Touchscreen Sensor Self-Test Circuit for Open and Short Detection
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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, which includes a self-test node, a source circuit, a control circuit, and a finite state machine to detect open tests, short circuits, and out-of-range resistance values, enabling isolation of malfunctioning sensor branches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional EWS testing methods are used to verify sensor connection integrity, then connection verification can be performed, but product cost and test time increase
Solution Approach 1:
The sensor system performs self-testing through built-in self-test circuits integrated within the sensor module. The sensor can autonomously verify its own connection integrity and report status without requiring external EWS testing equipment, thereby reducing test time and cost while maintaining reliability.
Solution Approach 2:
A dedicated self-test circuit acts as an intermediary between the sensor and external testing systems. This intermediate circuit enables connection verification through simple electrical measurements that can be performed quickly during manufacturing or in-field diagnostics, eliminating the need for complex traditional testing procedures.
2Reliability
If traditional EWS testing methods are used to verify sensor connection integrity, then connection verification can be performed, but product cost increases
Solution Approach 1:
The sensor system performs self-testing through built-in self-test circuits integrated within the sensor module. The sensor can autonomously verify its own connection integrity and report status without requiring external EWS testing equipment, thereby reducing test time and cost while maintaining reliability.
Solution Approach 2:
A dedicated self-test circuit acts as an intermediary between the sensor and external testing systems. This intermediate circuit enables connection verification through simple electrical measurements that can be performed quickly during manufacturing or in-field diagnostics, eliminating the need for complex traditional testing procedures.
3Productivity
If sensors are tested only before assembly through EWS testing, then initial connection verification is possible, but connection failures after assembly cannot be detected
Solution Approach 1:
The self-test circuit is pre-configured within the sensor module during assembly, enabling immediate verification of connection integrity as soon as the sensor is installed. This preliminary setup allows for quick diagnostics and eliminates the need for separate post-assembly testing steps, ensuring reliability without compromising productivity.
Solution Approach 2:
The self-test capability enables continuous monitoring of sensor connection status throughout the sensor's operational lifetime. The sensor can periodically self-diagnose or respond to diagnostic requests, ensuring ongoing reliability rather than relying on a single pre-assembly test point.
4Reliability
If built-in self-test circuits are integrated into the sensor, then real-time verification is possible, but device complexity increases
Solution Approach 1:
The self-test circuit is merged with the existing sensor circuitry, sharing common components such as signal lines, power supply, and processing logic. This integration approach enables real-time verification capability while minimizing the addition of separate dedicated components, thereby limiting the increase in device complexity.
Solution Approach 2:
The self-test circuit is designed to be universal and multi-functional, using the same hardware resources for both normal sensor operation and self-diagnosis. The circuit can perform multiple functions including connection verification, analog-to-digital conversion, and status reporting, reducing the need for separate dedicated components and minimizing complexity overhead.
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 allowing for real-time verification of sensor connections and isolating faulty branches, ensuring proper operation of the touchscreen.
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.