Ramp Signal Generation Device for CMOS Image Sensors

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Solution Overview

Problem

CMOS image sensors face challenges in maintaining operation margin and signal quality when supply voltage is lowered, leading to non-linearity issues and degraded signal-to-noise ratio due to limitations in analog circuits like ramp signal generators.

Innovation Solution

A ramp signal generation device utilizing a plurality of local ramp signal generators, an AC coupler, and an integrator to generate and integrate ramp signals, allowing for secure operation with lower supply voltages while reducing noise and maintaining dynamic performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If supply voltage is lowered to reduce power consumption, then power efficiency is improved, but operation margin and signal quality deteriorate

Engineering Contradiction:

Improvepower consumptionVSAvoidoperation margin

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The ramp signal generation device is divided into multiple local ramp signal generators, each operating with a portion of the total ramp range. This segmentation allows each local generator to operate with sufficient voltage headroom even at reduced supply voltages, while collectively covering the full ramp range through sequential operation controlled by the control unit.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system dynamically switches between multiple local ramp signal generators based on the ramp range requirements. The control unit sequentially activates different local generators to generate ramp signals for different portions of the dynamic range, enabling the system to adapt to varying signal requirements while maintaining operation margin at lower voltages.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If supply voltage is lowered to reduce power consumption, then power efficiency is improved, but signal-to-noise ratio deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

By segmenting the ramp signal generation into multiple local generators, each handling a specific ramp range portion, the system reduces the voltage swing requirements for each local generator. This allows operation at lower supply voltages while maintaining adequate signal-to-noise ratio through controlled, segmented ramp generation rather than requiring high voltage for full-range signals.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The AC coupler acts as an intermediary between the local ramp signal generators and the integrator. It couples the ramp signals while blocking DC components, allowing the integrator to accumulate signal information without being affected by DC offsets or voltage level issues, thereby maintaining signal quality at reduced supply voltages.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If a single ramp signal generator is used, then device complexity is reduced, but non-linearity issues occur at low voltages

Engineering Contradiction:

Improvenumber of ramp signal generatorsVSAvoidlinearity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The single ramp signal generator is segmented into multiple local generators, each responsible for a specific ramp range. This segmentation improves linearity by ensuring that each local generator operates within an optimized voltage range for its specific portion, avoiding the non-linearity problems that would occur if one generator attempted to cover the full range at low voltages.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system changes the operating parameters by introducing multiple local generators with different voltage ranges. Each local generator is optimized for its specific ramp range, allowing the overall system to maintain linearity across the full dynamic range even at reduced supply voltages, whereas a single generator would exhibit non-linearity.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If multiple local ramp signal generators are used, then operation margin at low voltage is improved, but device complexity increases

Engineering Contradiction:

Improveoperation marginVSAvoidnumber of local ramp signal generators

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple local ramp signal generators are designed with identical or similar circuit topologies, allowing them to be implemented using the same design template. This multi-functionality approach provides the necessary operation margin at low voltages while minimizing the increase in device complexity through standardized, reusable circuit modules.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10805568B2Ramp signal generation device and CMOS image sensor using the same

Publication Date: 2020.10.13 SK HYNIX INC

AI summary

A ramp signal generation device may be provided to include a ramp signal generator including a plurality of local ramp signal generators, each local ramp signal generator structured to generate a local ramp signals having a local ramp range based on a control of an external control unit, an AC coupler coupled to the ramp signal generator to receive local ramp signals from the ramp signal generator, the AC couple structured to perform AC coupling on the received local ramp signals and generate AC-coupled ramp signals, and an integrator coupled to the AC coupler to receive the AC-coupled ramp signals and structured to integrate the AC-coupled ramp signals into a ramp signal having a full ramp range.