SAR ADC Noise Detection for Accurate Solid-State Imaging
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Solution Overview
Problem
Existing analog-digital conversion circuits, such as SARADC, are susceptible to errors due to power noise fluctuations in pixel power output, which affect the accuracy of signal conversion.
Innovation Solution
A solid state imaging element with a successive approximation type analog-digital conversion circuit and a noise detection circuit that detects power noise and adjusts gain and phase to cancel out noise interference at the comparator level, ensuring accurate digital conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional SARADC is used for analog-digital conversion, then the device maintains small power consumption and compact size, but power noise from the pixel array causes errors in the comparator output and reduces conversion accuracy
Solution Approach 1:
A noise detection circuit is introduced as an intermediary component that detects power noise at the DAC output node and generates a correction signal to compensate for the noise's effect on the comparator output, thereby improving conversion accuracy without increasing overall device complexity
Solution Approach 2:
The noise detection circuit continuously monitors the DAC output node for power noise and feeds back a correction signal to the comparator or SAR logic, enabling real-time compensation that maintains high conversion accuracy despite the presence of power noise from the pixel array
2Measurement precision
If noise correction circuitry is added to mitigate power noise influence, then conversion accuracy improves, but device complexity increases
Solution Approach 1:
The noise detection circuit is localized to monitor only the critical DAC output node where power noise has the most significant impact, rather than implementing system-wide noise correction, thereby achieving effective noise mitigation with minimal additional circuit complexity
Solution Approach 2:
The noise detection circuit creates a copy or representation of the noise signal present at the DAC output and uses this copied signal to generate the appropriate correction, avoiding the need for complex direct noise cancellation while maintaining accuracy
Data Source
AI summary
A solid state imaging element (100) includes: a successive approximation type analog-digital conversion circuit (140) converting an analog pixel signal received from a pixel of a pixel array portion (110) to a digital code; and a first noise detection circuit (130-1) connected to a DAC (Digital to Analog Converter) output node inside the successive approximation type analog-digital conversion circuit (140) and detecting power noise supplied to the pixel of the pixel array portion (110) to output a detection result to the DAC.