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Cyclic ADC structure with CDS function

A technology of function and circuit structure, which is applied in the design of CyclicADC (cyclic analog-to-digital conversion circuit) readout circuit and the field of digital domain accumulating CMOS image sensor, which can solve the problem that the conversion speed and accuracy are not high enough, and the area and power consumption of the readout circuit are increased. and other problems to achieve the effect of simple structure

Pending Publication Date: 2021-02-23
TIANJIN UNIV MARINE TECH RES INST
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  • Application Information

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Problems solved by technology

Most of the current Cyclic ADC readout circuits add a CDS circuit in front of the ADC to complete the CDS and amplification processing of the pixel output signal, but this part of the circuit will increase the area and power consumption of the readout circuit; Some circuits add the CDS function to the ADC circuit, which saves area and power consumption, but the conversion speed and accuracy are not high enough

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  • Cyclic ADC structure with CDS function
  • Cyclic ADC structure with CDS function
  • Cyclic ADC structure with CDS function

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Embodiment Construction

[0019] The present invention will be described in detail below according to the drawings and embodiments, but the protection scope of the present invention is not limited thereto.

[0020] figure 1 Clarify the working method of Cyclic ADC in the form of structural block diagram: the switch hits V in the first cycle in On, the analog signal output by the previous stage is sampled, and the switch is switched to the residual difference signal V output by the MDAC in the next cycle out superior. The input signal enters the 1.5-bit sub-ADC with the reference voltage V ref For comparison, the output code value controls the output of the sub-DAC on the one hand, and the output of the DAC is compared with the total input signal to obtain the V of the cycle out , and then control the progress of the next cycle. On the other hand, the output code value is input into the RSD encoding circuit, so that finally after N cycles, an N-bit digital output code value can be obtained. Thus, t...

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Abstract

The invention discloses a Cyclic ADC structure with a CDS function. The Cyclic ADC structure mainly comprises a 1.5-bit comparator, namely a sub ADC, a 1.5-bit digital-to-analog conversion circuit, namely a sub DAC, a double operational amplifier and an RSD coding circuit, wherein the sub DAC and the double operational amplifier jointly form an MDAC, namely a multiplication DAC, and the CDS function is achieved through an improved MDAC circuit structure. The structure aims to realize a high-speed and high-precision Cyclic ADC reading circuit with as small area and power consumption as possible, and the reading circuit provided by the invention not only has a basic CDS function, but also can realize a signal gain adjustment function through a programmable capacitor array.

Description

technical field [0001] The invention relates to the field of readout circuits of CMOS (complementary metal oxide semiconductor) image sensors, and is mainly used in high-speed and high-precision digital domain accumulation CMOS image sensors, and in particular relates to the design of Cyclic ADC (cyclic analog-to-digital conversion circuit) readout circuits. Background technique [0002] Due to factors such as process and temperature, there is a certain degree of mismatch between the transistors in the pixel unit of the CMOS image sensor. These mismatches will cause fixed pattern noise in the pixel unit, which is generally output to the pixel through a CDS (correlated double sampling) structure. The analog signal is processed to eliminate this part of the noise, and then the processed analog signal is sent to the ADC (analog-to-digital conversion circuit) for analog-to-digital conversion. Most of the current Cyclic ADC readout circuits add a CDS circuit in front of the ADC t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03M1/12H03M1/40H03M1/46
CPCH03M1/1245H03M1/403H03M1/466
Inventor 徐江涛李婷婷聂凯明高志远查万斌
Owner TIANJIN UNIV MARINE TECH RES INST