Front-End Signal Compensation for Touch Surface Sensitivity
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Solution Overview
Problem
Conventional touch surface devices amplify both dynamic and static portions of output signals, leading to poor sensitivity and inefficient utilization of the amplifier's dynamic range, and large feedback capacitors increase IC chip size and cost.
Innovation Solution
Compensating the output signal before amplification by generating a compensation signal with a specific amplitude, waveform, frequency, and phase, using a look-up table, digital-to-analog converter, and compensation capacitor or current converter, to isolate the dynamic portion of the signal, thereby reducing the size and cost of feedback capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplifier amplifies both dynamic and static portions of the output signal, then the amplifier provides complete signal amplification, but the sensitivity is poor and the dynamic range utilization is inefficient
Solution Approach 1:
The patent extracts and removes the static portion of the output signal before amplification using a compensation circuit. This allows the amplifier to focus solely on amplifying the dynamic signal portion, thereby improving sensitivity and dynamic range utilization without requiring complex post-amplification processing to separate the static component.
Solution Approach 2:
The patent applies preliminary compensation to remove the static signal portion before the amplification stage. By performing this signal conditioning action in advance, the system optimizes the amplifier's performance and avoids the need for complex processing after amplification, resolving the contradiction between sensitivity and processing complexity.
2Reliability
If a large feedback capacitor is used to accommodate large charge amplitudes, then the signal-to-noise ratio is sufficiently high, but the IC chip size and cost increase significantly
Solution Approach 1:
The patent extracts and removes the large static charge amplitude through compensation before amplification. This allows the use of a much smaller feedback capacitor in the amplifier, since the capacitor only needs to handle the reduced dynamic signal portion rather than the full large charge amplitude, thereby reducing IC chip area while maintaining adequate signal-to-noise ratio.
Solution Approach 2:
The patent changes the parameter of charge amplitude by removing the static portion through compensation. This parameter change enables the use of a smaller feedback capacitor value, which directly reduces the IC chip area required while preserving the necessary signal-to-noise performance for reliable operation.
Data Source
AI summary
A touch surface device having improved sensitivity and dynamic range is disclosed. In one embodiment, the touch surface device includes a touch-sensitive panel having at least one sense node for providing an output signal indicative of a touch or no-touch condition on the panel; a compensation circuit, coupled to the at least one sense node, for generating a compensation signal that when summed with the output signal removes an undesired portion of the output signal so as to generated a compensated output signal; and an amplifier having an inverting input coupled to the output of the compensation circuit and a non-inverting input coupled to a known reference voltage.