Image Sensor Pixel Circuit Using Reset Transistor Ramp Sharing
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Solution Overview
Problem
Conventional image sensors face challenges in reducing circuit layout area, number of circuit components, and signal routings due to the complexity of pixel circuits, which hinders the miniaturization and resolution enhancement of image sensors.
Innovation Solution
The image sensor employs a pixel circuit with a driving transistor, selection transistor, transfer transistor, reset transistor, and sensing unit, utilizing a single reset transistor to receive different signals for reset and analog-digital conversion operations, eliminating the need for additional ramp capacitances and signal routing, thereby saving circuit layout space and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple transistors and capacitances are used in the pixel circuit to achieve reset and ADC operations, then the circuit functionality is complete, but the circuit layout area increases
Solution Approach 1:
The reset transistor is configured to perform multiple functions: during the reset period, it receives the reset signal to reset the floating diffusion node; during the sensing period, it receives the ramp signal to enable ADC operation. This multi-functionality eliminates the need for separate dedicated transistors and capacitances for each operation, thereby reducing the overall circuit layout area while maintaining complete circuit functionality
Solution Approach 2:
The patent merges the reset function and ADC function into a single reset transistor by configuring its control terminal to receive different signals (reset signal during reset period, ramp signal during sensing period) from the same signal line. This consolidation combines multiple circuit elements into one, reducing the number of components and routing while preserving both reset and ADC operations
2Adaptability or versatility
If additional ramp capacitances and signal routing are added to the pixel circuit, then the ADC operation is enabled, but the circuit complexity increases
Solution Approach 1:
The reset transistor serves dual purposes: resetting the pixel during the reset period and enabling ADC during the sensing period. By making the reset transistor universal, the patent eliminates the need for additional dedicated components for ADC operation, thereby reducing circuit complexity while maintaining full ADC capability
Solution Approach 2:
The patent combines the reset signal line and ramp signal line into a single signal line that connects to the control terminal of the reset transistor. This merging of signal routing reduces the number of separate connections and components needed, simplifying the overall circuit structure while enabling both reset and ADC operations
Data Source
AI summary
Disclosed are an image sensor and an image sensing method. The image sensor includes a first pixel circuit. The first pixel circuit includes a first driving transistor, a first selection transistor, a first transfer transistor, a first reset transistor and a first sensing unit. A control terminal of the first selection transistor is used for receiving a first selection signal. A control terminal of the first transmitting transistor is used for receiving a first transmitting signal. The image sensing method includes the following steps: receiving a first reset signal during a reset period through a control terminal of the first reset transistor; and receiving a first ramp signal during a sensing period through a control terminal of the first reset transistor.