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A successive approximation analog/digital ("A/D") converter that converts an analog input voltage to a digital value for output in a manner enabling a reduction in power consumption. The A/D converter includes a comparator that outputs a referencing result signal by comparing an analog input voltage

A successive approximation analog/digital ("A/D") converter that converts an analog input voltage to a digital value for output in a manner enabling a reduction in power consumption. The A/D converter includes a comparator that outputs a referencing result signal by comparing an analog input voltage against a reference voltage. A D/A converter outputs the reference voltage to a comparator in correspondence to a digital voltage signal. A successive approximation register outputs the digital voltage signal to the D/A converter in correspondence to a conversion control signal. A conversion control device outputs the conversion control signal to the successive approximation register in correspondence to the referencing result signal to continue operation of the AND converter until the difference between the analog input voltage and the reference voltage converges to within a specific tolerance range. An output unit holds the digital voltage signal from the successive conversion register at a point in time at which the difference has converged to within the tolerance range and outputs the digital voltage signal as a digital output signal. An operating mode selection circuit judges an effective/non-effective state of the analog input voltage, enables an A/D conversion operation by entering a conversion mode when the analog input voltage is judged to be effective, and disables the A/D conversion operation by entering a standby mode when the analog input voltage is judged to be non-effective.

대표청구항 ▼

[ What is claimed is:] [1.] An A/D converter, comprising:a comparator that compares an analog input voltage against a reference voltage to generate a corresponding referencing result signal;a D/A converter that provides the reference voltage to the comparator in correspondence to a digital reference

[ What is claimed is:] [1.] An A/D converter, comprising:a comparator that compares an analog input voltage against a reference voltage to generate a corresponding referencing result signal;a D/A converter that provides the reference voltage to the comparator in correspondence to a digital reference signal;a successive conversion register that provides the digital reference signal to the D/A converter under control of a conversion control signal;a conversion control device that provides the conversion control signal to the successive conversion register in correspondence to the referencing result signal;an output unit that holds the digital reference signal received from the successive conversion register and generates the digital reference signal as a digital output signal under control of the conversion control device; andan operating mode selection circuit that determines whether the analog input voltage is in a first state or a second state, enables an A/D conversion operation of the analog input voltage by entering a conversion mode when the analog input voltage is determined to be in the first state and disables the A/D conversion operation of the analog input voltage by entering a standby mode when the analog input voltage is determined to be in the second state;wherein the operating mode selection circuit includes a threshold value setting unit for setting a predetermined threshold value which indicates a range for which the analog input voltage is determined to be in the first state; andwherein the operating mode selection circuit includes a judging unit that compares the digital output signal against the threshold value, judges whether the analog input voltage is in the first state or the second state, based on said comparison, and generates a judgment signal indicating the judged first state or second state state.