Reference Voltage Generator Noise Cancellation CMOS Image Sensor

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Solution Overview

Problem

CMOS image sensors face significant horizontal noise due to power noise, particularly switching noise, which is not effectively cancelled in the readout circuit and is included in the pixel data, necessitating a solution to suppress or cancel this noise.

Innovation Solution

A reference voltage generator is designed with a power supply for the switching operation-associated section, utilizing a diode-connected MOS and current to efficiently cancel or suppress power noise by transferring pixel and reference signals to the comparator's input terminals based on the same power supply, preventing switching noise from being transferred to the readout circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the reference voltage generator uses the pixel power supply, then power noise is suppressed, but the readout circuit is affected by switching noise from the reference voltage generator

Engineering Contradiction:

Improvepower noiseVSAvoidsignal quality

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The power supply is segmented into two independent systems, with the reference voltage generator using a separate second power supply from the pixel's first power supply. This segmentation isolates the readout circuit from switching noise generated by the reference voltage generator's switching operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The diode-connected MOS transistor serves as an intermediary that enables the reference voltage generator to operate from a separate power supply while maintaining proper voltage level compatibility, thus preventing noise transfer while ensuring system functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively cancels or suppresses power noise, reducing horizontal noise in CMOS image sensors by using a diode-connected MOS and current, ensuring that pixel signals are not distorted by power noise, thereby improving image sensor performance.

Implementation Method 1

utilizing a diode-connected MOS and current to efficiently cancel or suppress power noise

Methodology Applied

Scientific EffectDiode-connected MOS effect:

Data Source

PatentUS9584110B2Reference voltage generator having noise cancelling function and CMOS image sensor using the same

Publication Date: 2017.02.28 SK HYNIX INC

AI summary

The reference voltage generator may include a reference current generation unit suitable for generating a reference current based on a first power supply voltage and a first ground voltage, a current amount adjustment unit suitable for adjusting a current amount of the reference current generated by the reference current generation unit based on a second power supply voltage and a second ground voltage, and a reference voltage generation unit suitable for generating a reference voltage corresponding to the reference current, of which the current amount is adjusted by the current amount adjustment unit, based on the first power supply voltage and the first ground voltage.