Abstract: Provided is a power supply switching circuit capable of efficiently supplying a desired voltage among a plurality of voltages to a load. In the case of a P-type semiconductor substrate, N-type MOS transistors are provided between a load and an AC adapter and between the load and a battery, and hence no parasitic diode exists between the load and the AC adapter or the battery, resulting in no current path due to the parasitic diode. Thus, when the AC adapter and the battery are connected to the power supply switching circuit, the N-type MOS transistor is turned off, whereby the current path between the battery and the load is cut off completely and the N-type MOS transistor is turned on. Accordingly, the battery cannot supply a voltage to the load while only the AC adapter can supply a voltage to the load.

Abstract: The present invention has an object to provide a switching regulator power supply apparatus that realizes a plurality of light emitting amount outputs without increasing a total number of structural components thereof. A switching regulator power supply apparatus according to the present invention includes a switching type power converting circuit; a current detecting circuit for producing a feedback signal in response to a load current; and an SWR control circuit for driving the power converting circuit. In the switching regulator power supply apparatus, the SWR control circuit is provided with a control signal input terminal and a reference voltage circuit capable of outputting a plurality of reference voltages based upon a control signal inputted to the control signal input terminal.

Abstract: Provided is a power supply switching circuit capable of efficiently supplying a desired voltage among a plurality of voltages to a load. In the case of a P-type semiconductor substrate, N-type MOS transistors are provided between a load and an AC adapter and between the load and a battery, and hence no parasitic diode exists between the load and the AC adapter or the battery, resulting in no current path due to the parasitic diode. Thus, when the AC adapter and the battery are connected to the power supply switching circuit, the N-type MOS transistor is turned off, whereby the current path between the battery and the load is cut off completely and the N-type MOS transistor is turned on. Accordingly, the battery cannot supply a voltage to the load while only the AC adapter can supply a voltage to the load.

Abstract: A semiconductor device has a DC-DC converter control circuit for selectively carrying out a boosting operation and a deboosting operation in accordance with a value of a power supply voltage supplied to the DC-DC converter control circuit and for outputting an activation pulse during a rise of the power supply voltage. The DC-DC converter control circuit has a voltage detection circuit for monitoring the power supply voltage to judge whether the DC-DC converter control circuit carries out the boosting operation or the deboosting operation. A control circuit controls the output of the activation pulse in accordance with an output signal from the voltage detection circuit and stops the output of the activation pulse when the voltage detection circuit judges that the DC-DC converter control circuit carries out the deboosting operation.

Abstract: The present invention has an object to provide a switching regulator power supply apparatus capable of realizing a plurality of light emitting amount outputs without increasing a total number of structural components thereof which may impede a reduction of costs and an area saving effect in various sorts of potable devices which require the plurality of light emitting amount outputs. A switching regulator power supply apparatus according to the present invention includes a switching type power converting circuit, a current detecting circuit for producing a feedback signal in response to a load current; and an SWR control circuit for driving the power converting circuit. In the switching regulator power supply apparatus, the SWR control circuit is provided with a control signal input terminal and a reference voltage circuit capable of outputting a plurality of reference voltages based upon a control signal inputted to the control signal input terminal.

Abstract: A semiconductor memory device has an external terminal receptive of a voltage for switching an operation mode. A protective transistor is connected between the external terminal and a ground. The protective transistor has a drain region and a gate electrode surrounding the drain region. A voltage detection circuit detects a voltage of the external terminal and outputs a switching signal for switching a first operation mode to a second operation mode when a value of the detected voltage is equal to or higher than a preselected voltage value.

Abstract: A power supply detection circuit for monitoring a power supply voltage is provided in a DC-DC converter control circuit constituting a boosting/deboosting automatic change-over switching regulator in order to detect based on the monitored power supply voltage and a desired output voltage value whether an operation of the DC-DC converter control circuit is a boosting operation or a deboosting operation. When it is detected that the operation of the DC-DC converter control circuit is the deboosting operation at a rise of the power supply voltage, the control is carried out so as not to output an activation pulse in accordance with an output signal from the power supply detection circuit.

Abstract: To provide a semiconductor memory device that suppresses a terminal leak current in a test operation mode. The present invention has the following feature. For suppressing the terminal leak current in the operation mode, a layout is adopted in which a polysilicon layer overlaps with an end of a drain, the layer forming a gate electrode of a protective transistor for protecting an IC when being subjected to an electrostatic noise, the protective transistor being connected to an external terminal for the test operation mode. Consequently, a breakdown voltage of an electrostatic breakdown voltage protective transistor is increased.

Abstract: The semiconductor storage device includes: a booster circuit (12) for boosting a power supply voltage (11) supplied to the IC; and a limiter circuit (13) having a function of performing voltage limitation of a high voltage which is a booster circuit output. The limiter circuit 13 selects one voltage value from two values based on whether it is a data recording/erasing time or an evaluation time, to output the one to the memory circuit block 14.

Abstract: The semiconductor storage device includes: a booster circuit (12) for boosting a power supply voltage (11) supplied to the IC; and a limiter circuit (13) having a function of performing voltage limitation of a high voltage which is a booster circuit output. The limiter circuit 13 selects one voltage value from two values based on whether it is a data recording/erasing time or an evaluation time, to output the one to the memory circuit block 14.