Rohm Co., Ltd.

Mikiya Doi

Kenichi Nakata

Kazuhiro Murakami

Yosuke Fukumoto

Hiroki Takeuchi

The semiconductor device according to the present invention has an n-channel output transistor wherein an input voltage is impressed on a drain, and a pulsed switching voltage that corresponds to a switching drive of the transistor is brought out from a source; a bootstrap circuit for generating a boost voltage enhanced by a predetermined electric potential above the switching voltage; an internal circuit for receiving a supply of the boost voltage to generate a switching drive signal, and supplying the signal to a gate of the output transistor; an overvoltage protection circuit for monitoring an electric potential difference between the switching voltage and the boost voltage, and generating an overvoltage detection signal; and a switching element for establishing/blocking electrical conduction between the internal circuit and the end impressed with the boost voltage, in accordance with the overvoltage detection signal.

Semiconductor device and switching regulator using the device

An overheat protection circuitof a semiconductor integrated circuit device of the invention has filter means for removing a high frequency component from a power supply voltage Vcc. Specifically, the overheat protection circuithas: a band gap power supply portion BG and resistors Rand Rthat produce a reference voltage Vref; a transistor Nfor temperature detection; resistors Rand Rthat generate, from the power supply voltage Vcc, a control signal Sctrl according to the on/off state of the transistor N; a transistor Pthat is turned on/off according to the control signal Sctrl; and a transistor Nand resistors Rand Rthat generate an overheat protection signal Stsd according to the on/off state of the transistor P. In addition, the overheat protection circuithas, as the filter means, a resistor Rand a capacitor Cthat are respectively connected to the emitter and the collector of the transistor P. This makes it possible to perform a high-accuracy overheat protection operation despite variations in power supply voltage (superimposition of pulse).

Semiconductor integrated circuit device

A step-up/step-down regulator circuit wherein a switch has a terminal connected to an end of an inductor, another terminal grounded, and a control terminal connected to an end of a switch. In this way, performing an open/close control of the switch can indirectly perform an open/close control of the switch, thereby solving the problem that the structure and operation of a switch control circuit will be complicated when the switching between step-up and step-down operation is realized.

Step-up/down regulator circuit and liquid crystal display device incorporating it

A DC/DC converter is supplied such that the desired output setting voltage can be obtained as the load-side output, even when the difference between the power supply voltage and the output setting voltage of the load-side output is large. This DC/DC converter comprises a switching device, a voltage divider, an error amplifier, an oscillator which outputs a oscillation clock, a slope circuit which receives the oscillation clock and outputs a sawtooth waveform voltage having a slope which begins at the leading edge of the oscillation clock, a comparator which compares the sawtooth waveform voltage and the output voltage of the error amplifier, and a logic circuit which is set by the trailing edge of the oscillation clock, and is reset by the output of the comparator.

DC/DC converter

When an output voltage output from a buffer approaches a ground voltage, a MOS transistor turns off, so that clamp for a gate of the MOS transistor is released.

Growing community of inventors

Kyoto, Japan

Mikiya Doi