Ramp Signal Generator 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 large glitch power, which affect the quality of output, and there is a need for a signal generator with 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 optional offset segment to enhance signal resolution and reduce non-linearity, allowing for efficient generation of monotonically increasing or decreasing voltage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ramp signal generators are used, then the image sensor can function, but the ramping signal exhibits poor linearity causing gain non-linearity in column read circuits
Solution Approach 1:
The ramp signal generator is divided into multiple independent current generating circuits (first current generating circuit, second current generating circuit, etc.), each contributing a portion of the total ramp current. This segmentation allows precise control over the current contribution of each segment, improving overall linearity while reducing gain non-linearity in column read circuits.
Solution Approach 2:
Different current generating circuits are designed with different characteristics (e.g., first current generating circuit vs. second current generating circuit) to optimize specific portions of the ramp signal. This local quality approach enables tailored optimization of linearity and resolution in different regions of the ramp signal generation.
2Reliability
If conventional ramp signal generators are used, then the image sensor can operate, but large glitch power occurs causing lost-bit effect
Solution Approach 1:
The circuit design incorporates pre-charged nodes and controlled switching sequences that prepare the circuit state before ramp transitions occur. This beforehand cushioning prevents sudden current changes and glitch power spikes that would cause lost-bit effects in the image sensor output.
Solution Approach 2:
Additional current generating circuits act as intermediaries to smooth transitions between different ramp segments. These intermediary circuits buffer the transitions, reducing glitch power and preventing signal integrity issues while maintaining reliable operation.
3Manufacturing precision
If high-performance ramp signal generators are designed, then signal quality improves, but power consumption increases
Solution Approach 1:
The ramp signal generator uses multiple current generating circuits where only the necessary portions are activated at any given time. This partial action approach maintains high signal quality through precise control while avoiding the power consumption of continuously operating all circuit components at full capacity.
Solution Approach 2:
The circuit employs periodic resetting and charging cycles for the current generating circuits. Instead of continuous operation, the circuits are activated in periodic sequences, maintaining signal quality through controlled periodic action while significantly reducing average power consumption compared to continuous high-performance operation.
4Measurement precision
If high-performance ramp signal generators are designed, then signal resolution improves, but physical area increases
Solution Approach 1:
Multiple current generating circuits are merged into a unified ramp signal generation system with shared control logic and common output nodes. This merging approach achieves high signal resolution through the combined precision of multiple circuits while reducing the total physical area compared to having separate independent high-resolution generators.
Solution Approach 2:
The current generating circuits are designed with multi-functionality, where each circuit can serve multiple purposes (e.g., contributing to different portions of the ramp signal, providing both precision and resolution functions). This universality allows high signal resolution to be achieved without proportionally increasing physical area, as the same circuit structures perform multiple functions.
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.