SAR ADC Overvoltage Detection Using Successive Approximation
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Solution Overview
Problem
Conventional SAR ADC circuitry faces issues with overvoltage detection, requiring additional analogue or digital circuitry and experiencing high delays, which can lead to damage and saturation.
Innovation Solution
The ADC circuitry employs successive approximation operations to determine if the input voltage magnitude is outside its full-scale range by analyzing comparison results, allowing for early detection of overvoltage without additional circuitry, and includes overvoltage circuitry to attenuate or isolate the input signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional overvoltage detection methods (diode detector-comparator or checking final digital approximation) are used, then overvoltage can be detected, but additional circuitry is required and detection delay is high
Solution Approach 1:
The SAR ADC circuitry performs overvoltage detection using its own existing comparator and successive approximation operations without requiring external detection circuits. The system uses its inherent digital approximation capability to simultaneously perform both ADC conversion and overvoltage detection functions
Solution Approach 2:
The SAR circuitry is designed to perform multiple functions: it conducts the primary ADC conversion process and simultaneously performs overvoltage detection by analyzing comparison results during the approximation operations, eliminating the need for separate detection circuitry
2Reliability
If conventional overvoltage detection methods are used, then overvoltage can be detected, but detection delay is high causing damage and saturation
Solution Approach 1:
The overvoltage detection is performed during the successive approximation operations before the ADC conversion is complete. By checking comparison results at intermediate stages (particularly at the middle bit and least significant bit), the system detects overvoltage conditions early in the conversion process rather than waiting for the final result
Solution Approach 2:
When an overvoltage condition is detected during the approximation operations, the SAR circuitry can skip completing the remaining conversion steps and immediately output an overvoltage indication, significantly reducing the time to detect and respond to overvoltage conditions
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 method enables fast and efficient overvoltage detection, protecting the ADC from damage and ensuring continuous conversion without saturation, using minimal additional circuitry.
Implementation Method 1
a comparator having first and second comparator-input terminals and operable to generate a comparison result based on a potential difference applied across those terminals
Data Source
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Figure 3A~3B
AI summary
Analogue-to-digital converter, ADC, circuitry, comprising: an analogue input terminal, operable to receive an analogue input voltage signal; a comparator having first and second comparator-input terminals and operable to generate a comparison result based on a potential difference applied across those terminals; and successive-approximation control circuitry configured to apply a potential difference across the first and second comparator-input terminals based upon the input voltage signal, and configured to control the potential difference for each of a series of successive approximation operations to cause the comparator to test in each successive approximation operation whether a magnitude of the analogue input voltage signal is bigger or smaller than a corresponding test value, the test value for each successive approximation operation being, dependent on a comparison result generated by the comparator in the preceding approximation operation, bigger or smaller than the test value for the preceding approximation operation by a difference amount configured for that successive approximation operation, the successive approximation operations configured such that the test value for a target one of the successive approximation operations between two other successive approximation operations of the successive approximation operations is, dependent on the comparison result generated by the comparator in each preceding approximation operation, an overvoltage test value whose magnitude is equal to or greater than a magnitude of a full-scale value defining a boundary of a full-scale range of the ADC circuitry, wherein the successive-approximation control circuitry is configured, before carrying out all of the successive approximation operations, to: determine, based on a combination of the comparison results of the target successive approximation operation and at least one preceding approximation operation, if the comparison result of the target successive approximation operation indicates that the magnitude of the analogue input voltage signal is outside said full-scale range.