Analog Front-End Circuit Noise Isolation for Touch Controllers
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Solution Overview
Problem
Conventional analog front-end circuits for touch controllers suffer from signal distortion due to coupling noise signals from display panels, which affect the signal-to-noise ratio and render them ineffective for accurate touch sensing.
Innovation Solution
The proposed analog front-end circuit incorporates a first and second switch to control the reception of touch driving signals and coupling noise signals, where the second switch is turned on to transmit noise signals to a reference voltage during a specific period, and the first switch is turned on during a non-overlapping period to receive the touch driving signal, thereby isolating noise from the touch signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the amplifier receives both touch signal and reference voltage through conventional analog front-end circuit, then the output signal is generated, but coupling noise signals from display panel cause signal distortion
Solution Approach 1:
The patent segments the signal reception process into two distinct time periods: a first period for receiving touch signals through the inverting input terminal, and a second period for receiving reference voltage through the non-inverting input terminal. This temporal segmentation prevents coupling noise from the display panel from interfering with touch signal reception, as the amplifier only receives one type of signal at a time based on the timing of switch operations.
Solution Approach 2:
The patent implements periodic switching between two operational modes: during the first period, the first switch is turned on to connect the touch signal to the amplifier while the second switch is off; during the second period, the second switch is turned on to connect the reference voltage while the first switch is off. This periodic action ensures that coupling noise signals do not interfere with touch signal processing, as the amplifier receives reference voltage during the period when display panel noise is present.
2Productivity
If the amplifier continuously receives signals from both input terminals, then the circuit operates continuously, but noise interference reduces measurement accuracy
Solution Approach 1:
The patent makes the amplifier's input configuration dynamic by using two switches that are controlled to change states periodically. The first switch connects the inverting input terminal to the touch signal during the first period, while the second switch connects the non-inverting input terminal to the reference voltage during the second period. This dynamic switching allows the circuit to adapt its configuration based on the operational phase, maintaining continuous operation while ensuring high measurement precision during touch signal reception.
Data Source
AI summary
An analog front-end circuit for a touch controller and an operating method thereof are provided. The analog front-end circuit includes an analog front-end, a first switch and a second switch. The analog front-end includes an input terminal and an output terminal. The first switch includes a first terminal and a second terminal. The first terminal of the first switch is coupled to the input terminal of the analog front-end, and the second terminal of the first switch is coupled to a panel routing. The second switch includes a first terminal and a second terminal. The first terminal of the second switch is coupled to the second terminal of the first switch, and the second terminal of the second switch is coupled to a reference voltage.