Single-Line Drive Sense Circuit for Noise-Resistant Touch Sensing
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Solution Overview
Problem
Conventional digital signal sensing technologies face challenges such as separate lines for drive and sense signals, susceptibility to noise, limited resolution and refresh rates, difficulty in sensing long electrodes, and high power consumption, especially for touch screen applications.
Innovation Solution
The implementation of a drive sense circuit with an analog front end (AFE) that uses a single line for concurrent drive and sense operations, employing an analog sinusoidal current drive signal based on an analog sinusoidal voltage reference to improve noise immunity and reduce power consumption, while enabling full screen touch sensing concurrent with video display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate lines are used for drive and sense signals, then signal integrity is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent combines drive and sense operations into a single shared line, eliminating the need for separate dedicated lines. The system multiplexes the single line to perform both drive and sense functions sequentially, reducing circuit complexity while maintaining signal integrity through careful timing and impedance management.
Solution Approach 2:
The single line serves multiple functions by alternating between drive and sense modes. The same physical connection is used for both driving the electrode and sensing its impedance, making the line universal rather than dedicated to a single function, thereby reducing overall circuit complexity.
2Measurement precision
If separate lines are used for drive and sense signals, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent merges drive and sense operations into a single shared line, reducing the total number of active signal paths. This consolidation reduces overall power consumption while maintaining measurement precision through sequential operation and proper impedance matching during sense phases.
3Ease of operation
If digital signal sensing is used, then ease of processing is improved, but noise immunity deteriorates
Solution Approach 1:
The system uses periodic sinusoidal drive signals at specific frequencies to excite the electrode. By operating at defined frequencies and using synchronous detection, the system achieves both noise immunity through frequency selectivity and ease of processing through regular periodic waveforms that simplify detection algorithms.
4Device complexity
If conventional sensing methods are used, then device simplicity is maintained, but the ability to sense long electrodes deteriorates
Solution Approach 1:
The use of periodic sinusoidal signals enables the system to drive and sense long electrodes effectively. The continuous periodic excitation maintains signal integrity over long distances, and the frequency-based approach allows for better signal-to-noise ratio compared to conventional DC or pulsed methods, extending the usable electrode length.
5Productivity
If high refresh rates are implemented, then productivity is improved, but power consumption increases
Solution Approach 1:
By merging drive and sense operations into a single multiplexed line, the system reduces the total switching activity and signal generation requirements. This consolidation allows for high refresh rates to be achieved with lower power consumption compared to systems using separate dedicated lines for each function.
Data Source
AI summary
A drive sense circuit (DSC) includes an analog front end (AFE) circuit, a filter circuit, and a data processing circuit. The AFE circuit includes a signal source circuit and a comparison circuit. The signal source circuit, when enabled and coupled to a sensor, provides an analog drive signal to the sensor, which affects an electrical property of the analog drive signal. The comparison circuit compares the analog drive signal as effected by the sensor to a reference signal and produces an analog sensed signal that represents the effected electrical property of the analog drive signal. The filter filters the analog sensed signal to produce a filtered sensed signal. The data processing circuit operably generates a digital value representative of sensed characteristic of the sensor based on the filtered sensed signal.