Image Sensor Shared Terminal Multiplexing Clock Control Signals
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Solution Overview
Problem
The miniaturization of CMOS image sensors is limited by the size and pitch of bonding pads, making it difficult to accommodate the necessary number of pads on smaller semiconductor dies, particularly in medical applications where smaller image sensors are required for endoscopes.
Innovation Solution
The implementation of an image sensor system with a reduced number of terminals, where a single terminal is used for multiple functions, such as transferring clock signals and digital control signals, allowing for a smaller form factor while maintaining functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of bonding pads is increased to accommodate all necessary signals, then the functionality and reliability are improved, but the die area is increased making miniaturization difficult
Solution Approach 1:
The patent applies multi-functionality by enabling a single bonding pad to serve multiple purposes: transmitting both clock signals and control signals to the image sensor. This is achieved through a controller that multiplexes control signals onto the clock signal line, allowing the clock pad to function as both a clock input and a control signal input, thereby reducing the total number of pads required and enabling die miniaturization while maintaining full functionality
2Adaptability or versatility
If the image sensor size is reduced for medical applications, then the adaptability to medical devices is improved, but the number of bonding pads that can be accommodated is reduced
Solution Approach 1:
The patent enables medical device adaptability by reducing the image sensor size through multi-functional bonding pads. The controller multiplexes control signals onto the clock signal transmission line, allowing smaller dies to accommodate all necessary signals with fewer pads, thus enabling deployment in compact medical devices like endoscopes while maintaining full operational capability
Solution Approach 2:
The patent employs periodic action through time-division multiplexing where control signals are transmitted during specific time intervals (e.g., during vertical blanking periods or between frame transfers) when the clock signal is not being used for primary imaging operations. This periodic insertion of control signals allows efficient use of the shared clock pad without interfering with normal image data transmission
3Area of stationary object
If the bonding pad pitch is reduced to fit more pads on smaller dies, then the die area is reduced, but the manufacturing precision requirements are increased
Solution Approach 1:
The patent extracts the control signal transmission function from dedicated control pads and relocates it to the existing clock pads through signal multiplexing. This eliminates the need for separate control pads with tight pitch requirements, allowing larger pad spacing and relaxed manufacturing precision requirements while maintaining all necessary signal transmission capabilities on smaller dies
Data Source
AI summary
An example image sensor system includes an image sensor having a first terminal and a host controller coupled to the first terminal. Logic is included in the image sensor system, that when executed transfers clock signals from the host controller to the image sensor through the first terminal of the image sensor and also transfers one or more digital control signals between the image sensor and the host controller through the same first terminal.