Seiko Instruments Inc

Takashi Imura

Takao Nakashimo

Masakazu Sugiura

Atsushi Igarashi

Yuji Kobayashi

Yotaro Nihei

Akihito Yahagi

Kaoru Sakaguchi

Teruo Suzuki

Hideo Yoshino

Manabu Fujimura

Tadashi Kurozo

Masahiro Mitani

Provided is a voltage regulator capable of accurately adjusting a tail current of a differential amplifier circuit without adding a test terminal. The voltage regulator includes: a constant current circuit for causing the tail current of the differential amplifier circuit to flow; a protection circuit; a current output circuit for outputting a current of the constant current circuit to a test terminal for measuring characteristics of the protection circuit; a switch circuit for stopping a function of the protection circuit; and a fuse provided between the test terminal and the current output circuit.

Method of measuring characteristics of a protection circuit for a linear voltage regulator

Provided is a voltage regulator including an overcurrent protection circuit, which does not need a test circuit. The voltage regulator has a configuration in which a reference voltage circuit includes an element that determines a reference voltage and an overcurrent protection circuit includes an element that determines a maximum output current, the element of the reference voltage circuit and the element of the overcurrent protection circuit having the same characteristics. Accordingly, there is a correlation between an output voltage before trimming and the maximum output current for overcurrent protection. Thus, a maximum output current before trimming can be estimated without performing evaluation by a test circuit.

Voltage regulator

Provided is a voltage regulator having improved transient response characteristics even when a load current is switched from a light load to a heavy load. The voltage regulator includes, to a gate of a detection transistor constituting an output current detection circuit: a resistive element for interrupting the gate of the detection transistor from an output terminal of a differential amplifier circuit in an AC manner; and a capacitive element connected to an output terminal of the voltage regulator in an AC manner.

Provided is a voltage regulator including a soft-start circuit having a small area and capable of suppressing an inrush current by causing a reference voltage circuit to rise gently with time. In the soft-start circuit, a capacitor is connected to an output of a reference voltage circuit driven by a constant current of a constant current circuit, and hence the soft-start circuit can raise a reference voltage gently to prevent an inrush current with a small area. After the end of a soft-start period, the constant current circuit is disconnected, and the reference voltage circuit is driven by a power source. Thus, the operation becomes stable.

Provided is a voltage regulator capable of reducing an influence of an offset to obtain an accurate output voltage. The voltage regulator includes: a first stage amplifier for amplifying and outputting a difference between a reference voltage and a divided voltage obtained by dividing a voltage output by an output transistor, to thereby control a gate of the output transistor; and a cascode amplifier circuit, in which the first stage amplifier includes: a first high breakdown voltage NMOS transistor as an input transistor; and an NMOS transistor as a tail current source, and in which the cascode amplifier circuit includes a second high breakdown voltage NMOS transistor as a cascode transistor.

Multi-stage voltage regulator

A voltage regulator has an output transistor that outputs an output voltage. A first circuit controls a control terminal voltage to increase the output voltage when an undershoot has occurred in the output voltage. A second circuit controls the control terminal voltage to prevent an output current from exceeding an overcurrent when the output current becomes the overcurrent, and disables the first circuit when the output current is prevented from exceeding the overcurrent so that the first circuit does not control the control terminal voltage to increase the output voltage.

Provided is a constant current circuit and a reference voltage circuit with improved line regulation without needing a start-up circuit. The constant current circuit includes: a constant current generation circuit including NMOS transistors and a resistor; a current mirror circuit including a pair of depletion mode NMOS transistors, for allowing a current of the constant current generation circuit to flow; and a feedback circuit for maintaining constant voltages of source terminals of the pair of depletion mode NMOS transistors.

Constant current circuit and reference voltage circuit

Provided is a power supply integrated circuit including an overheat protection circuit with high detection accuracy. The overheat protection circuit includes: a current generation circuit including: a first metal oxide semiconductor (MOS) transistor including a gate terminal and a drain terminal that are connected to each other, the first MOS transistor operating in a weak inversion region; a second MOS transistor including a gate terminal connected to the gate terminal of the first MOS transistor, the second MOS transistor having the same conductivity type as the first MOS transistor and operating in a weak inversion region; and a first resistive element connected to a source terminal of the second MOS transistor; and a comparator for comparing a reference voltage having positive temperature characteristics and a temperature voltage having negative temperature characteristics, which are obtained based on a current generated by the current generation circuit.

Overheat protection circuit and power supply integrated circuit

Provided is a voltage regulator capable of setting an accurate short-circuit current. Used as a circuit for determining a current value of a short-circuit current of an overcurrent protection circuit is not a resistor for converting current into voltage but a circuit for controlling in the form of current, that is, a circuit of an N-channel depletion type transistor including a gate and a drain that are connected to each other and operating in a non-saturated state. The N-channel depletion type transistor has process fluctuations that are linked with those of a detection transistor, and hence an accurate short-circuit current may be set without trimming.

Provided is a voltage regulator having a structure in which an output terminal of a first differential amplifier circuit is connected to a second differential amplifier circuit to control an output transistor by the second differential amplifier circuit. When low current consumption is required, the first differential amplifier circuit is suspended. When high-speed response is required, the first differential amplifier circuit is activated. The low-current consumption operation and the high-speed operation are switched with a minimum circuit area.

Voltage regulator operable to switch between a two-stage structure operation and a three-stage structure operation

In order to realize a reference voltage circuit that operates with lower current consumption while maintaining an operation at lower voltage without causing deterioration of a power supply rejection ratio, provided is a reference voltage circuit in which a depletion transistor of an ED type reference voltage circuit is constituted of a plurality of depletion transistors connected in series, and in which a gate terminal of a cascode depletion transistor is connected to a connection point between the depletion transistors of the ED type reference voltage circuit.

Reference voltage circuit and electronic device

Provided is a reference voltage circuit in which a temperature characteristic of a reference voltage is excellent and a circuit scale is small. In the reference voltage circuit, for example, a temperature correction circuit separated from the reference voltage circuit is not used and a difference voltage between threshold voltages of two E-type NMOS transistors (and) is added to a threshold voltage of a D-type NMOS transistor to generate a reference voltage (Vref). Therefore, the influence of the D-type NMOS transistor on the reference voltage (Vref), which is a degradation factor of the temperature characteristic of the reference voltage (Vref), may be reduced to suppress a change in tilt and curve of the reference voltage (Vref) with respect to a temperature.

Reference voltage circuit

Provided is a voltage regulator which can achieve high-speed response and is not susceptible to a ripple. An amplifier () and an amplifier () provide push-pull output to an output transistor (). Therefore, even when an idling current is small, a sink current and a source current with respect to a gate of the output transistor () can be increased in a balanced manner. Thus, the voltage regulator can easily achieve high-speed response. In addition, even when the ripple is superimposed on an input voltage, an output voltage is not influenced by the ripple.

Provided is a voltage regulator capable of performing appropriate phase compensation. Even when a difference between an input voltage and an output voltage is small, an appropriate phase compensation voltage based on an output voltage (Vout) is generated in a resistor circuit (), and the appropriate phase compensation voltage is applied to a phase compensation capacitor (). Accordingly, the voltage regulator is capable of performing appropriate phase compensation.

Voltage regulator with phase compensation

To provide a voltage regulator having improved response characteristics in case of overshoot. The voltage regulator includes: a transistor () for detecting an overshoot at an output terminal; and a current mirror circuit connected to the transistor (). If the transistor () detects the overshoot, a control transistor () is turned ON to discharge a voltage of the output terminal.

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Chiba, Japan

Takashi Imura