Integrated circuit

An integrated circuit for controlling an ignition system including a coil, the integrated circuit comprising:

• a transistor configured to control a current flowing through the coil, the transistor having an electrode on a ground side thereof and a control electrode;
• a first line coupled to the control electrode of the transistor, the first line being configured to have a first signal and a second signal inputted thereto, a frequency of the second signal being higher than that of the first signal;
• a second line coupled to the electrode of the transistor on the ground side thereof;
• a control circuit configured to control on and off of the transistor, based on a voltage level of the first line, wherein the control circuit is configured to
• turn on the transistor in response to the voltage level of the first line exceeding a first level, and
• turn off the transistor in response to the voltage level of the first line dropping below a second level;
• a Zener diode having a cathode coupled to the first line and an anode coupled to the second line, the Zener diode having such a capacitance that, responsive to the first signal and the second signal being both inputted to the first line, the control circuit controls the on and off of the transistor in response to the first signal irrespective of the second signal;
• and
• a limiter circuit configured to
• detect whether or not a current of the transistor is equal to or larger than a predetermined value, in response to the voltage level of the first line reaching a predetermined level lower than the first level before the transistor is turned on by the control circuit, and
• control the transistor such that the current of the transistor decreases, in response to the current of the transistor becoming equal to or larger than the predetermined value.