Ramp Voltage Generator Using Boost Current for Faster Image ADC
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current image sensors face challenges in achieving high frame rates and high-resolution, high-speed operations, particularly in portable devices, due to limitations in analog-to-digital conversion and noise reduction, especially with the increasing number of pixels and frame rates.
Innovation Solution
The implementation of a ramp voltage generator that supplies a ramp voltage for comparison operations in the analog-to-digital conversion circuit, utilizing a combination of bias and boost currents to quickly reach and maintain a target level, thereby reducing noise and enhancing conversion speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional analog-to-digital conversion methods are used in image sensors, then device complexity is reduced, but conversion speed and noise reduction performance deteriorate
Solution Approach 1:
The analog-to-digital conversion process is divided into multiple stages: first converting pixel signals to intermediate digital values, then performing second conversion on grouped intermediate values. This segmentation allows faster initial conversion while maintaining overall system performance
Solution Approach 2:
An intermediate digital value is introduced as a mediator between the analog pixel signal and the final digital output. This intermediate representation enables staged conversion, improving overall conversion speed while managing complexity
2Measurement precision
If the number of pixels and frame rate are increased, then image quality and temporal resolution are improved, but noise increases and conversion becomes slower
Solution Approach 1:
Pixel signals are converted in segments rather than all at once. The conversion process handles signals in groups through multiple stages, enabling the system to maintain high frame rates while processing large numbers of pixels with improved noise performance
Solution Approach 2:
The first conversion stage performs preliminary digital conversion of pixel signals before the second conversion stage. This preliminary action prepares the data in an intermediate format that facilitates faster subsequent processing and better noise management
Data Source
AI summary
An analog-to-digital conversion circuit includes a convertor configured to perform a first comparison operation for sensing a noise based on a reset signal and to perform a second comparison operation for sensing raw data to output data which is obtained by removing the noise from the raw data, and a ramp voltage generator configured to generate a ramp voltage used for the first comparison operation and the second comparison operation and to output the ramp voltage to the convertor. The ramp voltage generator includes a first current source for supplying a bias current for generating the ramp voltage in response to a first control signal, a second current source for supplying a boost current for generating the ramp voltage in response to a second control signal, and a generation circuit for generating the ramp voltage based on the bias current and the boost current.