Floating Input Detection via Common-Mode Amplifier Thresholding
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Solution Overview
Problem
Existing methods for detecting floating input terminals in electronic devices are either invasive, affecting terminal impedance, or slow, and often require high voltage components or dedicated detection cycles, which can disrupt normal circuit operation.
Innovation Solution
A data acquisition system with a signal input terminal, an analog-to-digital converter, and an analog front end circuit that includes a programmable gain amplifier and a common mode amplifier, which detects floating input terminals by varying a common mode input voltage and comparing the output signal to threshold voltages using coarse and fine detection circuits without affecting terminal impedance or requiring high voltage components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing detection methods are used to detect floating input terminals, then detection capability is achieved, but terminal impedance is affected and circuit operation is disrupted
Solution Approach 1:
The patent introduces a common mode amplifier as an intermediary component that couples to both the inverting and non-inverting inputs of the programmable gain amplifier. This intermediary structure allows detection of floating inputs through common mode voltage measurements without directly interfering with the differential signal path, thereby maintaining terminal impedance and allowing continuous circuit operation.
Solution Approach 2:
The detection function is segmented from the main signal processing path. The common mode amplifier separately monitors the common mode voltage at the inputs, while the programmable gain amplifier continues its normal differential amplification function. This segmentation allows independent operation of detection and signal processing, preventing mutual interference.
2Measurement precision
If high voltage components are used for detection, then detection sensitivity is improved, but device complexity and safety requirements increase
Solution Approach 1:
The patent changes the detection parameter from high voltage measurements to common mode voltage measurements. By monitoring the common mode voltage level and its changes in response to test signals, the system achieves sensitive detection of floating inputs using standard voltage levels, eliminating the need for high voltage components while maintaining detection effectiveness.
Solution Approach 2:
The patent replaces potential high voltage mechanical or electronic switching mechanisms with an electronic common mode voltage measurement approach. The common mode amplifier electronically senses the input state through voltage level detection, substituting complex high voltage test mechanisms with a simpler electronic sensing system.
Data Source
AI summary
A floating input detection method and circuits. A method for detecting a floating signal input terminal includes providing a common-mode input voltage to a first amplifier coupled to the signal input terminal, and providing an output signal generated by the first amplifier to: a non-inverting input of a second amplifier coupled to the signal input terminal, an inverting input of the second amplifier, coarse detection circuitry, and fine float detection circuitry. The method also includes comparing, by the coarse detection circuitry, the output signal to a first threshold voltage, and determining the signal input terminal to be not floating responsive to the comparing indicating that the output signal is greater than the first threshold voltage.