Ringing Suppression Circuit for CAN Bus Transmitter Modules
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The conventional CAN bus experiences ringing phenomena due to impedance mismatches, which reduce the maximum data rate and can lead to communication failures, especially as CAN bus technology advances and baud rates increase.
Innovation Solution
A novel ringing suppression circuit is introduced, comprising a CANH driver circuit, a CANL driver circuit, and a termination component, which is applied to a transmitter module in a CAN bus. This circuit sequentially turns on transistors to control the CAN bus differential voltage, effectively suppressing ringing and improving data rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the CAN bus supports rapid data rate up to 10 Mb/s, then the data transmission speed is improved, but impedance mismatch causes signal reflections and ringing that reduce reliability
Solution Approach 1:
The circuit performs preliminary action by proactively detecting the differential voltage level before transitions occur and pre-charging/discharge the bus lines through controlled transistor switching. This preliminary voltage adjustment prevents impedance mismatch and signal reflections before they can cause ringing, thereby maintaining signal integrity at high data rates
Solution Approach 2:
The circuit dynamically changes voltage parameters by adjusting the differential voltage (Vod = VCANH - VCANL) levels based on detected bus states. By modifying voltage levels and transition timing parameters, the circuit adapts to different operating conditions and suppresses ringing while maintaining high-speed communication capability
2Ease of operation
If the bus status transitions from dominant state to recessive state, then the communication protocol operation is improved, but impedance mismatch causes signal reflections and ringing
Solution Approach 1:
The circuit employs feedback by continuously detecting the differential voltage level on the CAN bus and using this information to control the switching of transistors. The detection unit monitors bus voltage and feeds this information back to the control logic, which adjusts transistor switching timing to suppress reflections during state transitions, thereby eliminating ringing while maintaining protocol operation
Solution Approach 2:
The circuit applies preliminary anti-action by detecting upcoming state transitions and preemptively adjusting voltage levels through controlled transistor switching. Before the bus transitions from dominant to recessive state, the circuit pre-charges the lines to reduce voltage spikes and reflections, thereby preventing ringing before it occurs
Data Source
AI summary
A ringing suppression circuit applicable to a transmitter module in a controller area network is provided, which includes a CANH driver circuit, a CANL driver circuit, a first operable circuit transmitting a CAN high signal, a second operable circuit transmitting a CAN low signal, and a termination component connected between the first operable circuit and the second operable circuit. By sequentially turning on a first, second, and third transistor of the CANH driver circuit and sequentially turning on a fourth, fifth, and sixth transistor of the CANL driver circuit, conventional ringing phenomenon is effectively suppressed. A plurality of transistors may also be configured for implementing the CANH driver circuit or the CANL driver circuit for further reducing a glitch. The transmitter module employing the proposed ringing suppression circuit is able to pull the bus to a recessive state and meanwhile suppress the ringing and improve the maximum data rate.