Touchscreen Sensor Self-Test Circuit for Connection Fault Isolation
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Solution Overview
Problem
Current methods for verifying the connection integrity of touch-panel sensors in touchscreens, such as those used in smartphones and interactive netbooks, are costly and time-consuming, and can fail to detect connection issues after assembly or during the sensor's lifetime, compromising functionality.
Innovation Solution
A self-test method and circuit that allows for built-in verification of sensor connections using a Wheatstone bridge sensor array, employing a finite state machine and control circuit to detect short circuits and out-of-range resistance values, enabling isolation of malfunctioning sensor branches and ensuring proper operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional EWS testing methods are used to verify sensor connection integrity, then connection verification is achieved, but product cost and test time increase
Solution Approach 1:
The sensor system performs self-testing through built-in self-test circuits that automatically verify connection integrity without requiring external EWS testing equipment. The control circuit activates test modes where sensors are sequentially connected to test circuits, allowing the system to self-diagnose connection issues and reduce external testing requirements
Solution Approach 2:
The testing functionality is merged into the existing sensor system by integrating test circuits with the sensor array and control circuitry. The same control circuit that manages sensor operation also manages testing operations, combining multiple functions into unified hardware and software components
2Reliability
If traditional EWS testing methods are used to verify sensor connection integrity, then connection verification is achieved, but product cost increases
Solution Approach 1:
The system uses built-in self-test circuits to verify connection integrity, eliminating the need for expensive external EWS testing equipment. This self-service approach reduces manufacturing costs by removing dependency on specialized external testing infrastructure
Solution Approach 2:
The control circuit serves multiple functions including normal sensor operation and testing operations. This multi-functionality reduces the need for separate dedicated testing hardware, thereby reducing overall system cost and simplifying manufacturing
3Productivity
If sensors are tested only before assembly through EWS testing, then initial connection verification is achieved, but connection failures after assembly cannot be detected
Solution Approach 1:
While maintaining preliminary testing before assembly, the system also implements continuous monitoring capabilities during operation. The control circuit can activate test modes at any time to detect connection issues that may develop during assembly or throughout the sensor's lifetime, providing both preventive and diagnostic functionality
Solution Approach 2:
The testing capability is made continuous rather than one-time only. The control circuit can repeatedly activate test modes during sensor operation to continuously monitor connection integrity, ensuring that connection issues are detected regardless of when they occur in the product lifecycle
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces product costs and test time while ensuring reliable sensor functionality by detecting and isolating faulty connections, thereby maintaining sensor integrity throughout the device's lifetime.
Implementation Method 1
Resistive force touch sensors may employ arrays of resistive Wheatstone bridge sensors. The applied force may cause a deformation of the touch panel which then causes a variation of the resistances in the Wheatstone bridge.
Implementation Method 2
The applied force may cause a deformation of the touch panel which then causes a variation of the resistances in the Wheatstone bridge.
Data Source
AI summary
A touchscreen resistive sensor includes a network of resistive sensor branches coupled to a number of sensor nodes arranged at touch locations of the touchscreen. A test sequence is performed by sequentially applying to each sensor node a reference voltage level, jointly coupling to a common line the other nodes, sensing a voltage value at the common line, and declaring a short circuit condition as a result of the voltage value sensed at the common line reaching a short circuit threshold. A current value level flowing at the sensor node to which the reference voltage level is applied is sensed and a malfunction of the resistive sensor branch coupled with the sensor node to which a reference voltage level is applied is generated as a result of the current value sensed at the sensor node reaching an upper threshold or lower threshold.