CMOS Image Sensor Row Driver Shoot-Through Current Control

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Solution Overview

Problem

Signal line drivers in CMOS imaging devices are susceptible to unwanted 'inter' and 'intra' shoot-through currents, leading to noise in captured images due to asynchronous switching of buffers, which results in current spikes and noise in image signals.

Innovation Solution

The implementation of a dual row driver architecture with global controllers and timing information units to manage signal transmission, using protection transistors and finite state machines to synchronize and isolate signal outputs, preventing shoot-through currents by controlling the transmission of high and low voltage signals during lag periods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If dual row driver architecture is used to reduce signal propagation delay, then speed is improved, but shoot-through current occurs due to asynchronous switching

Engineering Contradiction:

Improvesignal propagation delayVSAvoidshoot-through current

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

A control mechanism acts as an intermediary between the left and right buffers, coordinating their switching operations. The control mechanism generates enable signals that ensure both buffers switch states simultaneously, preventing the asynchronous switching that causes shoot-through current while maintaining the speed benefits of the dual row driver architecture

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If buffers switch asynchronously to simplify control, then device complexity is reduced, but current spikes and noise are generated

Engineering Contradiction:

Improvecontrol mechanism complexityVSAvoidcurrent spikes and noise

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The control mechanisms for the left and right buffers are merged into a single coordinated control system. This unified control approach ensures synchronized switching of both buffers, eliminating the current spikes and noise generated by asynchronous switching while maintaining relatively simple device architecture

Inventive Principle:

Principle #5Merging (Combining)

3Ease of operation

If left and right buffers drive signal lines independently, then ease of operation is improved, but inter shoot-through current occurs between buffers

Engineering Contradiction:

Improvebuffer control independenceVSAvoidinter shoot-through current

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The control mechanism incorporates feedback from both the left and right buffer states to generate coordinated enable signals. This feedback mechanism ensures that the buffers switch states in unison, preventing inter shoot-through current while maintaining ease of operation through automated synchronized control

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8035718B2Systems, methods, and devices for preventing shoot-through current within and between signal line drivers of semiconductor devices

Publication Date: 2011.10.11 APTINA IMAGING CORP

AI summary

An imaging device driver for transmitting a signal onto a signal line for controlling transistors of a pixel row. The device includes a controller and associated circuitry for reducing shoot-through current within and between row driver circuits for driving the signal line. The controller reduces shoot-through current by preventing concurrent transmission of high and low signal outputs to the signal line by respective high and low voltage sources of the same or different row driver circuits.