Full-Bridge CAN Transmitter for 3.3 V/5 V EMC Compatibility
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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 compliance with electromagnetic emission standards, especially in mixed operations with 5 V and 3.3 V nodes.
Innovation Solution
A transmitting module with a full bridge configuration of four transmission stages, each with transistors and polarity-reversal diodes, controls the switching process to adapt impedance and voltage levels, ensuring compliance with emission standards and allowing mixed operation of 3.3 V and 5 V nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the supply voltage is reduced from 5 V to 3.3 V, then cost is reduced and compatibility with modern microcontrollers is improved, but electromagnetic emissions increase and EMC compliance deteriorates
Solution Approach 1:
The patent changes the voltage parameter from 5 V to 3.3 V supply, which fundamentally alters the operating conditions of the transmitting module. This parameter change enables cost reduction and compatibility with modern 3.3 V microcontrollers while the patent compensates for the resulting EMC issues through additional circuitry and control mechanisms
2Adaptability or versatility
If 3.3 V subscriber stations are introduced into existing 5 V CAN bus systems, then cost is reduced and modern microcontroller compatibility is improved, but voltage level deviations cause signal shape mismatches and evaluation errors
Solution Approach 1:
The transmitting module acts as an intermediary between 3.3 V and 5 V systems. It includes voltage level conversion circuitry and control logic that mediates the interaction between different voltage domains, enabling 3.3 V nodes to communicate with 5 V nodes while maintaining signal integrity and preventing evaluation errors
Solution Approach 2:
The patent implements dynamic voltage level adjustment and adaptive signal shaping capabilities. The transmitting module dynamically adjusts its output signal characteristics based on the detected bus conditions and operating mode, allowing it to adapt between 3.3 V and 5 V operation modes seamlessly
3Productivity
If voltage transitions are accelerated to increase data transmission rate, then productivity is improved, but electromagnetic emissions increase and EMC compliance deteriorates
Solution Approach 1:
The patent implements periodic switching control with optimized transition timing. By controlling the switching frequency and duty cycle of the transmission stages, the system achieves high data rates while distributing the electromagnetic emissions over time, reducing peak emissions and improving EMC compliance
Solution Approach 2:
The transmitting module performs preliminary voltage level adjustment and signal conditioning before the actual data transmission. This preliminary action prepares the signal in advance, enabling faster transitions during the actual transmission without generating excessive electromagnetic emissions
Data Source
AI summary
A transmission module and a method for transmitting differential signals in a serial bus system. The transmission module has a first transmission stage for generating at least one transmission current for a first signal to be transmitted to a bus of the bus system, a second transmission stage for generating at least one transmission current for a second signal to be transmitted to the bus as a signal differential to the first signal, a third transmission stage for generating at least one transmission current for the first signal, and a fourth transmission stage for generating at least one transmission current for the second signal. The first to fourth transmission stages are connected into a full bridge, in which the first and fourth transmission stages are connected in series and the third and second transmission stages are connected in series.