Multi-Controller Capacitive Sensing With Synchronized Scan Timing
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Solution Overview
Problem
Large capacitive sensing devices face challenges in control due to the finite number of connections a device controller has to signal lines, leading to difficulties in maintaining sensitivity and reducing noise from cross-coupling effects.
Innovation Solution
Implementing multiple device controllers connected to different portions of the capacitive sensors, with each controller including switching devices to control charging and discharging of drive and sense lines, and a common node or shield, synchronized to prevent overlapping charging and discharging events, and using shared reference capacitive sensors for capacitance comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single device controller is used to control a large capacitive sensing device, then the device complexity is reduced, but the measurement precision and sensitivity deteriorate due to the finite number of connections available to signal lines
Solution Approach 1:
The capacitive sensing device is divided into multiple zones, with each zone controlled by a separate device controller. Each controller manages a specific portion of the sensing device, allowing for more connections and signal lines per controller, thereby maintaining high measurement precision and touch sensitivity even in large-scale devices.
2Measurement precision
If multiple device controllers are used to control different portions of capacitive sensors, then the measurement precision and sensitivity are maintained, but the device complexity increases
Solution Approach 1:
Multiple device controllers are designed with identical or similar functional capabilities, each capable of controlling a portion of the capacitive sensing device independently. This multi-functionality allows the system to maintain high measurement precision across the entire device while distributing the control workload, thereby managing complexity through standardization.
3Productivity
If multiple controllers charge and discharge drive lines and sense lines independently, then the productivity and scanning speed are improved, but cross-coupling noise increases due to overlapping charging and discharging events
Solution Approach 1:
The charging and discharging operations of multiple device controllers are synchronized to occur in a periodic, non-overlapping sequence. Each controller operates in synchronized phases, ensuring that charging and discharging events do not overlap in time. This periodic coordination maintains high scanning speed while eliminating cross-coupling noise between controllers.
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 solution allows for scalable capacitive sensing systems, maintaining sensitivity and reducing noise, enabling effective force detection and touch interaction across larger surfaces while minimizing undesirable effects like cross-coupling noise.
Implementation Method 1
the capacitive sensors can be disposed, for example, in individual pixels or with intersecting drive and signal lines
Implementation Method 2
A capacitive sensing device can detect touch with a capacitive sensing device
Data Source
AI summary
A capacitive sensing device can include multiple capacitive sensors. A first device controller is operatively connected to a portion of the capacitive sensors, while a second device controller is operatively connected to another portion of capacitive sensors. A common node or shield can be connected between the first device controller and the second device controller. Charging and discharging events of selected drive lines in the capacitive sensing device and/or of the common node or shield can be synchronized to reduce undesirable effects such as noise and/or to prevent the charging events and the discharging events from overlapping with each other. One or more reference capacitive sensors can be shared by the multiple device controllers.