Dynamic ADC Resolution for Touchscreen RF Noise
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Solution Overview
Problem
Capacitive touchscreen systems face significant power consumption issues due to the need for high precision analog-to-digital converters (ADCs) to handle RF noise, which is not always present, leading to inefficiencies in battery life for mobile devices.
Innovation Solution
A capacitive touchscreen system with an ADC that can switch between high and low resolution modes based on detected RF noise conditions, reducing power consumption when precision is not required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high precision ADC is used to handle RF noise, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The ADC resolution is made dynamically adjustable based on detected RF noise conditions. The system transitions from a static fixed-resolution ADC to a dynamic ADC that adapts its resolution level (e.g., 12-bit vs 9-bit) according to the operational environment, allowing high precision when needed and low power consumption when not required.
Solution Approach 2:
The patent changes the resolution parameter of the ADC based on environmental conditions. When RF noise is detected, the system switches to higher resolution mode; when noise levels are low, it operates in lower resolution mode. This parameter adaptation resolves the contradiction between precision and power consumption by making the precision level variable rather than fixed.
2Measurement precision
If high precision ADC is used continuously, then measurement precision is maintained, but battery life decreases
Solution Approach 1:
The system periodically monitors RF noise conditions and adjusts ADC resolution accordingly. Instead of maintaining high precision continuously, the system uses high precision only during periods when RF noise is present, and switches to low precision during quiet periods, thereby extending battery life while maintaining precision when needed.
Solution Approach 2:
The ADC resolution is dynamically adjusted based on real-time noise detection. The system transitions between high and low resolution modes depending on environmental conditions, optimizing the balance between measurement precision and battery life by avoiding unnecessary high-power operation during low-noise periods.
3Reliability
If digital filters are applied to handle RF noise, then signal quality is improved, but precision loss occurs
Solution Approach 1:
The patent introduces an intermediary approach by using a programmable ADC that can adjust its resolution level as a mediator between the raw sensor signal and the digital filter processing. By setting the ADC resolution dynamically, the system optimizes the input signal quality for subsequent digital filtering operations, reducing precision loss that would occur with fixed high-resolution ADC followed by aggressive filtering.
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 effectively manages power consumption by adjusting ADC resolution in response to noise levels, optimizing battery life in varying environmental conditions.
Implementation Method 1
mutual capacitances existing between the first and second pluralities of electrodes at locations where the first and second pluralities of electrodes intersect, the mutual capacitances changing in the presence of one or more fingers of a user or touch devices brought into proximity thereto
Data Source
AI summary
Various embodiments of a low-power-consumption analog-to-digital converter (“ADC”) for a touchscreen or touch panel in a capacitive sensing system are disclosed. The ADC is configured to operate in a first mode or a second mode. The first mode is characterized by a first resolution having a first number of ADC bits and a first level of power consumption associated therewith. The second mode is characterized by a second resolution having a second number of bits and a second level of power consumption associated therewith. The ADC operates under control of the controller and is configured such that the first number of bits is greater than the second number of bits and the first power level is greater than the second power level. The controller causes the ADC to switch from operating in the first mode to operating in the second mode when low radio frequency (RF) noise conditions are detected by sense circuitry, the ADC and/or the controller.