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Two-step successive approximation analog-to-digital converter applied to image sensor

An analog-to-digital converter and successive approximation technology, applied in image communication, color TV components, TV system components, etc., can solve the problems of occupied area and power consumption, and achieve the effect of reducing area and power consumption

Pending Publication Date: 2022-07-29
HUAZHONG UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This two-step SAR ADC consists of two DACs, two comparators, two logic blocks, and a difference amplifier. The number of unit capacitance required to achieve N-bit accuracy is Still occupy more area and power consumption

Method used

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  • Two-step successive approximation analog-to-digital converter applied to image sensor
  • Two-step successive approximation analog-to-digital converter applied to image sensor
  • Two-step successive approximation analog-to-digital converter applied to image sensor

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Embodiment 1

[0046] To address the aforementioned issues, see image 3 This embodiment provides a two-step SAR ADC applied to an image sensor. The two-step SAR ADC includes: a sampling module 1, an amplification module 2, a digital-to-analog conversion module 3 and a switch module; the sampling module 1 passes through the switch module and the amplification module. 2 is connected, and the amplification module 2 is connected with the digital-to-analog conversion module 3.

[0047] In this embodiment, the switch module has a first working state, a second working state and a third working state, the switch module includes a plurality of switch circuits, and the plurality of switch circuits are selectively turned on to selectively switch the switch module to be in the The first working state, the second working state or the third working state; when the switch module is in the first working state, the sampling module 1 is used to send the acquired original signal to the amplifying module 2, an...

Embodiment 2

[0065] see Figure 4 , combined with the signal flow, describe each functional module in detail from left to right:

[0066] The fourth switch circuit 44 mainly includes five ports, specifically a pair of differential input ports, a pair of differential output ports, and a control port PH1; a pair of differential input ports are used to receive original signals in differential form, and a pair of differential output ports are used for After the original signal is input to the sampling module 1, the on-off of a pair of fourth switches S4 is controlled by the control signal PH1, so as to switch the working state of the switch module.

[0067] Sampling module 1 mainly samples and holds the original differential signal that needs to be converted into analog-to-digital. This module has four main ports, including a pair of differential input ports, from which the original signal is input; a pair of differential output ports and subsequent amplification module 2 connected. The swit...

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Abstract

The invention discloses a two-step successive approximation analog-to-digital converter applied to an image sensor. The two-step successive approximation analog-to-digital converter comprises a sampling module, an amplification module, a digital-to-analog conversion module and a switch module, the sampling module is connected with the amplification module through the switch module. The amplification module is connected with the digital-to-analog conversion module. The switch module has a first working state, a second working state and a third working state, the switch module comprises a plurality of switch circuits, and the plurality of switch circuits are selectively conducted so as to selectively switch the switch module to be in the first working state, the second working state or the third working state. According to the invention, a two-step analog-to-digital converter is realized only by using a single DAC, 2N-bit analog-to-digital converter precision is obtained only by using an N-bit capacitive digital-to-analog converter, and the area and power consumption of the analog-to-digital converter are remarkably reduced. Especially for the application of an image sensor column-level reading circuit which needs high precision and is strictly limited in area, the method has remarkable advantages.

Description

technical field [0001] The present application relates to the technical field of integrated circuits, in particular to a two-step successive approximation analog-to-digital converter (SAR ADC, Successive Approximation Register Analog-to-Digital Converter) applied to an image sensor. Background technique [0002] In a CMOS (Complementary Metal Oxide Semiconductor) image sensor, the quality of the readout circuit design has a significant impact on the image quality, especially the design of the analog-to-digital conversion circuit module in the readout circuit. The image sensor readout circuit has a huge array of pixel circuits. Each pixel converts the optical signal into an analog voltage signal output and requires subsequent analog-to-digital conversion. Based on the compromise between speed and area, the analog-to-digital conversion in the readout circuit is widely used. The column parallel architecture is implemented, that is, each column has a separate ADC (Analog-to-Digi...

Claims

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Application Information

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IPC IPC(8): H04N5/378
CPCH04N25/75
Inventor 刘冬生聂正李豪唐江牛广达高亮
Owner HUAZHONG UNIV OF SCI & TECH