Abstract: A control terminal is connected to an external resistor, and is connected to a time constant capacitor. A control unit compares a control voltage with a threshold voltage, and switches the function of a semiconductor device according to the comparison results. A charge/discharge circuit charges or discharges the time constant capacitor connected to the control terminal. The semiconductor device uses the voltage at the control terminal, which changes according to the charging operation or the discharging operation performed by the charge/discharge circuit, as a time constant voltage.

Abstract: According to the invention, as an input voltage of a certain step-up unit of a plurality of stages of step-up units, a stepped-up output of a step-up unit in a stage preceding the certain step-up unit is inputted. This makes it possible to increase the level of a voltage stepped up by each step-up unit, and reduce the number of units. Furthermore, according to the invention, when an output voltage of a step-up unit that performs stepping-up operation according to a reference constant current is lower than a reference voltage, a reference constant current is produced; when the output voltage thereof exceeds the reference voltage, the reference constant current is stopped. This makes it possible to provide stable output of an output voltage at a predetermined level, and reduce an inrush current during start-up to a predetermined current level.

Abstract: According to the invention, a charge pump circuit (21) has, as switching means turned on when a capacitor (C1) is charged, transistors (P1 to P3) connected in parallel between one end of the capacitor (C1) and an input terminal (T1). When the capacitor (C1) is charged, a controller (CNT) determines which of the transistors (P1 to P3) to drive based on the results of monitoring of the input and output voltages by first and second detectors (DET1, DET2). Thus, even if the level of the input voltage varies, it is possible to reduce in-rush current at start-up without causing a drop in the output voltage or a loss in efficiency.

Abstract: In addition to an input terminal, an output terminal, a ground terminal, a plurality of external terminals, and a plurality of charge transfer switches, a semiconductor integrated circuit device has a step-up factor switching terminal. Here, the plurality of charge transfer switches each have a common contact connected to corresponding one of the plurality of external terminals and two selection contacts alternatively connected to the common contact, and one of the selection contacts of the plurality of charge transfer switches is connected to the step-up factor switching terminal, and each of the other selection contacts is connected to one of the input terminal, the output terminal, the ground terminal, and the rest of the other selection contacts. With this configuration, it is possible to make the semiconductor integrated circuit device versatile so that it can be used to form charge pump circuits having different step-up factors.