Ringing Suppression Circuit for CAN Bus Impedance Mismatch
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Solution Overview
Problem
In vehicle CAN networks, the addition of nodes can lead to impedance mismatches, resulting in ringing issues during signal transmission, which affect communication quality and accuracy.
Innovation Solution
A ringing suppression circuit is introduced, comprising a terminator and a switching element controlled by a signal generation circuit that connects the terminator between bus lines for a predetermined period upon detecting a transition from dominant to recessive, thereby suppressing ringing and ensuring stable communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a termination resistor is disposed at the end of the CAN bus, then communication quality is improved, but ringing occurs during signal transmission due to impedance mismatch when CAN nodes are added
Solution Approach 1:
The patent applies the dynamics principle by making the termination resistor switchable between connected and disconnected states based on detected signal transitions. The switching element dynamically adjusts the termination resistor's connection state in response to dominant-to-recessive transitions, allowing the system to adapt to changing impedance conditions and suppress ringing while maintaining communication quality.
Solution Approach 2:
The patent implements feedback by using the reception circuit to detect signal transitions and feed this information back to the control signal generation circuit, which then controls the switching element. This closed-loop feedback mechanism ensures that the termination resistor is activated only when needed to suppress ringing, preventing false dominant detections while maintaining stable communication.
2Object-affected harmful factors
If the termination resistor is continuously connected to suppress ringing, then ringing is reduced, but false dominant detections occur during signal transitions
Solution Approach 1:
The patent applies periodic action by activating the termination resistor only during specific periods following dominant-to-recessive transitions, rather than continuously. The switching element connects the termination resistor for a predetermined time after detecting the transition, providing ringing suppression exactly when needed without interfering with ongoing signal transmissions or causing false detections.
Solution Approach 2:
The patent implements preliminary action by activating the termination resistor in advance after detecting a dominant-to-recessive transition, before the next signal transition occurs. This preliminary connection of the termination resistor prevents ringing from affecting subsequent signal detection, ensuring accurate period determination while maintaining communication stability.
Data Source
AI summary
A ringing suppression circuit according to an embodiment includes a terminator, a switching element configured to connect the terminator between first and second bus lines, and a control signal generation circuit configured to accept a reception result of a signal from a reception circuit that receives the signal transmitted through the first and second bus lines, and generate a control signal for controlling the switching element on a basis of the reception result.