Power supply circuit having protection circuit against electrostatic discharge stress and semiconductor device having the power supply circuit

A semiconductor device that modulates a logic signal input to a signal input terminal and outputs a demodulated logic signal from a signal output terminal, comprising a power supply circuit configured to supply an output voltage used for driving the semiconductor device, wherein the power supply circuit includes

• a first transistor connected between an input terminal and an output terminal,
• a feedback voltage generation circuit configured to divide the output voltage to generate a feedback voltage,
• a first voltage generation circuit configured to supply a voltage to a first control terminal of the first transistor via a first node based on the feedback voltage and a reference voltage, and
• a protection circuit configured to, when an input voltage increases above a first threshold voltage within a predetermined time, output a voltage that makes the first transistor non-conducting or places the first transistor in a state where the first transistor has a predetermined resistance value, to the first control terminal,
• wherein the protection circuit includes
• a second transistor connected between the input terminal and the first node, and
• a second voltage generation circuit configured to supply a voltage to a second control terminal of the second transistor in accordance with time change of the input voltage, and
• wherein the second voltage generation circuit includes
• a first capacitor connected between the input terminal and a second node,
• a first resistor connected between the second node and a ground terminal,
• a third transistor with a third control terminal connected to the second node, connected between the ground terminal and a third node, and
• a second resistor connected between the input terminal and the third node, and wherein
• the third node is connected to the second control terminal of the second transistor.

A power supply circuit supplying an output voltage between a first terminal and a second terminal, comprising:

• a first transistor connected between a third terminal inputting an input voltage and the first terminal outputting the output voltage;
• an electrostatic protection circuit connected between the third terminal and the second terminal, and configured to electrically conduct between the third terminal and the second terminal when a voltage between the third terminal and the second terminal exceeds a predetermined voltage;
• and
• a protection circuit configured to output a voltage that makes the first transistor non-conducting or places the first transistor in a state where the first transistor has a predetermined resistance value to a first control terminal of the first transistor via a first node, when the input voltage increases above a first threshold voltage within a predetermined time,
• wherein the first threshold voltage is set to be lower than the predetermined voltage,
• wherein the protection circuit includes
• a second transistor connected between the third terminal and the first node, and
• a second voltage generation circuit configured to supply a voltage to a second control terminal of the second transistor in accordance with time change of the input voltage, and
• wherein the second voltage generation circuit includes
• a first capacitor connected between the third terminal and a second node,
• a first resistor connected between the second node and the second terminal,
• a third transistor with a third control terminal connected to the second node, connected between the second terminal and a third node, and
• a second resistor connected between the third terminal and the third node, and wherein
• the third node is connected to the second control terminal of the second transistor.

A power supply circuit supplying an output voltage between a first terminal and a second terminal, comprising:

• a first transistor connected between a third terminal inputting an input voltage and the first terminal outputting the output voltage;
• an electrostatic protection circuit connected between the third terminal and the second terminal, and configured to electrically conduct between the third terminal and the second terminal when a voltage between the third terminal and the second terminal exceeds a predetermined voltage;
• and
• a protection circuit configured to output a voltage that makes the first transistor non-conducting or places the first transistor in a state where the first transistor has a predetermined resistance value to a first control terminal of the first transistor via a first node, when the input voltage increases above a first threshold voltage within a predetermined time,
• wherein the first threshold voltage is set to be lower than the predetermined voltage,
• wherein the protection circuit includes
• a second transistor connected between the third terminal and the first node, and
• a second voltage generation circuit configured to supply a voltage to a second control terminal of the second transistor in accordance with time change of the input voltage, and
• wherein the second voltage generation circuit includes
• a third resistor connected between the third terminal and a fourth node, and
• a second capacitor connected between the fourth node and the second terminal, and wherein
• the fourth node is connected to the second control terminal of the second transistor.