A/D converter circuit and solid-state imaging device

Abstract

Provided are a solid-state image pickup device and subranging A / D converter circuit that can effectively realize both preventing the conversion accuracy from degrading due to characteristic variations and preventing the circuit scale from increasing. There are included series-connected capacitive elements (C1-C3); a voltage comparator circuit (CMP) that compares an output value of the capacitive element (C1) with a threshold voltage value (Vth); a first input circuit that supplies an analog voltage signal (Vpix), which is to be converted, to a node between the capacitive elements (C1 and C2);a second input circuit that supplies a first reference voltage, the voltage value of which monotonously varies, to a node between the capacitive elements (C2 and C3) during execution of a first conversion process obtaining the values of higher-order bits; a third input circuit that supplies a second reference voltage, the voltage value of which monotonously varies, to an input terminal of the capacitive element (C3) during execution of a second conversion process obtaining the values of unconverted bits after completion of the first conversion process; and a control circuit (12) that generates a control signal (Vctl) for holding the first reference voltage in the capacitive element (C3) at occurrence of a change in the output of the voltage comparator circuit (CMP) in the first conversionprocess.

Description

technical field [0001] The present invention relates to an A / D conversion circuit for converting an analog signal into a digital signal, and particularly to a solid-state imaging device in which a plurality of solid-state imaging elements for converting an optical signal into an electrical signal are arranged in a matrix. A column-parallel A / D conversion circuit mounted on the same chip. Background technique [0002] A solid-state imaging element (unit pixel) that converts an optical signal into an electrical signal by photoelectric conversion, etc., including a plurality of CMOS imaging sensors, CCD sensors, near-infrared imaging sensors, and far-infrared imaging sensors, etc. is arranged as Among the solid-state imaging devices of the solid-state imaging device group formed in a matrix, there are devices in which analog circuits, digital circuits, and the like are mounted on the same chip. [0003] As a circuit mounted on the same chip as the solid-state imaging element g...

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Problems solved by technology

[0033] In addition, in the case of the column-parallel A / D conversion circuit described in Patent Document 2, for example, when the number of digits of digital data is 10, the number of high-order digits is 5, and the number of low-order digits is 5, The first conversion process takes 2 5 The time of the amount of =32 clocks, the second conversion process needs 2 5 = 32 clocks of time, so a total of 32+32=64 clocks of time is required

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