ADC Open Pin Detection via Sigma-Delta Modulator
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Solution Overview
Problem
Analog-to-digital converter (ADC) circuits in AC motor systems face challenges in detecting open pin conditions, which can lead to incorrect control signals and potential damage if not detected in real-time.
Innovation Solution
The implementation of a Sigma-Delta modulator, decimation filter, and open pin detection circuit within the ADC circuit, which converts analog signals to digital streams, and compares these streams to thresholds to indicate open pin conditions, allowing for real-time detection without affecting the normal operation of the ADC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ADC circuits are used without open pin detection, then the device complexity is reduced, but the reliability deteriorates due to undetected open pin conditions causing incorrect control signals
Solution Approach 1:
The open pin detection circuit is merged with the existing ADC circuit by sharing the Sigma-Delta modulator and decimation filter resources. The detection functionality is integrated into the signal processing path, allowing both ADC conversion and open pin detection to occur simultaneously using the same hardware components, thereby improving reliability without proportionally increasing device complexity.
Solution Approach 2:
The Sigma-Delta modulator and decimation filter are designed to serve dual purposes: they process both the normal analog input signals for ADC conversion and the bias currents for open pin detection. This multi-functionality allows the circuit to perform multiple tasks with the same hardware, resolving the contradiction between enhanced detection capability and circuit complexity.
2Measurement precision
If a separate open pin detection circuit is added, then the detection precision is improved, but the device complexity increases
Solution Approach 1:
The open pin detection circuit shares the Sigma-Delta modulator and decimation filter with the main ADC function. By merging these components, the detection precision is improved through the use of high-quality signal processing resources while avoiding the complexity increase that would result from completely separate detection hardware.
Solution Approach 2:
The ADC circuit's own signal processing components (Sigma-Delta modulator and decimation filter) are used to perform the open pin detection function. The circuit essentially detects open pins using its own existing resources, eliminating the need for additional dedicated detection hardware and thus improving detection precision without proportionally increasing complexity.
3Reliability
If real-time open pin detection is implemented, then the reliability is improved, but the loss of time for normal operation increases due to potential interruptions
Solution Approach 1:
The open pin detection operates continuously in parallel with the normal ADC conversion process. The Sigma-Delta modulator and decimation filter process both the primary analog input signals and the bias currents simultaneously without interruption. This continuous operation ensures real-time detection capability while maintaining uninterrupted normal ADC functionality, resolving the contradiction between reliability improvement and operational time loss.
Solution Approach 2:
The detection circuit continuously monitors for open pin conditions before they can cause damage. By performing preliminary detection of the bias current signals, the system can identify open pins in real-time and trigger protective actions before incorrect control signals affect the motor system, thus improving reliability without requiring operational interruptions.
Data Source
AI summary
A method includes applying a current to an input pin of an integrated circuit; converting an analog signal at the input pin to a digital stream using a Sigma-Delta modulator; converting the digital stream to a first digital output signal proportional to the analog signal in a first input range between a first analog signal value and a second analog signal value, where the first input range corresponds to a pre-determined range of the analog signal smaller than a full-scale input range of the analog signal; converting the digital stream to a second output signal; comparing the second output signal to a first threshold corresponding to a third analog signal value at the input pin that is outside of the first input range; and providing an indication of an open circuit condition at the input pin when the second output signal crosses the first threshold.