Pipeline ADC Comparator Offset Randomization for Missing Codes
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Pipeline analog-to-digital converters (ADCs) in image sensors suffer from pronounced missing codes due to capacitor mismatch, limited operational-amplifier gain, and inaccurate reference voltages, leading to degraded image quality, which existing calibration circuits attempt to mitigate but at the cost of increased power consumption and space.
Innovation Solution
Applying a randomized offset to the comparator input in the sub-ADC of the pipeline ADC to redistribute errors, making missing codes less visible or imperceptible in the digital output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If calibration circuits are included in the pipeline ADC to reduce missing codes and improve image quality, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and removes the calibration circuit from the pipeline ADC system. Instead of including calibration circuits to reduce missing codes, the invention accepts the presence of missing codes and uses a different approach (image processing techniques) to achieve the desired image quality, thereby eliminating the complex calibration circuitry.
Solution Approach 2:
The patent introduces an intermediary processing stage between the ADC output and the final image display. Rather than trying to perfect the ADC output through calibration circuits, the invention uses image processing algorithms as an intermediary to correct or mask the effects of missing codes, achieving the desired result without modifying the ADC hardware.
2Manufacturing precision
If calibration circuits are included in the pipeline ADC to reduce missing codes, then manufacturing precision is improved, but power consumption increases
Solution Approach 1:
The patent removes the power-consuming calibration circuits from the system by extracting this function and replacing it with post-processing techniques that consume less power, thereby maintaining image quality while reducing overall power consumption.
Solution Approach 2:
Instead of using hardware calibration circuits to correct missing codes, the patent creates a software/digital copy of the correction process through image processing algorithms, which can achieve similar results with lower power consumption.
3Manufacturing precision
If calibration circuits are included in the pipeline ADC to reduce missing codes, then manufacturing precision is improved, but area occupied on die increases
Solution Approach 1:
The patent extracts and removes the calibration circuit blocks from the die, eliminating the need for additional area allocation. The missing code correction function is transferred to post-processing stages that do not require physical space on the image sensor die.
Data Source
AI summary
A stage of pipeline analog to digital converter (ADC) includes a multiplying digital to analog converter (MDAC) and a sub-analog to digital converter (sub-ADC). The sub-ADC includes a comparator and a random offset controller. The comparator is coupled to compare a first analog signal received by the stage with a reference signal. The random offset controller is coupled to the comparator to apply a random offset to an input of the comparator to randomly distribute errors by the sub-ADC in a digital output of the pipeline ADC.