CAN Bus Driver Mode Switching for Higher Bandwidth
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Solution Overview
Problem
The challenge of achieving increased data bandwidth in CAN-bus protocols while maintaining backwards compatibility and addressing issues with non-ideal network topologies, which limit maximum bus speeds and data transmission efficiency.
Innovation Solution
The implementation of an enhanced driver mode for a shared bus using active driver circuits to actively drive both dominant and recessive signal levels, along with a control circuit to enable or disable these drivers based on transmission modes, and a dedicated CANFD transceiver that changes operation during the data field to improve EMC and data bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If passive bias is used to set the signal bus to recessive value, then backwards compatibility with older CAN protocol is maintained, but data bandwidth and bus speed are limited
Solution Approach 1:
The system dynamically switches between two operational modes: a first mode using passive bias for backwards compatibility with older CAN protocols, and a second mode using active driving for both dominant and recessive values to achieve higher data bandwidth. The control circuit enables this dynamic transition based on protocol requirements, allowing the same physical layer to serve both legacy and enhanced applications.
2Productivity
If active driver circuit is added to drive the bus to recessive value, then data bandwidth is increased, but device complexity increases
Solution Approach 1:
The patent merges the functions of dominant and recessive driving into a single bidirectional active driver circuit. This integrated approach allows the circuit to actively drive the bus to either dominant or recessive values as needed, eliminating the need for separate driving mechanisms and reducing overall system complexity while achieving enhanced data bandwidth.
3Speed
If bidirectional active driving is implemented, then bus speed and data transmission efficiency are improved, but EMI and ringing issues occur
Solution Approach 1:
The patent converts the potentially harmful effects of bidirectional active driving (EMI and ringing) into beneficial outcomes by carefully controlling the driving时序 and voltage levels. The control circuit is designed to minimize simultaneous bidirectional driving, and the active driver circuits are configured to reduce signal reflections and EMI generation, thereby achieving high bus speeds while mitigating the harmful effects.
Data Source
AI summary
A device includes a transmission circuit that is configured and arranged to transmit data in accordance with a signal bus protocol that uses passive bias to set a signal bus to a recessive value in the absence of an actively-driven signal value. The transmission circuit includes a first driver circuit that is configured and arranged to actively drive the signal bus to a dominant value that is different from the recessive value. The transmission circuit also includes a second driver circuit that is configured and arranged to actively drive the signal bus to the recessive value. A control circuit is configured and arranged to disable the second driver circuit in response to the device operating in a first data transmission mode, and to enable the second driver circuit in response to the device entering a second transmission mode.