INTEGRATED CIRCUIT DEVICE

Poor opening is detected with certainty and reliability with respect to a ground line of an integrated circuit device regardless of the connection state of a load and the operating state of a drive circuit. In an integrated circuit device 10, a drive circuit 30 switches between conduction and interruption of a load current using switch elements 40 and 45. The ground line 31 is grounded via the GND terminal 32 to the common ground provided outside the integrated circuit device 10 and is connected to the drive circuit 30. The ground line 21 is grounded to the common ground via the GND terminal 22 and is connected to the control circuit 20. The diagnostic current supply circuit 90 supplies a predetermined diagnostic current to the ground line 31. The rectifying elements 61 and 62 are connected between the ground line 21 and the ground line 31. The diagnostic circuit 70 measures the potential difference between the ground line 31 and the ground line 21 and compares the potential difference with the predetermined comparison voltage 73 to diagnose the grounding state of the ground line 31.