CAN Differential Signal Transmitter With Full-Bridge EMC Control
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Solution Overview
Problem
The reduction of supply voltage from 5 V to 3.3 V in CAN bus systems leads to significant electromagnetic emissions and EMC interference due to voltage level deviations, making it challenging to maintain interoperability and meet electromagnetic emission standards, especially in mixed operations with 5 V and 3.3 V subscriber stations.
Innovation Solution
A transmitting module with a full bridge configuration of four transmission stages, each with switchable resistors and polarity reversal diodes, allows for controlled switching and impedance adaptation, ensuring compliance with emission standards and enabling seamless operation of 3.3 V and 5 V nodes in a CAN bus system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the supply voltage is reduced from 5 V to 3.3 V, then the cost and power consumption are reduced, but electromagnetic emissions increase and EMC interference worsens
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the resistance values of the transmission stages based on the supply voltage level. When operating at 3.3 V, the transmission stages use different resistance values compared to 5 V operation, optimizing the signal transmission characteristics for the lower voltage while controlling electromagnetic emissions. This allows the system to maintain compatibility with both 3.3 V and 5 V subscriber stations on the same bus.
2Adaptability or versatility
If 3.3 V and 5 V subscriber stations operate simultaneously on the same bus, then interoperability and system versatility are improved, but voltage level deviations and electromagnetic interference increase
Solution Approach 1:
The transmitting module employs dynamic adjustment of transmission parameters based on the operating mode. The resistance values of the transmission stages are adaptively selected depending on whether the module is operating with 3.3 V or 5 V subscriber stations, or in mixed mode. This dynamic adaptation allows seamless interoperability between different voltage domains while minimizing voltage level deviations that cause EMC interference.
Solution Approach 2:
The patent implements parameter changes by switching between different resistance configurations in the transmission stages according to the detected operating mode. This allows the module to optimize its transmission characteristics for each voltage domain while maintaining compatibility across the mixed 3.3 V/5 V bus environment, thereby achieving interoperability without excessive electromagnetic interference.
3Device complexity
If the transmission stages use fixed resistance values, then the device complexity is reduced, but the ability to adapt to different voltage levels and bit rates is limited
Solution Approach 1:
The patent segments the transmission stages into multiple parallel current stages, each with different resistance values. This segmentation allows the system to select appropriate resistance values for different operating conditions (3.3 V vs. 5 V operation, different bit rates) without requiring a completely different transmission stage design. The segmented structure provides adaptability while keeping the overall device complexity manageable through modular implementation.
Data Source
AI summary
A transmitting module for transmitting differential signals in a serial bus system. The transmitting module has a first transmission stage for generating transmission currents for a first signal to be sent to a bus, a second transmission stage for generating transmission currents for a second signal to be sent to the bus as a signal differential to the first signal, a third transmission stage for generating transmission currents for the first signal, and a fourth transmission stage for generating transmission currents for the second signal. The first to fourth transmission stages are connected in a full bridge. The first and fourth transmission stages are connected in series. The third and second transmission stages are connected in series. The first to fourth transmission stages each have at least two current stages, each of which has a switchable resistor, wherein the switchable resistors of a transmission stage have different resistance values.