CAN FD Transceiver Circuit for Faster Recessive Bus Transitions
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Solution Overview
Problem
The increasing bandwidth requirements in automotive networks are hindered by the bit rate limitation of traditional CAN systems, which is exacerbated by increased transition times from dominant to recessive levels under high bus capacitance loads, limiting the maximum baud rate and data rate in CAN FD systems.
Innovation Solution
A transceiver circuit with a frame detect and decode module that actively enables a driver module during dominant to recessive transitions, reducing transition time by actively driving the CAN bus to a recessive state, thereby improving the maximum baud rate and data rate capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If passive transition is used for dominant to recessive level change, then device complexity is reduced, but transition time increases limiting maximum baud rate
Solution Approach 1:
The transceiver circuit dynamically switches between passive transition (for recessive to dominant) and active transition (for dominant to recessive) based on the current bus state and transmission requirements. This dynamic adaptation allows the system to optimize transition speed when needed while maintaining simplicity during normal operation, thereby resolving the contradiction between device complexity and maximum baud rate.
Solution Approach 2:
The invention changes the transition mechanism parameter from always-passive to conditional-active based on the direction of level change. By modifying the transition method from static to variable, the system achieves faster dominant-to-recessive transitions without permanently increasing circuit complexity, thus improving maximum baud rate while controlling complexity growth.
2Use of energy by moving object
If passive transition is used for dominant to recessive level change, then energy consumption is reduced, but transition time increases reducing data rate
Solution Approach 1:
Instead of using active transition for all level changes (which would consume excessive energy), the invention applies active transition only partially - specifically for dominant-to-recessive transitions where speed is critical for maintaining data rate. This selective application optimizes the balance between energy consumption and productivity by using excessive action only when necessary.
3Speed
If active driver is enabled during dominant to recessive transition, then transition time is reduced improving baud rate, but device complexity increases
Solution Approach 1:
The transceiver circuit performs preliminary detection of the current bus level state before initiating a transition. By knowing the starting state in advance, the circuit can pre-configure the appropriate transition mechanism (passive or active), enabling faster dominant-to-recessive transitions without requiring complex real-time decision-making circuitry, thus improving transition time while controlling device complexity.
4Speed
If active transition is used for dominant to recessive level change, then maximum baud rate is improved, but energy consumption increases
Solution Approach 1:
The invention applies active transition only partially - specifically for dominant-to-recessive transitions where speed is critical for maintaining data rate. By using active transition only when necessary rather than continuously, the system improves maximum baud rate while avoiding excessive energy consumption that would result from always-using active transition.
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
The active transition approach significantly reduces transition times, enhancing the maximum baud rate and data rate in CAN FD systems, addressing the limitations imposed by passive transitions and high bus capacitance loads.
Implementation Method 1
actively enables the driver during dominant to recessive transitions, reducing transition time by actively driving the CAN bus to a recessive state
Data Source
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.