Attenuator Circuit for Capacitance Sensing Noise Saturation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitance sensing systems face saturation issues due to high amplitude noise, which can block touchscreen controller operation and prevent accurate detection of touch events.
Innovation Solution
The implementation of an attenuator circuit within the capacitance-sensing system, which includes a charge-balanced converter and current mirror based solid-state attenuator, helps maintain the converter in a linear operation range by reducing noise amplitude and providing zero differential voltage across resistive dividers, allowing for precise detection of touch locations and types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high amplitude noise is present in the capacitance sensing system, then the converter may operate in saturation mode, but this blocks accurate detection of touch events
Solution Approach 1:
An attenuator circuit is introduced as an intermediary component between the capacitance sensing system and the converter. This attenuator reduces the amplitude of noise signals before they reach the converter, preventing saturation while preserving the integrity of touch event signals for accurate detection.
2Measurement precision
If the converter operates in saturation mode due to high noise amplitude, then the system cannot accurately detect touch locations, but reducing noise amplitude is needed to maintain linear operation range
Solution Approach 1:
The attenuator circuit serves as a mediator that selectively reduces noise amplitude while preserving touch signal characteristics. By positioning the attenuator in the signal path before the converter, it filters harmful high-amplitude noise without compromising the precision of touch location detection.
3Reliability
If active stylus is used which generates high noise, then the touchscreen controller may saturate, but the attenuator circuit enables reliable operation by preventing saturation
Solution Approach 1:
The attenuator circuit converts the harmful effect of high-amplitude noise from active stylus into a manageable signal level. By reducing the noise amplitude to within the linear operation range of the converter, the system can reliably detect stylus inputs without saturation, transforming a potential failure mode into reliable operation.
Data Source
AI summary
Apparatuses and methods of input attenuator circuits are described. One sensing circuit includes an attenuator circuit to receive a signal from an electrode of a sense array. The attenuator circuit is configured to attenuate input current of the signal. The attenuator circuit includes an attenuation matrix including an input terminal to receive the signal and multiple resistors. The attenuation matrix is configured to split the input current into an output current of the attenuation signal on a first output terminal and a second output current on a second output terminal. The attenuation matrix is to output the attenuated signal on the first output terminal to an integrator of the sensing circuit. The attenuator circuit also includes a buffer coupled between the attenuation matrix and the integrator. The buffer is configured to maintain a substantially same voltage at the first output terminal and the second output terminal.