Capacitive Touch ADC Circuit for Low-Power Multi-Channel Sensing
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Solution Overview
Problem
Existing touch-based user interfaces in smart cards face challenges with high power consumption, low sensitivity, and limited applicability to multi-channel touch sensors due to the size constraints of sample-and-hold capacitors, which hinder accurate and efficient touch event detection.
Innovation Solution
The electronic device incorporates a configuration of capacitors and an analog-to-digital converter, where additional capacitors are used to maintain voltage within optimal conversion ranges, enabling efficient touch position capturing and reducing power consumption, while supporting multi-channel touch sensors through a set of switchably coupled capacitors and GPIO pins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional touch-based user interfaces are implemented in smart cards, then touch event detection capability is provided, but power consumption increases and sensitivity decreases
Solution Approach 1:
The touch sensor is divided into multiple independent channels, each with its own capacitor configuration. This allows selective activation of only the necessary channels, reducing overall power consumption while maintaining detection sensitivity in active regions
Solution Approach 2:
The patent dynamically adjusts capacitor connections and switching configurations based on touch detection requirements. By changing the electrical parameters (capacitance values, switching states) adaptively, the system optimizes the balance between sensitivity and power consumption for different operating conditions
2Measurement precision
If sample-and-hold capacitors are enlarged to improve conversion accuracy, then measurement precision improves, but device area increases
Solution Approach 1:
Multiple capacitors are arranged in a nested or shared configuration where capacitors serve multiple functions across different channels. The third capacitor is shared between multiple first capacitors, allowing accurate measurements without proportionally increasing total capacitor area
Solution Approach 2:
The third capacitor serves multiple purposes: it is coupled to multiple first capacitors and can be switchably connected to different channels. This multi-functional design allows a single capacitor to support multiple measurement channels, reducing the total area required compared to dedicated capacitors for each channel
3Adaptability or versatility
If multiple capacitors are added to support multi-channel touch sensors, then adaptability improves, but device complexity increases
Solution Approach 1:
The third capacitor is designed as a universal component that can be switchably connected to multiple first capacitors and second capacitors. This single multi-functional capacitor enables multi-channel support without requiring a separate capacitor for each channel, thereby limiting the increase in device complexity
Solution Approach 2:
The third capacitor acts as an intermediary element that mediates between multiple first capacitors and second capacitors. By introducing this intermediate switching capacitor, the system achieves multi-channel adaptability while managing complexity through a centralized switching mechanism rather than complex direct connections between all components
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 configuration allows for accurate and low-power touch event detection, enabling the use of multi-channel touch sensors and reducing noise, thereby enhancing the sensitivity and efficiency of touch-based user interfaces in smart cards.
Implementation Method 1
the capacitor is configured to measure changes in a capacitance value, in particular to measure changes in a self-capacitance value or mutual capacitance value in response to a touch event
Data Source
AI summary
According to a first aspect of the present disclosure, an electronic device for use in a touch-based user interface is provided, the electronic device comprising a first capacitor, a second capacitor, a third capacitor, and an analog-to-digital converter, wherein: the first capacitor and the second capacitor are switchably coupled to each other; the first capacitor is switchably coupled to an input of the analog-to-digital converter; the second capacitor is coupled to the input of the analog-to-digital converter; the third capacitor is coupled to the first capacitor; the third capacitor is switchably coupled to the second capacitor; the third capacitor is switchably coupled to the input of the analog-to-digital converter. According to a second aspect of the present disclosure, a corresponding method of manufacturing an electronic device for use in a touch-based user interface is conceived.