Image Sensor Booster Circuit Noise Rejection
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Solution Overview
Problem
Image sensors in electronic devices face challenges with power supply noise rejection, as booster circuits generate high voltage with significant noise components, which propagate through the circuitry and deteriorate image sensor operations.
Innovation Solution
The implementation of a noise cancellation signal, which is an inverted version of the power supply noise, is used to cancel out the unwanted noise at the floating diffusion region of the image sensor pixels, reducing the impact of power supply noise on image signal readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a booster circuit is used to reduce input supply voltage, then power delivery capability is improved, but output noise increases
Solution Approach 1:
The patent captures the noise signal generated by the booster circuit and uses it as a reference input to a noise cancellation circuit. The noise cancellation circuit processes this reference signal and generates an inverted noise signal that is then subtracted from the pixel output signal, converting the harmful noise into a useful reference for cancellation.
Solution Approach 2:
The patent introduces a noise cancellation circuit as an intermediary component between the booster circuit and the pixel readout path. This intermediary circuit receives both the pixel signal and the booster noise reference, processes them through differential amplification, and outputs a noise-rejected signal, effectively mediating the interaction between the power supply and signal paths.
2Power
If power supply voltage is increased to meet pixel power demands, then power delivery is improved, but power supply noise increases
Solution Approach 1:
The patent implements a feedback mechanism where the noise cancellation circuit continuously monitors the pixel output signal and the booster reference signal, processes the difference through differential amplification, and feeds back the corrected signal. This feedback loop enables dynamic noise rejection that adapts to varying noise conditions while maintaining proper power delivery.
3Device complexity
If a single regulator circuit is used to distribute power, then circuit complexity is reduced, but input supply voltage requirement increases
Solution Approach 1:
The patent segments the power delivery function by separating the voltage boosting function (performed by the booster circuit) from the voltage regulation function (performed by the regulator circuit). This segmentation allows the system to use a lower input supply voltage while still achieving the necessary output voltage levels, reducing the stress on the input power supply.
Data Source
AI summary
An image sensor may include an array of pixels having an active pixel. The active pixel may generate image signals in response to incident light. The image sensor may also include a power supply and booster circuitry. The power supply may provide a powers supply voltage signal, which has a first noise component, to the active pixel. The booster circuitry may provide a control signal, which has a second noise component that is the inverted version of the first noise component, to the active pixel. The control signal with the second noise component may be used to reject the first noise component, which is an unwanted noise component (e.g., power supply noise). The booster circuitry may include an operational amplifier, capacitors, and switches coupled to two input terminals and one output terminal of the operational amplifier in various configurations.