Matsushita Electric Industrial Co., Ltd.

Yoshitsugu Inagaki

Koji Oka

Heiji Ikoma

Junichi Naka

Akira Matsuzawa

Kenji Murata

Hiroyuki Konishi

Mitsuhiko Otani

Shinichi Ogita

Daisuke Nomasaki

Youichi Okamoto

Hiroshi Sakura

Yoichi Okamoto

An analog circuit includes a pulse control circuit for outputting pulse signals for operating component circuits based on reference pulse signals for driving an image sensor, a noise reduction circuit that is operated in accordance with a pulse signal of a horizontal drive frequency output from the pulse control circuit to reduce noise present in image signals output from the image sensor, a gain variable amplifier for adjusting an amplitude of signals output by the noise reduction circuit, an AD converter for converting the output signals of the gain variable amplifier into digital signals and output these digital signals, a clamp circuit that is operated in accordance with a pulse signal at a horizontal drive frequency output from the pulse control circuit to perform feedback control of the digital signals output by the AD converter, and a frequency-dependent bias circuit that supplies a current amount corresponding to the frequency of at least one kind of pulse signal from among the reference pulse signals and the pulse signals that are output from the pulse control circuit. The analog circuit is operated at a sufficient current amount required for the processing of signals from various image sensors having different horizontal drive frequency specifications.

Analog circuit for processing output signal of image sensor and imaging apparatus using the same

A semiconductor integrated circuit is provided with a reference voltage generation circuit for generating a voltage to be a reference, a function circuit that is operated using an output voltage of the reference voltage generation circuit, and a reference voltage stabilization capacitor for stabilizing the output voltage, which is connected to an output terminal of the reference voltage generation circuit. During standby, the function circuit stops operating while the reference voltage generation circuit continues operating to prevent discharging of the reference voltage stabilization capacitor, thereby realizing reduction in power consumption of the function circuit such as an analog circuit as well as high-speed recovery from the standby state to the normal operation state.

Voltage reference circuit with reduced power consumption

A start-up section is made up of an input transistor configured to receive at its gate a voltage at a node which varies with the magnitude of a current flowing in one branch of a current mirror in a reference voltage generation section, an inverter for reversing a drain voltage of the input transistor, an output transistor for supplying a start-up current to the reference voltage generation section in response to an output voltage from the inverter, and a current limit transistor serially connected to the input transistor. The current limit transistor receives a reduced gate-source voltage from the reference voltage generation section for limiting a flow of current in the input transistor upon completion of restarting the reference voltage generation section.

Reference voltage generation circuit

When the performance of an A/D converter required by a system changes, power consumption of the overall system can be reduced. The resolution of an A/D converter is made variable by changing a current flowing through an amplifier by an external control signal that specifies the resolution. Thus, when the performance required by a system changes, it is possible to change the performance of the A/D converter and to prevent a performance overhead of the A/D converter. Consequently, power consumption of the A/D converter is reduced, and power consumption of the system as a whole is also reduced.

A/D converter, method of A/D conversion, and signal processing device

An A/D converter comprises a pipeline stage array in which plural pipeline stages are connected in series, each pipeline stage performing a pipeline operation on an inputted analog voltage to output a digital voltage; a number-of-bits control circuit for outputting a number-of-bits selection signal which indicates whether the operation of each pipeline stage should be carried out or halted, according to a number-of-bits control signal which indicates a resolution; and a correction circuit for compensating a digital value to be output, according to the number-of-bits control signal. Therefore, when resolution of the A/D converter, which is requested by the system, is changed, only the pipeline stages required for realizing the requested resolution are operated while the other pipeline stages are halted, whereby a reduction in power consumption of the A/D converter is realized and, simultaneously, a breakdown of an output from the A/D converter is avoided.

A/D converter for performing pipeline processing

A current steering type D/A converter comprises a D/A conversion circuit having plural current sources each outputting a predetermined current, and a logic circuit for selecting desired current sources from among the plural current sources; a reference voltage generation circuit for generating a reference voltage potential that determines an output current value of the D/A conversion circuit; and a control circuit for setting the D/A conversion circuit in the ON state or OFF state by controlling switch elements which are placed between the D/A conversion circuit and the reference voltage generation circuit. Therefore, current consumption of the current steering type D/A converter can be reduced.

Current steering type D/A converter

A monitor circuit for supplying a detection voltage reflecting a supply voltage, a reference voltage generation circuit for generating a high-precision reference voltage not depending upon the supply voltage, and a comparator for comparing the detection voltage with the reference voltage and outputting the result of the comparison are provided and, in addition, a controller is provided which is made up of an auxiliary reference voltage generation circuit for generating a low-precision auxiliary reference voltage with less power dissipation and an auxiliary comparator for comparing the detection voltage with the auxiliary reference voltage. The auxiliary reference voltage is set higher than the reference voltage, and when the detection voltage becomes higher than the auxiliary reference voltage to cause the comparison output of the auxiliary comparator to become active, the reference voltage generation circuit is placed in a power-down state, thereby achieving a reduction in current dissipation.

Supply voltage detection circuit

In order to reduce power consumption, a power supply for a digital circuit portion is shut off, so that the output voltage of the power supply becomes the zero level. A CMOS (complementary metal oxide semiconductor) inverter has a P-channel FET (field effect transistor) with a gate electrode formed of P-type polysilicon. A source electrode of the P-channel FET is connected to the power supply and a back gate electrode of the P-channel FET is in direct connection with the aforesaid source electrode. The P-channel FET is placed in a state of not functioning as a transistor when the power supply is shut off in a low power consumption mode. However, in order to prevent the P-channel FET from undergoing characteristic degradation in that mode, there is the provision of a pull-down switch capable of fixing, in the mode, the voltage of the gate electrode of the P-channel FET at the zero level.

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Osaka, Japan

Yoshitsugu Inagaki