an input terminal configured to input an input voltage;

an output terminal configured to output a predetermined setting voltage, which is converted from the input voltage;

a step up/down output unit configured to include

a step down switch connected between the input terminal and an input terminal of an inductor,

a step down regulation switch connected between the input terminal of the inductor and a ground terminal,

a step up switch connected between an output terminal of the inductor and the ground terminal, and

a step up regulation switch connected between the output terminal of the inductor and the output terminal;

a step up/down control unit configured to control step up/down switching; and

a mode select terminal configured to receive a mode select signal to selectively set 1) a step up/down switching mode in which step up/down switching is performed and 2) a bypass mode in which the input voltage is directly bypassed to the output terminal without being subjected to step up/down switching, wherein

(A) when the step up/down switching mode is set based on the mode select signal, the step up/down control unit performs step up/down switching to make the output voltage become the setting voltage so as to generate a control signal to turn on/off the step up/down output unit, and the step up/down output unit operates based on the control signal, and

(B) when the bypass mode is set based on the mode select signal, the step up/down control unit generates a control signal to forcibly turn on the step down switch and the step up regulation switch so as to forcibly turn off the step down regulation switch and the step up switch which are connected to the ground terminal, so that the input voltage is bypassed out to the output terminal through the step down switch, the inductor, and the step up regulation switch from the input terminal, and

wherein when the mode select signal changes the operation mode from the bypass mode to the step up/down switching mode, the step up/down control unit is further configured to:

keep each control signal of the step up/down output unit in the bypass mode during a predetermined period to operate the step up/down output unit in the bypass mode;

change the operation mode of a circuit to control the output voltage of the step up/down control unit to be the setting voltage into the step up/down switching mode so as to restore an operation point of the circuit; and

change the operation mode of the each control signal of the step up/down output unit into the step up/down switching mode, to change the operation mode of the entire step up/down switching regulator into the step up/down switching mode.