Tertiary CDS Sampling for Noise-Immune Capacitance Sensing
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Solution Overview
Problem
Capacitive touch controllers face challenges in accurately sensing capacitance changes due to noise interference from external environments, which affects the reliability of touch inputs.
Innovation Solution
A semiconductor device and system employing tertiary correlated double sampling (CDS) to reduce noise immunity by sampling noise at multiple points, canceling offsets, and using high-pass filtering and low-pass filtering to enhance signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional dual sampling is used, then the circuit complexity is low, but the noise immunity is insufficient
Solution Approach 1:
The patent segments the noise sampling process into three distinct sampling operations (first sampling at time t1, second sampling at time t2, third sampling at time t3) rather than using traditional dual sampling. This segmentation allows the system to capture noise characteristics at multiple discrete points, enabling more effective noise cancellation while maintaining circuit simplicity through the use of existing amplifier and switch components.
Solution Approach 2:
The patent implements periodic sampling actions at three different time points (t1, t2, t3) within a driving signal cycle, where each sampling operation captures noise at a specific phase. This periodic multi-point sampling approach enhances noise immunity by providing multiple noise measurements that can be processed to eliminate periodic noise components while keeping the circuit structure relatively simple.
2Reliability
If multiple sampling points are used, then the noise immunity increases, but the sampling complexity increases
Solution Approach 1:
The patent makes the existing amplifier and switch components multi-functional by using them for both signal amplification and for performing three distinct sampling operations. The same amplifier circuit that amplifies the driving signal also serves to sample noise at three different time points, eliminating the need for separate dedicated sampling circuits and thereby reducing overall sampling complexity while achieving enhanced noise immunity.
3Reliability
If high-pass filtering is applied, then the low-frequency noise is reduced, but the signal processing complexity increases
Solution Approach 1:
The patent merges the high-pass filtering function with the existing amplifier and capacitor circuitry. The capacitor in the amplifier circuit naturally provides high-pass filtering characteristics when combined with the resistive elements, allowing low-frequency noise reduction to be achieved through the inherent properties of the existing components rather than requiring a separate dedicated high-pass filter circuit, thus minimizing additional signal processing complexity.
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 effectively increases noise immunity, improving the accuracy of capacitance sensing and enhancing the operating range of capacitive touch controllers by reducing low-frequency noise and amplifying driving signals.
Implementation Method 1
The noise is high-pass filtered through the first resistor and the first capacitor
Implementation Method 2
an amplifier that receives noise and a driving signal, resets for each predetermined period of the driving signal, and samples the noise
Implementation Method 3
A sampler performs second sampling and third sampling on the first sampled noise
Implementation Method 4
The third sub-sampler receives outputs of the first and second integrators and performs a subtracting operation
Data Source
AI summary
Provided are a semiconductor device and a semiconductor system, which can increase immunity against noises through tertiary correlated double sampling (CDS). The semiconductor device includes an amplifier that receives noise and a driving signal, resets for each predetermined period of the driving signal and samples the noise to generate first sampled noise. The first sampled noise includes multiple noise differences each occurring between consecutive reset points. A sampler performs second sampling and third sampling on the first sampled noise and performs fourth sampling on the second and third sampled noises. The first sampled noise includes first to third noise differences, the second sampled noise is a difference between the first and second noise differences, the third sampled noise is a difference between the second and third noise differences, and the fourth sampled noise is a difference between the second and third sampled noises.