Sensor Driving Circuit Skew Reduction via Segmented Buffers
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Solution Overview
Problem
Conventional sensor driving circuits face challenges in reducing skew between different edges of signals due to variations in rise and fall delay times and threshold voltages, which affects the timing accuracy and efficiency of image reading apparatuses.
Innovation Solution
A sensor driving circuit is designed with a first and second inverting output buffer circuit, connected in a double stage series, where the timing generator outputs a signal with the same polarity as the input, and a pre-driver is added to cancel out skew by matching the characteristics of the driver circuits, thereby reducing skew between different edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single driver is used to supply signals to reduce timing variation, then skew between same edges is reduced, but skew between different edges increases due to rise and fall delay time differences
Solution Approach 1:
The driver circuit is segmented into multiple independent driver circuits, each responsible for driving specific signals. This segmentation allows each driver to be optimized for its specific signal requirements, enabling independent adjustment of rise and fall delay times to achieve precise timing synchronization between different signal edges.
Solution Approach 2:
Each driver circuit is designed with customized characteristics tailored to its specific signal driving requirements. By assigning different driver circuits to different signals, the patent applies local quality optimization where each driver's rise and fall delay times are adjusted according to the specific timing requirements of the signals it drives, rather than using a uniform driver for all signals.
2Device complexity
If conventional driver circuits are used, then device complexity is low, but threshold voltage variations cause significant skew between different edges
Solution Approach 1:
The driver circuit is divided into multiple independent driver circuits, each capable of being independently adjusted. This segmentation enables precise control over the timing characteristics of each signal, allowing compensation for threshold voltage variations through individual driver optimization without significantly increasing overall system complexity.
Solution Approach 2:
The patent employs adjustable parameters in each driver circuit, specifically the rise delay time and fall delay time, which can be independently modified. By changing these timing parameters, the system can compensate for threshold voltage variations and maintain consistent signal timing across different edges, improving manufacturing precision without requiring complex hardware modifications.
Data Source
AI summary
There is provided a sensor driving circuit that includes: an image sensor that converts light reflected from an original to be read into electric signals; a driver circuit that drives the image sensor; and a timing generator circuit that outputs timing signals for use in control of the image sensor. The driver circuit includes a first inverting buffer circuit and a second inverting buffer circuit that are equivalent to each other and arranged in series connection of two stages with the first inverting buffer circuit at the first stage of the two stages. The timing signal output from the timing generator circuit has the same polarity as the polarity of an input signal fed to the image sensor.