CAN Transceiver Attenuation Circuit for Common-Mode EMI
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Solution Overview
Problem
CAN transceivers in vehicle networks are vulnerable to electromagnetic interference, which causes electrical disturbances on signal lines, affecting their operational robustness.
Innovation Solution
An attenuation device is integrated or externally coupled to the transceiver, which changes resistance states based on common-mode voltage levels to attenuate common-mode disturbances, ensuring minimal impact on differential signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transceiver operates in a vehicle network environment, then it can communicate data between ECUs, but it becomes vulnerable to electromagnetic interference causing electrical disturbances on signal lines
Solution Approach 1:
The attenuation device acts as an intermediary element inserted between the transceiver terminals and the CAN bus signal lines. This intermediary component provides electrical coupling while introducing controlled attenuation characteristics that reduce the impact of common-mode disturbances from electromagnetic interference, thereby protecting the transceiver without blocking normal differential signal transmission
Solution Approach 2:
The attenuation device changes its electrical parameters (attenuation level) based on the common-mode voltage level detected on the signal lines. When common-mode voltage exceeds a threshold indicating electromagnetic interference, the device increases attenuation for common-mode signals while maintaining low attenuation for differential signals, thus adaptively responding to interference conditions
2Reliability
If an attenuation device is added to reduce common-mode disturbances, then robustness against electromagnetic interference is enhanced, but device complexity increases
Solution Approach 1:
The attenuation device is designed to perform multiple functions simultaneously: it provides controlled attenuation for common-mode signals to reduce electromagnetic interference impact, while maintaining low insertion loss for normal differential CAN bus communications. This multi-functionality is achieved through a compact structure that integrates both attenuation and signal path functions, minimizing the increase in overall device complexity
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
Enhances the robustness of the transceiver against electromagnetic interference by effectively reducing common-mode voltage disturbances while maintaining the integrity of differential signals.
Implementation Method 1
the attenuation device is configured to change from a first device state to a second device state in response to applying a common mode voltage to the device output nodes (146, 148) that is either greater than a first reference voltage VI or less than a second reference voltage V2
Implementation Method 2
the attenuation device is configured to cause a first electrical output resistance at each device output node during the first device state, and wherein the attenuation device is configured to cause a second electrical output resistance at each device output node during the second device state, wherein the second output resistance is less than the first output resistance
Data Source
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AI summary
An attenuation device for a CAN transceiver is disclosed, the attenuation device comprises two device output nodes configured to electrically couple the attenuation device via the device output nodes between two transceiver terminals of the CAN transceiver, wherein the attenuation device is configured: to change from a first device state to a second device state when a common mode voltage is applied to the device output nodes that is either greater than a first reference voltage or less than a second reference voltage, the second reference voltage being less than the first reference voltage; to cause a first electrical output resistance at each device output node during the first device state; and to cause a second electrical output resistance at each device output node during the second device state, wherein the second output resistance is less than the first output resistance. A related method and CAN transceiver are also disclosed.