low-side MOSFET.
1. A semiconductor integrated circuit device comprising:
a first voltage terminal supplied with a first voltage;
an output terminal;
a first MOSFET having:
a drain,
a source,
a first input electrode configured to cause a current path to be formed between the source and the drain, and
a second input electrode located closer to the drain than the first input electrode and aligned beside said current path,
the first input electrode partially overlapping with the drain and being insulated from the drain and the second input electrode by an insulating material,
the first MOSFET being connected between the first voltage terminal and the output terminal and electrically connecting the first voltage terminal to the output terminal according to a first input signal supplied to the first input electrode;
a drive circuit connected to the first input electrode of the first MOSFET, the drive circuit generating the first input signal so that the first MOSFET is switched on and off;
a detecting circuit that detects a current flowing through the output terminal to determine whether a value of the current exceeds a given current value; and
a control circuit connected to the detecting circuit and to the second input electrode of the first MOSFET, the control circuit supplying a voltage to the second input electrode of the first MOSFET, the voltage taking different values according to whether a current flowing through the output terminal exceeds the given current value or not.
2. The semiconductor integrated circuit device according to claim 1 , wherein the control circuit supplies:
a positive voltage, positive in voltage value relative to a voltage at the source of the first MOSFET, to the second input electrode of the first MOSFET when a value of a current flowing through the output terminal exceeds the given current value, and
a negative voltage, negative in voltage value relative to the voltage at the source of the first MOSFET, to the second input electrode of the first MOSFET when the value of the current flowing through the output terminal does not exceed the given current value.
3. The semiconductor integrated circuit device according to claim 1 ,
wherein the first MOSFET has a first-conductivity-type first semiconductor region, a second-conductivity-type second semiconductor region over the first semiconductor region, and a first-conductivity-type third semiconductor region over the second semiconductor region, and
wherein the drain of the first MOSFET is composed of the first semiconductor region, the source of the first MOSFET is composed of the third semiconductor region, the first input electrode of the first MOSFET is composed of a first conductive material embedded within the second semiconductor region, and the second input electrode of the first MOSFET is composed of a second conductive material embedded within the first semiconductor region.
4. The semiconductor integrated circuit device according to claim 1 ,
wherein the drive circuit and the control circuit are formed in a first semiconductor chip,
wherein the first MOSFET is formed in a second semiconductor chip different from the first semiconductor chip, and
wherein the first and second semiconductor chips are sealed in one package.
5. The semiconductor integrated circuit device according to claim 1 ,
wherein the second input electrode is disposed such that the voltage supplied to the second input electrode either expands a depletion layer or decreases a resistance in the drain depending on a polarity of the voltage relative to the source.
6. The semiconductor integrated circuit device according to claim 1 ,
wherein the source and the drain are disposed along a first direction,
wherein the first and second input electrodes are spaced from the source and the drain along a second direction perpendicular to the first direction, and
wherein, in a cross-sectional view, the second input electrode is between the drain and the first input electrode along the first direction.
7. The semiconductor integrated circuit device according to claim 6 , wherein the current path is along the first direction.
8. The semiconductor integrated circuit device according to claim 1 , wherein the second input electrode is insulated from the drain by the insulating material and is adjacent to the current path via said insulating material.