CAN FD Transceiver Active Recessive Transition
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Solution Overview
Problem
The transition time from dominant to recessive levels in CAN FD systems is increased due to high bus capacitance, limiting the maximum baud rate and data rate, especially under high bit-rate conditions.
Innovation Solution
A transceiver circuit with a frame detect and decode module that actively enables the driver during dominant to recessive transitions, reducing transition time by actively driving the CAN bus to a recessive state, rather than relying on passive transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive transition from dominant to recessive state is used, then device complexity is reduced, but transition time increases limiting maximum baud rate
Solution Approach 1:
The patent applies dynamics by making the transceiver circuit's transition mechanism adaptive. The system dynamically selects between passive transition (for standard CAN) and active transition (for CAN FD high-speed mode) based on the communication mode requirements. This dynamic behavior allows the circuit to optimize transition speed when needed while maintaining simplicity for standard operations, thereby resolving the contradiction between device complexity and transition speed.
Solution Approach 2:
The patent changes the electrical parameters of the transceiver circuit by enabling active driving capability during dominant-to-recessive transitions in CAN FD mode. This parameter change allows the output driver to actively pull the bus voltage to the recessive state, significantly reducing transition time compared to passive RC-based transitions. The parameter change is controlled by the mode selection logic that detects CAN FD framing, enabling the system to achieve higher baud rates when required.
2Loss of time
If active driving during dominant to recessive transition is implemented, then transition time is reduced, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing the transceiver circuit to handle both standard CAN and CAN FD protocols with a single unified structure. The output driver stage is designed to provide both passive transition capability (for standard CAN) and active transition capability (for CAN FD). The frame detect and decode module controls which function is activated based on the protocol mode, allowing the same hardware to serve multiple purposes and reducing the need for separate dedicated circuits for each mode.
Solution Approach 2:
The patent extracts the active driving function from the standard CAN transceiver operation and applies it selectively only when needed for CAN FD high-speed mode. The frame detect and decode module identifies CAN FD frames and triggers the active transition mechanism only during those specific communication sessions. This extraction approach allows the system to gain the performance benefits of active driving without permanently increasing the baseline device complexity, as the enhanced functionality is activated only when required.
3Ease of operation
If passive transition is used for dominant to recessive state, then ease of operation is maintained, but data rate capability is limited
Solution Approach 1:
The patent applies dynamics by making the transceiver circuit's transition mechanism adaptive. The system dynamically selects between passive transition (for standard CAN) and active transition (for CAN FD high-speed mode) based on the communication mode requirements. This dynamic behavior allows the circuit to optimize transition speed when needed while maintaining simplicity for standard operations, thereby resolving the contradiction between device complexity and transition speed.
Solution Approach 2:
The patent changes the electrical parameters of the transceiver circuit by enabling active driving capability during dominant-to-recessive transitions in CAN FD mode. This parameter change allows the output driver to actively pull the bus voltage to the recessive state, significantly reducing transition time compared to passive RC-based transitions. The parameter change is controlled by the mode selection logic that detects CAN FD framing, enabling the system to achieve higher baud rates when required.
Data Source
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AI summary
A transceiver circuit for operating in a controller area network (CAN), having a CAN bus network and a control unit, that supports a flexible data rate (CAN FD), is described. The transceiver circuit comprises: a transmit CAN path and a receive CAN path; an input node on the transmit CAN path; a detection module operably coupled to the input node on the transmit CAN path and arranged to receive an input frame from the control unit before the input frame is transmitted on the CAN bus network and determine whether the input frame on the transmit CAN path comprises a CAN FD frame; and at least one switching module, operably coupled to the detection module and coupleable to the CAN bus network, where the at least one switching module is operable to impart a first voltage value on the CAN bus network in response to the input frame being determined as comprising a CAN FD frame.