Touch Sensor Interface Circuit Using Frequency-Domain Signal Merging
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Solution Overview
Problem
Existing touch sensor technologies face scalability issues with larger screen sizes and higher touch resolutions due to increased scan times when reading individual columns and rows one at a time, which results in higher costs, power consumption, and larger interface circuitry when additional ADCs are added.
Innovation Solution
A method and apparatus that apply simultaneous sets of column and row input signals to a touch sensor, combining output signals into frequency-domain signals for detection, allowing for simultaneous reading of all columns and rows with reduced component count and improved scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If additional ADCs are added to reduce scan times, then reading speed is improved, but cost and device complexity increase
Solution Approach 1:
The patent combines multiple column and row signals into single composite signals that can be processed by fewer ADCs. Specifically, column signals from multiple columns are combined into a single combined column signal, and row signals from multiple rows are combined into a single combined row signal, allowing one ADC to process what previously required multiple ADCs.
Solution Approach 2:
The patent makes a single ADC perform multiple functions by having it process both combined column signals and combined row signals. The same ADC that would traditionally be dedicated to one column or row now handles composite signals containing information from multiple columns or rows, reducing the total number of ADCs needed.
2Speed
If additional ADCs are added to reduce scan times, then reading speed is improved, but power consumption increases
Solution Approach 1:
The patent combines multiple column and row signals into single composite signals that can be processed by fewer ADCs. Specifically, column signals from multiple columns are combined into a single combined column signal, and row signals from multiple rows are combined into a single combined row signal, allowing one ADC to process what previously required multiple ADCs.
Solution Approach 2:
The patent makes a single ADC perform multiple functions by having it process both combined column signals and combined row signals. The same ADC that would traditionally be dedicated to one column or row now handles composite signals containing information from multiple columns or rows, reducing the total number of ADCs needed.
3Speed
If additional ADCs are added to reduce scan times, then reading speed is improved, but size increases
Solution Approach 1:
The patent combines multiple column and row signals into single composite signals that can be processed by fewer ADCs. Specifically, column signals from multiple columns are combined into a single combined column signal, and row signals from multiple rows are combined into a single combined row signal, allowing one ADC to process what previously required multiple ADCs.
Solution Approach 2:
The patent makes a single ADC perform multiple functions by having it process both combined column signals and combined row signals. The same ADC that would traditionally be dedicated to one column or row now handles composite signals containing information from multiple columns or rows, reducing the total number of ADCs needed.
4Device complexity
If columns and rows are read one at a time in scanning fashion, then interface circuitry is simplified, but scan times increase with higher column/row counts
Solution Approach 1:
The patent combines multiple column and row signals into single composite signals that can be processed by fewer ADCs. Specifically, column signals from multiple columns are combined into a single combined column signal, and row signals from multiple rows are combined into a single combined row signal, allowing one ADC to process what previously required multiple ADCs.
Solution Approach 2:
The patent applies excitation signals at different frequencies to different columns and rows, allowing periodic sampling and frequency-domain analysis to separate the combined signals. This periodic excitation approach enables simultaneous reading of multiple columns and rows while using a single ADC through frequency multiplexing.
Data Source
AI summary
A technique for reading the columns (12) and rows (14) of a touch sensor (10) provides several advantages, including scalability to touch sensors with high column/row counts. A simultaneously applied set of column input signals (24) yields a corresponding set of column output signals (34) that are combined into a combined column signal (38) that is transformed into the frequency domain after digitization, to yield column values (48) corresponding to the respective touch sensor columns (12). The same process applied with respect to the touch sensor rows (14) yields a set of row values (50), with evaluation of the frequency-domain column and row values (48, 50) providing the basis for detecting touch inputs to the touch sensor (10).