Programmable ADC Sample-and-Hold Capacitance for Touch Resolution
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Solution Overview
Problem
Conventional capacitive touch systems face limitations in resolution due to sensor capacitance and parasitic capacitances, especially in high noise environments with large bulk capacitance, where the existing systems fail to provide sufficient detection accuracy.
Innovation Solution
A microcontroller-based system that includes an analog-to-digital converter (ADC) with a main sample and hold capacitor and additional programmable sample and hold capacitances, allowing for software-controlled adjustment of sample-and-hold capacitance to match sensor capacitance, thereby enhancing resolution through capacitive voltage division (CVD) method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fixed sample and hold capacitance is used, then device complexity is reduced, but measurement precision deteriorates in high noise environments with large bulk capacitance
Solution Approach 1:
The sample and hold capacitance is made dynamically adjustable through software control rather than being fixed. Multiple additional capacitances can be programmably coupled in parallel with the main capacitance to adjust the total capacitance value based on sensor requirements, enabling adaptation to different sensing conditions while maintaining manageable device complexity through modular design
Solution Approach 2:
The capacitance parameter of the sample and hold circuit is made variable through software control. The system can change the total capacitance value by programmably coupling additional capacitances in parallel, allowing optimization of measurement precision for different sensor types and environmental conditions without requiring complete redesign of the ADC architecture
2Measurement precision
If additional programmable capacitances are added to match large sensor capacitance, then measurement precision improves, but device complexity increases
Solution Approach 1:
The total sample and hold capacitance is segmented into a main capacitance and multiple additional programmable capacitances. This segmentation allows the system to build up the required total capacitance value in steps by selectively coupling additional capacitances, making the complexity manageable through modular architecture while achieving the precision needed for large sensor capacitance matching
Solution Approach 2:
The additional programmable capacitances serve multiple functions: they can be individually coupled or combined in parallel to create different total capacitance values, allowing the same hardware components to adapt to various sensor types and environmental conditions. This multi-functionality reduces the need for completely separate circuits for different sensing scenarios
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 system effectively increases the sample-and-hold capacitance to match large sensor capacitance, improving resolution and noise immunity by using programmable additional capacitances, allowing for precise detection of capacitance changes in capacitive touch sensors.
Implementation Method 1
a main sample and hold capacitor; and a plurality of additional sample and hold capacitances which can be programmably coupled in parallel with said main sample and hold capacitance
Implementation Method 2
One such application utilizes capacitive voltage division (CVD) to evaluate whether a capacitive touch element has been touched or not
Data Source
AI summary
An ADC module includes an analog to digital converter coupled with an analog bus, wherein the an analog to digital converter comprises a main sample and hold capacitor; and a plurality of additional sample and hold capacitances which can be programmably coupled in parallel with said main sample and hold capacitance.