Bounded Current Sense Circuit for EMI-Robust Output Control
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Solution Overview
Problem
Current sensing circuits are vulnerable to electro-magnetic interference (EMI) disturbances, which can cause abnormal operation and lead to failures in safety-critical situations, necessitating a more robust tolerance to such disturbances.
Innovation Solution
A current sense circuit is designed to bound sensed currents within predetermined minimum and maximum limits, utilizing current mirrors for process, voltage, and temperature independence, and incorporating a current limiter and clamp circuit to maintain a known output current during EMI conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current sensing circuits are used, then the circuit can perform current sensing function, but the circuit is vulnerable to EMI disturbances causing abnormal operation
Solution Approach 1:
The current sense circuit performs preliminary bounding of the sensed current through current limiting circuitry before the current is processed by subsequent stages. This preliminary action ensures that even if EMI disturbances occur, the current remains within safe bounds, preventing abnormal operation and protecting downstream circuitry from damage.
Solution Approach 2:
The circuit incorporates current bounding and limiting mechanisms that act as a protective cushion against EMI disturbances. By pre-establishing current bounds and using clamp circuits, the system creates a buffer zone that absorbs the impact of EMI before it can affect the normal operation of the current sensing circuit or downstream components.
2Reliability
If current bounding circuitry is added to improve EMI robustness, then reliability improves, but device complexity increases
Solution Approach 1:
The current bounding functionality is merged with the existing current sensing circuit architecture. The current limit circuitry is integrated into the signal path, combining the sensing function with the protective bounding function in a unified circuit design, thereby reducing overall complexity compared to adding separate protective stages.
Solution Approach 2:
The current sense circuit is designed to perform multiple functions: accurate current sensing, current bounding, and EMI protection. By making the circuit multi-functional, the need for separate dedicated protective circuits is reduced, thereby managing complexity while achieving robustness against EMI disturbances.
Data Source
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AI summary
A current sense circuit is provided. The current sense circuit includes an input terminal coupled to sense an input current. A first terminal of a diode is coupled as the input terminal. A current limiter has a first terminal coupled to a second terminal of the diode. A current source is coupled to a second terminal of the current limiter and configured to generate a first current. A current mirror includes a first leg coupled to the current limiter and the current source and a second leg coupled for providing an output current.