Successive Approximation ADC with Multi-Cycle Step Selection
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Solution Overview
Problem
Conventional successive approximation analog to digital converters (SA-ADCs) are slow and consume high power due to the need for multiple comparisons and long recursion cycles, which limits the speed of analog to digital conversion and increases circuit area and power consumption.
Innovation Solution
The proposed circuit improves convergence by using multiple comparator output signals from preceding recursion cycles to select successive steps in digital reference values, allowing for faster narrowing of the range of possible analog input signal values without increasing recursion cycle duration, thereby reducing the number of steps required for conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional middle-value comparison method is used, then the conversion process is simple to implement, but the conversion speed is slow
Solution Approach 1:
The patent applies preliminary action by using comparator output signals from preceding recursion cycles to pre-determine the direction of step selection. The control circuit uses historical comparison results to anticipate whether the next digital reference value should increase or decrease, allowing the system to proactively move toward the correct value rather than reactively adjusting after each comparison. This reduces the number of recursion cycles needed for convergence.
Solution Approach 2:
The patent implements feedback by continuously utilizing comparator output signals from multiple preceding recursion cycles to dynamically adjust the selection of successive steps. The control circuit feeds back historical comparison information to optimize the convergence path, selecting steps based on patterns in previous comparator outputs. This feedback mechanism accelerates convergence while maintaining circuit simplicity.
2Measurement precision
If more recursion cycles are performed to improve accuracy, then the measurement precision increases, but the power consumption increases
Solution Approach 1:
The patent applies dynamics by making the recursion cycle duration adaptive rather than fixed. The control circuit dynamically adjusts the number of recursion cycles based on real-time comparator output signals, terminating the conversion process as soon as the desired accuracy is achieved. This dynamic adaptation allows the system to consume less power for simple conversions while maintaining high precision when needed, optimizing the trade-off between accuracy and power consumption.
3Measurement precision
If the recursion cycle duration is extended to allow proper settling, then the measurement accuracy improves, but the conversion speed decreases
Solution Approach 1:
The patent uses preliminary action by incorporating comparator output signals from preceding recursion cycles into the step selection process. This allows the system to anticipate the required adjustment direction before the current comparison completes, reducing the settling time needed while maintaining accuracy. The control circuit prepares the next step based on historical data, so less time is required for each individual comparison to achieve the same overall precision.
Solution Approach 2:
The patent maintains continuity of useful action by overlapping the utilization of comparator outputs across multiple recursion cycles. Instead of waiting for each comparison to fully settle before initiating the next step, the system continuously processes comparator outputs from preceding cycles to guide step selection. This continuous utilization of comparison information reduces idle settling time and maintains high conversion speed without sacrificing precision.
Data Source
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AI summary
During successive approximation analog to digital conversion a series of successive digital reference values is selected that converges towards a digital representation of an analog input signal. An analog reference signal is generated dependent on the successive digital reference values and compared to the analog input signal. The digital reference values are selected dependent on comparison results. In the selection of the digital reference values successive steps between digital reference values are each selected dependent on values of the comparator result from a plurality of preceding recursion cycles. The comparison results define a series of successively narrower ranges of digital values that contain a digital representation of the analog input signal. Use of a plurality of comparator results for selecting the steps in the digital reference values makes it possible to reduce uncertainty about whether the comparison result has settled. This in turn makes it possible to reduce the sizes of the successive ranges, which speeds up convergence.