Miller Capacitor ADC Switching to Limit Noise Propagation
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Solution Overview
Problem
Conventional analog to digital converters (ADCs) experience reliability issues due to noise propagation and capacitor failure, particularly when operating multiple ADCs, as noise generated during non-conversion periods can affect other ADCs through power supply or ground systems, and the longer operating time increases the likelihood of capacitor failure.
Innovation Solution
An ADC design that includes a differential amplifier circuit, an amplifying element, a counter, and a capacitor with a switch that disconnects the capacitor from the input/output terminals during non-conversion periods, reducing noise propagation and capacitor load, thereby enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the capacitor is connected in parallel with the amplification transistor to increase input-side capacitance, then noise generated in the ADC during conversion period is reduced, but noise generated during non-conversion period propagates to other ADCs via power supply or ground systems
Solution Approach 1:
The capacitor connection state is made dynamic rather than static. The switch controls the capacitor to be connected during conversion period and disconnected during non-conversion period, allowing the system to adapt its noise filtering characteristics to the operational phase, thus reducing noise propagation to other ADCs while maintaining noise reduction during conversion
Solution Approach 2:
The capacitor is periodically connected and disconnected based on the conversion period timing. During conversion period, the capacitor is connected to filter noise; during non-conversion period, it is disconnected to prevent noise propagation. This periodic switching aligns with the ADC operational cycles and resolves the contradiction between noise filtering and noise propagation
2Object-affected harmful factors
If the capacitor remains connected during operation, then noise filtering is maintained, but the charge/discharge time increases and capacitor failure probability increases
Solution Approach 1:
The capacitor is periodically connected only during conversion period and disconnected during non-conversion period. This reduces the total charge/discharge cycles and operating time of the capacitor, thereby decreasing wear and failure probability while maintaining noise filtering functionality when needed
Solution Approach 2:
The capacitor connection is dynamically controlled based on operational requirements. The switch enables the capacitor to be connected only when noise filtering is necessary (during conversion) and disconnected when not needed, optimizing both noise filtering performance and capacitor reliability by minimizing unnecessary operation
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 reduces noise propagation and decreases the likelihood of capacitor failure, improving the overall reliability of the ADC by disconnecting the capacitor during non-conversion periods, thus enhancing the ADC's performance and longevity.
Implementation Method 1
By connecting the capacitor and the amplification transistor in parallel, capacitance of the amplifier circuit as seen from an input side may be made larger than capacitance of the capacitor. This effect is referred to as a Miller effect.
Data Source
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AI summary
Reliability of an analog to digital converter provided with a capacitor is improved. A differential amplifier circuit amplifies a difference between an input analog signal and a ramp signal which changes over time and outputs the same as a difference signal. The amplifying element amplifies the difference signal and outputs the same as an amplified signal. A time measuring unit measures a length of a conversion period until a level of the analog signal substantially coincides with a level of the ramp signal on the basis of a level of the amplified signal and outputs the same as a digital signal obtained by converting the analog signal. One end of a capacitor is connected to one of an input terminal and a predetermined connection terminal of the amplifying element. A switch connects the other end of the capacitor to the other of the input terminal or the predetermined connection terminal in the conversion period, and disconnects the other end from the other in a period other than the conversion period.