Segmented Ramp Signal Circuit for Linear Low-Glitch Image Sensing
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Solution Overview
Problem
Existing image sensor technologies face challenges in generating high-quality ramping signals due to issues like gain non-linearity and lost-bit effects, which are exacerbated by poor signal linearity and high glitch power, while also requiring low power consumption and a small physical area.
Innovation Solution
A system and method that utilize a series of storage circuits and current generating circuits to propagate an enable signal, converting it into a ramping signal through a load block, with an offset segment enhancing signal resolution and reducing non-linearity and glitch power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ramp signal generators are used, then the image sensor can operate, but the ramping signal exhibits poor linearity causing gain non-linearity and large glitch power causing lost-bit effects
Solution Approach 1:
The ramp signal generation is divided into multiple segments, each handled by a separate current generating circuit. Each circuit generates a portion of the ramp signal with controlled characteristics, and the segments are combined to form the complete ramp signal. This segmentation allows each segment to be optimized for linearity while managing glitch power through controlled transitions between segments.
Solution Approach 2:
Different portions of the ramp signal have different quality requirements. The invention applies local quality optimization by using storage circuits to hold and smooth specific segments of the ramp signal where glitches occur, while allowing other segments to maintain higher bandwidth. This ensures linearity in critical regions without unnecessarily constraining the entire signal path.
2Manufacturing precision
If high-quality ramping signals with improved linearity are generated, then image sensor performance is enhanced, but power consumption and physical area increase
Solution Approach 1:
The ramp signal generation uses periodic clock signals to control the timing and propagation of enable signals through storage circuits. This periodic action allows the system to generate high-linearity ramp signals at specific intervals while maintaining low power consumption during idle periods. The storage circuits are activated only when needed to hold and smooth ramp segments, reducing continuous power consumption.
3Manufacturing precision
If high-quality ramping signals with improved linearity are generated, then image sensor performance is enhanced, but the physical area of the circuit increases
Solution Approach 1:
Multiple current generating circuits are merged into a unified ramp signal generation system where they share common control structures and storage circuits. The enable signals and clock signals are distributed to multiple circuits, allowing them to cooperate in generating the ramp signal. This merging reduces the total area compared to having completely separate circuits for each ramp segment.
Solution Approach 2:
The storage circuits serve multiple functions: they hold ramp signal segments to smooth glitches, propagate enable signals through the circuit chain, and provide timing control for the current generating circuits. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby reducing the overall circuit area while maintaining signal linearity.
Data Source
AI summary
A system is provided for generating a ramping signal. The system includes a plurality of storage circuits each including an input and an output. The output of a previous storage circuit is connected to the input of a next storage circuit. The storage circuits are configured to propagate a first enable signal based on a first control signal. The system also includes a plurality of first current generating circuits. Each first current generating circuit is coupled to the output of a corresponding storage circuit to receive the propagated first enable signal. The first current generating circuits are configured to generate a first current signal based on the propagated first enable signal.