Switched Capacitor Input Sensing for Compact Proximity Devices
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Solution Overview
Problem
Proximity sensor devices require large components like capacitors and resistors for input sensing, which increases their size, and as feature size decreases, the number of components increases further, necessitating a reduction in component size without compromising performance.
Innovation Solution
A processing system utilizing a switched capacitor configuration with an operational amplifier, feedback capacitor, and a switch that toggles between the feedback capacitor and a measurement circuit to perform oversampling, reducing the overall size while minimizing interference aliasing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large capacitors and resistors are used for input sensing in proximity sensor devices, then measurement precision is improved, but device size increases
Solution Approach 1:
The patent changes the capacitance value dynamically by switching between multiple capacitors (C1, C2, C3) with different capacitance values. The determination module selectively connects different capacitors to the sensing electrode based on the detected capacitance range, allowing the system to maintain high measurement precision across varying input conditions while using smaller individual capacitor components, thus reducing overall device size.
2Measurement precision
If the number of receiver components is increased to maintain sensing performance as feature size decreases, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The determination module serves multiple functions: it detects capacitance values, determines which capacitor to connect based on the detected value, and controls the switching of capacitors. This multi-functional design allows the system to maintain high sensing performance with fewer components, reducing device complexity while preserving measurement precision.
3Area of stationary object
If smaller capacitors are used to reduce device size, then device size is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent divides the capacitance sensing function into multiple segments by using several capacitors (C1, C2, C3) with different capacitance values. Each capacitor handles a specific range of capacitance measurements, allowing the system to use smaller individual capacitors while maintaining overall measurement precision through the segmented approach. The determination module coordinates which segment (capacitor) to use based on the input conditions.
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 solution reduces the size of the processing system while maintaining similar performance characteristics by using a switched capacitor for input sensing, allowing for smaller capacitors and fewer components, thus addressing the need for compactness in proximity sensor devices.
Implementation Method 1
a first capacitor coupled between the output and the inverting input to form a feedback path, and a second capacitor
Implementation Method 2
determine a capacitance measurement at the inverting input based on an amount of charge received by the second capacitor
Data Source
AI summary
Examples of the present disclosure generally relate to a switched capacitance technique for input sensing with an input device. A processing system includes an operational amplifier having a non-inverting input, an inverting input, and an output. The processing system further includes a first capacitor coupled between the output and the inverting input to form a feedback path, and a second capacitor. The processing system further includes a first switch coupled to the second capacitor. The first switch has a first state and a second state, where the first state couples the second capacitor to the first capacitor, and the second state couples the second capacitor to a measurement circuit. The processing system further includes a determination module coupled to the measurement circuit and configured to determine a capacitance measurement at the inverting input based on an amount of charge received by the second capacitor.