Touch Screen Controller Self-Test Circuitry for Connection Resistance
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Solution Overview
Problem
Existing resistive touch screen systems require manual testing to ensure connectivity to the touch screen controller chip and detect short circuits, which is costly and inefficient due to varying connection resistances and manufacturing defects.
Innovation Solution
A self-test circuitry is integrated into the touch screen digitizing system, using test switches and a comparator to automatically determine connection resistance and detect short circuits between resistive screens, allowing for automated testing within the touch screen controller chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual testing is used to detect connection failures and short circuits, then testing can be performed, but testing cost increases substantially and productivity decreases
Solution Approach 1:
The touch screen controller performs self-testing of the touch screen assembly's connectivity and short circuits using integrated test circuitry. The controller automatically applies test voltages through driver transistors, measures resulting currents via ADC, and evaluates test results without requiring external manual testing equipment or procedures.
Solution Approach 2:
The self-test circuitry performs connectivity and short circuit detection before the touch screen assembly is put into service. The controller executes test routines that proactively identify connection failures or short circuits during manufacturing or initial setup, preventing defective units from being deployed.
2Reliability
If manual testing with multiple touches is used, then connectivity can be detected, but the complexity and cost of testing procedures increases
Solution Approach 1:
The patent replaces manual mechanical testing (multiple physical touches at different points) with an automated electrical testing system. The controller uses driver transistors to apply controlled test voltages and ADC to measure resulting currents, automatically calculating connection resistance and detecting short circuits without requiring manual intervention.
Solution Approach 2:
The self-test circuitry acts as an intermediary between the controller and the touch screen assembly. It includes driver transistors that inject test signals, ADC that converts measured currents to digital values, and comparison logic that evaluates test results against expected parameters, simplifying the overall testing process.
3Reliability
If external testing circuitry is used, then comprehensive testing can be performed, but device complexity and manufacturing cost increases
Solution Approach 1:
The self-test functionality is merged into the existing touch screen controller chip. The controller integrates driver transistors for applying test voltages, ADC for measuring currents, comparison logic for evaluating results, and control circuitry for managing test routines—all within the controller itself, eliminating the need for separate external testing equipment.
Solution Approach 2:
The controller's existing components serve dual purposes: the driver transistors function both during normal touch screen operation and during self-testing; the ADC performs both coordinate digitization and current measurement for short circuit detection; the comparison logic evaluates both operational parameters and test results. This multi-functionality eliminates the need for dedicated external test hardware.
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
The solution enables convenient and cost-effective automatic testing of touch screen connectivity and short circuit detection, reducing manual testing costs and improving the reliability of touch screen systems by ensuring adequate connections and preventing short circuits.
Implementation Method 1
generate a first test voltage (xts−) on the conductor indicative of connection resistance between the first resistive screen and the touch screen controller
Implementation Method 2
an ADC (analog-to-digital converter) for digitizing x and y coordinates of touch points
Implementation Method 3
An output of the ADC is compared with a reference to determine whether the connection resistance is excessive
Data Source
AI summary
A touch screen digitizing system includes a first resistive screen and a touch screen controller including an ADC and self-test circuitry having a driver switch coupled between a reference voltage and a first terminal of the first resistive screen, and a first test switch coupled between ground and a conductor connected to generate a first test voltage on the conductor indicative of connection resistance between the first resistive screen and the touch screen controller. Another test switch couples the test voltage to an input of the ADC. An output of the ADC is compared with a reference to determine whether the connection resistance is excessive. Connection resistance between a second resistive screen and the touch screen controller is measured similarly. Similar self-test circuitry operates to detect a short circuit between the first resistive screen and the second resistive screen.