Abstract: A semiconductor integrated circuit includes a constant-voltage circuit that outputs a constant voltage and a constant-current circuit. The constant-current circuit includes a first transistor. A voltage input as an input voltage to a first gate electrode of the first transistor is equal to the node voltage at an intermediate node in a connection path between the output of the constant-voltage circuit and an external resistor. A source region of the first transistor is connected to a fixed power supply, and a drain region of the first transistor is connected to the external power supply via a load. In the first transistor, a constant current can be made to flow between the source region and the drain region based on the input voltage. A constant-current drive system in which the semiconductor integrated circuit and the external resistor have been mounted on a circuit board is also constructed.

Abstract: A signal processing device includes an input terminal configured to be input with an input signal that is active high or an input signal that is active low, a switching terminal connectable to a power supply or ground, a selection circuit configured to select and output the input signal that is active high in a case that the switching terminal is connected to the power supply and select and output the input signal that is active low in a case that the switching terminal is connected to the ground.

Abstract: A signal processing device includes an input terminal configured to be input with an input signal that is active high or an input signal that is active low, a switching terminal connectable to a power supply or ground, a selection circuit configured to select and output the input signal that is active high in a case that the switching terminal is connected to the power supply and select and output the input signal that is active low in a case that the switching terminal is connected to the ground.

Abstract: A semiconductor integrated circuit includes a constant-voltage circuit that outputs a constant voltage and a constant-current circuit. The constant-current circuit includes a first transistor. A voltage input as an input voltage to a first gate electrode of the first transistor is equal to the node voltage at an intermediate node in a connection path between the output of the constant-voltage circuit and an external resistor. A source region of the first transistor is connected to a fixed power supply, and a drain region of the first transistor is connected to the external power supply via a load. In the first transistor, a constant current can be made to flow between the source region and the drain region based on the input voltage. A constant-current drive system in which the semiconductor integrated circuit and the external resistor have been mounted on a circuit board is also constructed.

Abstract: An indicator drive circuit includes a current mirror circuit including a first transistor located at a control side and a second transistor located at a controlled side, a current through the current mirror circuit being switched by an external control signal, a current source adapted to feed a control current to the first transistor of the current mirror circuit, and a switching element adapted to be driven by a current through the second transistor of the current mirror circuit and to switch on or off an indicator light source. The current source includes two transistors cascode-connected.

Abstract: An indicator drive circuit includes a current mirror circuit including a first transistor located at a control side and a second transistor located at a controlled side, a current through the current mirror circuit being switched by an external control signal, a current source adapted to feed a control current to the first transistor of the current mirror circuit, and a switching element adapted to be driven by a current through the second transistor of the current mirror circuit and to switch on or off an indicator light source. The current source includes two transistors cascode-connected.

Abstract: A load drive device has a load drive unit including an input system electrically connectable to a control power supply and an output system electrically connectable to a load drive power supply. The load drive unit supplies the electrical load with load drive voltage from the load drive power supply via the output system when the control power supply applies control voltage to the input system. A potential difference detection unit detects a potential difference between the control voltage and the load drive voltage. A potential fixing unit fixes a potential at a control system electrical route, connecting the control power supply and the input system of the load drive unit, to a prohibition level that prohibits the output system of the load drive unit from driving the electrical load when the potential difference detected by the potential difference detection unit exceeds a predetermined threshold value.

Abstract: A load driving device including a semiconductor switch arranged in a current path extending from a power supply to a load. A control circuit controls activation and deactivation of the semiconductor switch. The control circuit deactivates the semiconductor switch when it is determined that overcurrent is flowing through the current path. A current detector detects current that is flowing through the current path. The control circuit determines that overcurrent is flowing when the current detector continuously detects current that is greater than a threshold value over a predetermined detection time. The detection time is set to be shorter than the time from when the current in the current path exceeds the threshold value to when an increase in resistance value of the semiconductor switch resulting from heat generated by the current lowers the current to the threshold value.

Abstract: A load drive control circuit includes a drive circuit for driving a load. A control circuit, connected to the drive circuit by diagnostic lines, provides the drive circuit with a control command that specifies an operation state. The drive circuit drives the load in the operation state specified by the control command, generates a diagnostic output including diagnostic notification signals each having an H level or an L level, and provides the diagnostic notification signals of the diagnostic output to the control circuit. A signal output unit outputs first and second diagnostic outputs respectively in response to the first and second control command from the control circuit. A diagnostic line failure determination unit checks whether the first and second diagnostic outputs are both normal to determine whether the diagnostic lines includes a failure or not.