Galvanically Isolated CAN Link for High-Speed Microcontroller Communication
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Solution Overview
Problem
Existing Single Wire CAN transceivers are limited by low data transmission speeds and lack of galvanic isolation, which restricts their use in applications requiring high-speed data transfer and safety redundancy, especially in automotive systems like steering angle sensors.
Innovation Solution
A system comprising diodes and pull-up resistors with galvanic isolation, coupled with an AND logic gate, enhances data communication between microcontrollers, achieving up to 8 Mbps data rates and ensuring electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Single Wire CAN transceiver is used to reduce hardware complexity and cost, then device complexity is reduced, but data transmission speed deteriorates to 33-100 Kbps
Solution Approach 1:
The system segments the communication interface into two independent microcontrollers (A and B), each with its own CAN controller and transceiver. This segmentation allows each side to operate at optimal speeds while maintaining galvanic isolation, resolving the contradiction between simplified hardware and high-speed communication.
Solution Approach 2:
The patent introduces an intermediary galvanic isolation barrier between the two CAN bus systems. This mediator enables high-speed data transmission by allowing differential signaling on each side while blocking galvanic currents, thus achieving both hardware simplicity and high speed through 8 Mbps CAN-FD protocol.
2Ease of manufacture
If Single Wire CAN transceiver is used to simplify hardware, then ease of manufacture is improved, but galvanic isolation capability deteriorates (lacks isolation)
Solution Approach 1:
The galvanic isolation barrier serves as an intermediary component that maintains electrical isolation between subsystems while enabling communication. This resolves the contradiction by providing both ease of manufacture (through standardized isolation components) and reliable galvanic isolation for safety-critical applications.
Solution Approach 2:
The patent extracts the galvanic isolation requirement from the transceiver itself and implements it as a separate isolation barrier component. This extraction allows the use of simple CAN transceivers on each side while maintaining isolation through the dedicated barrier, improving ease of manufacture while ensuring reliability.
3Productivity
If CAN-FD protocol is used to achieve 8 Mbps data rate, then productivity is improved, but device complexity worsens compared to Single Wire CAN
Solution Approach 1:
The system segments the high-speed communication path into two isolated CAN-FD interfaces, allowing each microcontroller to implement the full 8 Mbps protocol capability independently. This segmentation enables high productivity on each side while managing complexity through modular, standardized interfaces.
4Reliability
If redundancy is added to ensure fail-operational behavior, then reliability is improved, but device complexity worsens
Solution Approach 1:
The galvanic isolation barrier acts as a protective intermediary that enhances reliability by preventing fault propagation between subsystems. This physical isolation provides inherent fail-operational capability without requiring complex redundant hardware, as the barrier itself prevents single-point failures from affecting the entire system.
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 solution significantly improves data transfer rates by up to 240 times, meeting the requirements for high-speed, fail-operational systems with galvanic isolation, suitable for automotive applications.
Implementation Method 1
a set of diodes, diode A and a diode B, installed in series in a Tx output line of a CAN controller comprised in each of the two microcontrollers
Implementation Method 2
an isolation barrier, installed in series in a Rx input line B of a CAN controller B of the microcontroller B and in series with an anode output of diode B connected to the Tx output line B of the CAN controller B, adapted to provide an isolated Rx input line B and an isolated Tx output line B
Implementation Method 3
a pull-up resistor A connected with a first terminal to a voltage regulator A and a second terminal connected simultaneously to the isolated Rx input line B, to the isolated Tx output line B
Data Source
AI summary
A system to improve CAN communications between microcontrollers, where the CAN Transceiver is completely discarded and replaced with a galvanic isolated solution. With the proposed solution, it is possible to obtain CAN data transfer rates of 8 Mbps (however theoretically can go as high as baud rates of 12 Mbps depending on the type of galvanic isolation) while ensuring galvanic isolation between microcontrollers. It balances reducing the necessary hardware while maintaining or outperforming all the functionalities that a CAN transceiver with full galvanic isolation implemented would provide. The discrete hardware has a wide range of operability in different scenarios from wide voltage ranges or no common ground while being ideal for high speed transfers between microcontrollers while maintaining all the advantages that a CAN communication provides, either be built in error detection or robustness with bit monitoring, bit stuffing, frame check, acknowledgement check and cyclic redundancy check.