Image Sensor Ramp Voltage Self-Test for Current Source Faults
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Solution Overview
Problem
Current methods for testing hundreds of current sources in image sensors require external inspection devices, leading to increased test time due to the influence of parasitic RC effects and other factors.
Innovation Solution
An imaging device and system that includes a control unit to generate first-phase and second-phase ramp voltages, allowing for malfunction detection of current sources without external devices, thereby omitting the need for external inspection and reducing test time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external inspection device is used to test current sources, then measurement accuracy can be improved, but test time increases due to parasitic RC effects
Solution Approach 1:
The patent extracts the malfunction detection function from the external inspection device and implements it within the imaging device itself. By generating ramp voltages internally and detecting current source malfunctions through internal circuitry, the system eliminates the need for external measurement equipment, thereby removing parasitic RC effects and reducing test time while maintaining detection accuracy
Solution Approach 2:
The patent introduces ramp voltage as an intermediary signal to detect current source malfunctions. By using the ramp voltage generated by the DAC to compare against expected values, the system can identify faulty current sources without direct external measurement, thus avoiding parasitic RC effects while preserving measurement capability
2Difficulty of detecting and measuring
If external inspection device is used for testing, then detection capability is improved, but device complexity increases
Solution Approach 1:
The imaging device is designed to perform multiple functions: normal imaging operation and current source malfunction detection. By integrating the malfunction detection capability into the existing imaging device architecture, the system eliminates the need for separate external inspection equipment, reducing overall system complexity while maintaining detection capability
Solution Approach 2:
The imaging device performs self-diagnosis by using its own internal resources (DAC, current sources, control unit) to detect malfunctions. This self-service approach eliminates dependency on external inspection devices, simplifying the overall test system while preserving detection capability
Data Source
AI summary
An imaging device according to an embodiment of the present disclosure includes: a plurality of current sources including first group current sources and second group current sources; and a control unit that controls driving of the first group current sources to generate a first-phase ramp voltage and controls driving of the first group current sources and at least one current source of the second group current sources to generate a second-phase ramp voltage.