Image Sensor ADC Counter Test Circuit for Accurate Counting
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Solution Overview
Problem
Current image sensors lack an effective method for testing the counting operations of their analog-to-digital converters (ADCs), which is crucial for obtaining clear image data, as existing testing methods are inadequate and do not ensure the accuracy of the counting processes.
Innovation Solution
Incorporating a test logic circuit within the image sensor that receives a test code, generates a count clock signal, and tests the counting operation of the counter, allowing for the external output of a test result through a test terminal, thereby ensuring the accuracy of the counting process and improving image data clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a test logic circuit is added to test the counter operation, then the measurement precision of the counting operation is improved, but the device complexity increases
Solution Approach 1:
The test logic circuit is integrated within the image sensor device, merging the testing function with the existing sensor structure. The test logic includes a test code input unit, count clock signal generation unit, and test result output unit that work together with the existing counter and ADC components, eliminating the need for external testing equipment and reducing overall system complexity.
Solution Approach 2:
The counter unit serves dual purposes: it performs normal counting operations during image data conversion and performs test counting operations when receiving test codes. The same counter infrastructure is utilized for both production and testing functions, avoiding the need for separate dedicated test counters and reducing device complexity.
2Device complexity
If existing testing methods are used, then the device complexity remains low, but the measurement precision of the counting operation is insufficient
Solution Approach 1:
The test logic circuit implements a feedback mechanism where the counter's counting operation is monitored and compared against expected results generated from test codes. The test result output unit provides feedback about the accuracy of the counting operation, enabling precise measurement and verification of counter performance without adding excessive complexity.
Solution Approach 2:
Test codes are pre-generated and stored within the test logic circuit before actual testing occurs. The count clock signal generation unit prepares test sequences in advance, allowing the counter to be tested with known input patterns that verify its counting accuracy without requiring complex external testing equipment.
Data Source
AI summary
An image sensor includes a pixel array, an analog-to-digital converter (ADC), and a test circuit. The pixel array includes a plurality of pixels arranged in rows and columns. Each pixel generates an analog signal based on incident light. The ADC converts the analog signal to a digital signal using a counter. The test circuit receives a test code in a test mode, generates a count clock signal based on the test code, tests a counting operation of the counter according to the count clock signal, and externally outputs a test result of the counter through a test terminal.