Differential Sampling Circuit Using Common-Mode Charge Redistribution
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Solution Overview
Problem
Differential sampling circuits face challenges in processing signals with significantly smaller voltage differences, which can lead to issues in subsequent processing circuits due to low voltage differences being far smaller than the absolute values of the signals, causing problems such as ground fluctuations and undefined sampling times.
Innovation Solution
A sampling circuit that includes a common-mode signal generating circuit and a switching circuit, which couples the sampling capacitors to a common-mode signal in the redistribution phase, allowing for effective processing of signals with small voltage differences by generating a common-mode component of the input signals and using it to charge the capacitors, thereby avoiding issues with conventional approaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional differential sampling circuits are used to sample signals with small voltage differences, then the absolute voltage values are captured, but the differential quantity becomes lost due to ground fluctuations and undefined sampling times
Solution Approach 1:
The patent introduces a common-mode signal as an intermediary reference voltage during the redistribution phase. This common-mode signal serves as a stable mediator that both sampling capacitors reference simultaneously, eliminating ground fluctuations and providing a well-defined sampling time reference for accurate differential voltage measurement
Solution Approach 2:
The patent connects both sampling capacitors to the same common-mode signal voltage level during redistribution, creating an equipotential reference state. This ensures both capacitors experience identical reference conditions, eliminating differential errors caused by ground potential variations and enabling precise differential measurement
2Device complexity
If the sampling capacitors are connected to ground in the redistribution phase, then the circuit is simple to implement, but cross-talk and power loss increase due to ground fluctuations
Solution Approach 1:
The patent changes the reference voltage parameter from ground (0V) to a dynamic common-mode signal that tracks the average of the input signals. This parameter change eliminates cross-talk and power loss by ensuring both capacitors reference the same time-varying voltage level, preventing differential errors while maintaining circuit simplicity
3Adaptability or versatility
If the sampling capacitors are connected to different reference voltages, then each capacitor can be optimized independently, but the differential measurement becomes inaccurate due to reference voltage differences
Solution Approach 1:
The patent enforces equipotentiality by connecting both sampling capacitors to the identical common-mode signal during redistribution. This ensures both capacitors operate under the same reference conditions, eliminating differential measurement errors while allowing individual capacitor optimization for other parameters such as capacitance value and physical layout
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
This solution enables robust processing of signals with small voltage differences, reducing cross-talk and power loss, and ensuring accurate sampling by using the common-mode signal in the redistribution phase, thus addressing the limitations of conventional methods.
Implementation Method 1
a first sampling capacitor; a second sampling capacitor
Data Source
AI summary
Sampling circuits and methods for sampling are provided. In a first operating phase, sampling capacitors are coupled to inputs, and in a second operating phase, to a common-mode signal.