Electrostatic breakdown protection circuit and capacitance sensor device

A capacitance sensor device, comprising:

• a sensor capacitor of which a capacitance changes according to changes in an environment;
• a first external terminal to which an electrode of the sensor capacitor is externally attached;
• a first electrostatic breakdown protection circuit which is connected to the first external terminal;
• a first capacitance circuit which has a first reference capacitance;
• and
• a determination circuit which includes a first relay terminal and a second relay terminal, supplies a charging current from the first relay terminal to the sensor capacitor via the first electrostatic breakdown protection circuit and the first external terminal, supplies a charging current from the second relay terminal to the first capacitance circuit, and then compares a magnitude of a potential of the first relay terminal with a magnitude of a potential of the second relay terminal to detect the capacitance of the sensor capacitor or detect whether there is a change in the capacitance of the sensor capacitor,
• wherein the first electrostatic breakdown protection circuit includes:
• a first diode of which an anode is connected to the first external terminal,
• a second diode of which a cathode receives a power supply voltage and an anode is connected to a cathode of the first diode,
• a third diode of which a cathode is connected to the first external terminal, and
• a fourth diode of which an anode receives a ground voltage and a cathode is connected to an anode of the third diode.