Reset-Mode Integrating Amplifier for Faster Capacitive Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional capacitance sensing systems for touchscreens require complex and costly circuits due to the use of two large integration capacitors, leading to increased circuit size and complexity.
Innovation Solution
The implementation of an integrating amplifier with a high slew rate and bandwidth in RESET mode, achieved by decreasing the compensating capacitor and increasing the output stage current, using diode connected devices and compensating capacitors in parallel, to enhance stability and reduce circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two large integration capacitors are used in parallel with a switched capacitor integrator, then capacitance sensing accuracy is improved, but circuit complexity and circuit size increase
Solution Approach 1:
The patent extracts the reset function from a separate physical capacitor and implements it through a switch connected to ground. This removes the need for the second large capacitor while maintaining the reset capability, thereby reducing circuit complexity and component count while preserving measurement precision
Solution Approach 2:
The patent merges the reset function with the existing integration capacitor by using a switch to connect the capacitor to ground. This combines the integration and reset functions into a single capacitor structure, eliminating the need for separate capacitors and reducing overall circuit complexity
2Measurement precision
If two large integration capacitors are used in parallel with a switched capacitor integrator, then capacitance sensing accuracy is improved, but circuit size increases
Solution Approach 1:
The patent extracts the reset function from a separate physical capacitor and implements it through a switch connected to ground. This removes the need for the second large capacitor while maintaining the reset capability, thereby reducing circuit size while preserving measurement precision
Solution Approach 2:
The patent merges the reset function with the existing integration capacitor by using a switch to connect the capacitor to ground. This combines the integration and reset functions into a single capacitor structure, eliminating the need for separate capacitors and reducing overall circuit size
3Speed
If the compensating capacitor is decreased and output stage current is increased, then slew rate and bandwidth are improved, but power consumption increases
Solution Approach 1:
The patent dynamically adjusts the compensating capacitor value based on operating conditions. By using a switch to connect or disconnect the compensating capacitor, the circuit can optimize between slew rate (when capacitor is connected) and power consumption (when capacitor is disconnected), allowing adaptive performance tuning
Solution Approach 2:
The patent changes the compensating capacitor parameter dynamically through switching. This allows the circuit to adjust its electrical characteristics in real-time, optimizing the balance between slew rate and power consumption based on operational requirements
Data Source
AI summary
Embodiments of a capacitance sensing system including an integrating amplifier and methods for operating the same to provide a higher slew rate and bandwidth are described. In one embodiment, the integrating amplifier comprises an input stage including an inverting input coupled to an electrode of a capacitor to sense a capacitance and a non-inverting input coupled to a reference potential, and an output stage including a compensating capacitor coupled to an output. The compensating capacitor comprises two smaller capacitors coupled in parallel and a switching element configured to open when the integrating amplifier is operated in a RESET mode decoupling one of the two smaller capacitors from the output to decrease capacitance of the compensating capacitor.