Quadratic Ramp ADC Conversion for High-Resolution Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current analog to digital converters (ADCs) face challenges in achieving high data resolution and high frame rates while maintaining low complexity, leading to undesirable distortion and increased size, particularly when dealing with high-bit conversions in image sensors.
Innovation Solution
The method involves generating a quadratic signal based on an analog time-varying reference signal to create a ramp signal for analog to digital voltage conversion, allowing for efficient conversion by comparing the analog input voltage with the ramp signal's time duration, and using a counter to store the digital output value, which can be linearized to achieve higher bit precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of bits of the ADC is increased to achieve high data resolution, then the conversion precision is improved, but the conversion time increases and the device complexity increases
Solution Approach 1:
The patent changes the temporal parameter of the ramp signal by using a quadratic time variation instead of a linear one. The ramp signal follows a quadratic curve y = ax² + bx + c, which allows the signal to traverse the conversion range more efficiently, reducing the time required for high-bit conversions while maintaining precision.
Solution Approach 2:
The patent introduces dynamic adjustment of the ramp signal characteristics by making the slope variable through quadratic time dependence. The instantaneous slope of the ramp signal changes dynamically during conversion, allowing faster traversal of the conversion range compared to a static linear ramp, thus reducing conversion time for high-resolution ADCs.
2Measurement precision
If the number of bits of the ADC is increased to achieve high data resolution, then the conversion precision is improved, but the device complexity and size increase
Solution Approach 1:
The patent changes the functional form of the ramp signal from linear to quadratic, which allows achieving the same conversion precision with a smaller counter width. By using the quadratic relationship, the effective resolution is enhanced without proportionally increasing the counter size, thus reducing device complexity for high-bit ADCs.
3Ease of manufacture
If a linear ramp signal is used for conversion, then the circuit implementation is simple, but the signal quality and sensitivity at extreme light levels is degraded
Solution Approach 1:
The patent changes the time-variation parameter of the ramp signal from linear to quadratic. This modification improves signal quality at extreme light levels (both low and high ends of the dynamic range) by providing better differentiation capability, while the overall circuit structure remains relatively simple and implementation-friendly.
Data Source
AI summary
A method of analog to digital voltage conversion including: generating a quadratic signal based on an analog time varying reference signal; generating a ramp signal based on the quadratic signal; and converting an analog input voltage to a digital output value based on a time duration determined by a comparison of the analog input voltage with the ramp signal.