Semiconductor device
A semiconductor device containing a terminal, a power supply voltage dropping circuit that generates a constant voltage, a switch circuit to periodically apply a constant voltage to a terminal in response to a first clock, a current-controlled oscillator circuit, and a counter, and in which the power supply voltage dropping circuit supplies a first current to the switch circuit, the current-controlled oscillator circuit generates a second clock whose frequency changes in response to the value of the first current, and the counter counts the number of second clocks within the counting time.
1. A semiconductor device comprising:
a terminal;
a power supply voltage dropping circuit that generates a constant voltage and includes a first transistor that outputs a first current;
a switch circuit that is supplied with the first current and that periodically applies the constant voltage to the terminal in response to a first clock;
a first current-controlled oscillator circuit that generates a second clock;
a first counter that counts the second clock in a counting time; and
a current mirror circuit that includes the first transistor and a second transistor, and the second transistor supplies a second current to the first current-controlled oscillator circuit,
wherein a frequency of the second clock changes in response to a value of the first current and a value of the second current.
2. The semiconductor device according to claim 1 , further comprising:
a first constant current source that supplies a third current to the switch circuit.
3. The semiconductor device according to claim 1 ,
wherein the switch circuit is an inverter circuit.
4. The semiconductor device according to claim 3 , further comprising:
a touch electrode coupled to the terminal,
wherein a value of the first current changes in response to a change in a parasitic capacitance value of the touch electrode coupled to the terminal.
5. The semiconductor device according to claim 4 ,
wherein the change in the parasitic capacitance value of the touch electrode is detected based on a change in the count of the second clock.
6. A semiconductor device comprising:
a terminal;
a power supply voltage dropping circuit that generates a constant voltage;
a switch circuit that periodically applies the constant voltage to the terminal in response to a first clock;
a first current-controlled oscillator circuit; and
a first counter,
wherein the power supply voltage dropping circuit supplies a first current to the switch circuit,
wherein the first current-controlled oscillator circuit generates a second clock whose frequency changes in response to a value of the first current,
wherein the first counter counts the second clock in a counting time,
wherein the semiconductor device further comprises:
a second transistor,
wherein the power supply voltage dropping circuit includes a first transistor that outputs the first current,
wherein a current mirror circuit includes the first transistor and the second transistor, and
wherein the second transistor supplies a second current to the first current-controlled oscillator circuit.
7. The semiconductor device according to claim 6 ,
wherein a frequency of the second clock changes in response to a value of the second current.
8. The semiconductor device according to claim 7 , further comprising:
a first constant current source that supplies a third current to the switch circuit.
9. The semiconductor device according to claim 7 ,
wherein the switch circuit is an inverter circuit.
10. The semiconductor device according to claim 9 ,
wherein the value of the first current changes in response to a change in a parasitic capacitance value of a touch electrode coupled to the terminal.
11. The semiconductor device according to claim 10 ,
wherein the change in the parasitic capacitance value of the touch electrode is detected based on a change in the count of the second clock.
12. A semiconductor device comprising:
a terminal;
a power supply voltage dropping circuit that generates a constant voltage and includes a first transistor that outputs a first current;
a switch circuit that is supplied with the first current and that periodically applies the constant voltage to the terminal in response to a first clock;
a first current-controlled oscillator circuit that generates a second clock;
a first counter that counts the second clock in a counting time;
a current mirror circuit that includes the first transistor and a second transistor, and the second transistor supplies a second current to the first current-controlled oscillator circuit; and
a touch electrode coupled to the terminal,
wherein a frequency of the second clock changes in response to a value of the first current and a value of the second current, and
wherein a value of the first current changes in response to a change in a parasitic capacitance value of the touch electrode coupled to the terminal.
13. The semiconductor device according to claim 12 , further comprising:
a first constant current source that supplies a third current to the switch circuit.
14. The semiconductor device according to claim 12 , further comprising:
wherein the switch circuit is an inverter circuit.