Touch Sensing Circuit Using GM Conversion to Cut Chip Area
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Solution Overview
Problem
Existing touch sensing systems face challenges in reducing chip area and power consumption while maintaining sensitivity, accuracy, and noise immunity.
Innovation Solution
The proposed touch sensing system incorporates a detected capacitor Cm with a transmitting and receiving electrode arrangement, connected to a modulation module via a GM module. This system converts charge transferred to the receiving electrode into a current, which is then integrated and modulated to obtain an output parameter characterizing the detected capacitor Cm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a larger integration capacitance is used to increase bandwidth, then the bandwidth of the integrator is improved, but the chip area and power consumption increase
Solution Approach 1:
The patent changes the operating parameters of the integrator by using a smaller integration capacitance value while adjusting the feedback mechanism through the GM module and comparator to maintain the required bandwidth performance, thus reducing chip area without sacrificing speed
2Speed
If a larger integration capacitance is used to increase bandwidth, then the bandwidth of the integrator is improved, but the power consumption increases
Solution Approach 1:
The patent optimizes the power consumption by using a smaller integration capacitance and adjusting the feedback current through the GM module to achieve the required bandwidth with lower power expenditure
3Measurement precision
If one ADC is used for each sensing channel, then the measurement precision is improved, but the chip area and power consumption increase
Solution Approach 1:
The patent merges multiple ADC functions into a single ADC by using the GM module to convert charge from multiple sensing channels into current signals that can be sequentially processed, thus reducing chip area while maintaining measurement precision through time-multiplexed conversion
4Measurement precision
If one ADC is used for each sensing channel, then the measurement precision is improved, but the power consumption increases
Solution Approach 1:
The patent combines multiple ADC operations into a single ADC resource that serves multiple sensing channels through time-multiplexed operation, reducing total power consumption while maintaining the precision required for accurate touch sensing measurements
5Area of stationary object
If one ADC is multiplexed for multiple channels, then the chip area is reduced, but the device complexity and control complexity increase
Solution Approach 1:
The patent introduces the GM module as an intermediary that converts charge from multiple sensing channels into current signals, simplifying the control of the multiplexed ADC by providing standardized current inputs that are easier to manage than direct charge measurements from multiple channels
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 achieves high sensitivity, accuracy, and noise immunity with reduced chip area and power consumption, simplifying circuit design and improving signal-to-noise ratio through amplitude and phase modulation.
Implementation Method 1
The GM module converts a charge transferred to the receiving electrode into a current and outputs same to the modulation module
Implementation Method 2
integrates and stores same on the integrating capacitor C1
Implementation Method 3
a negative input terminal of the comparator CMP is connected to a reference voltage Vref, and an output signal of the comparator CMP is used for controlling the turning off or disconnecting of the switch SW1 and the switch SW3
Data Source
AI summary
Disclosed is a touch sensing system, including a detected capacitor Cm. A transmitting electrode and a receiving electrode of a sensor are arranged at two ends of the detected capacitor Cm, and one end of the detected capacitor Cm corresponding to the receiving electrode is connected to a modulation module via a GM module. An excitation signal is input from the transmitting electrode. The GM module converts a charge transferred to the receiving electrode into a current and outputs same to the modulation module, and the modulation module performs integration and modulation according to the current to obtain an output parameter characterizing the detected capacitor Cm. Provided is a touch sensing system to reduce chip area and power consumption and improve the reliability of touch sensing.