Department: PD
Group: VE
By: Pooria Akbari Haghighi
Title: How to Decide Which ECUs go on a Low-Speed CAN (CAN-LS) versus a high-speed CAN (CAN-HS)
Deciding which ECUs (Electronic Control Units) go on a Low-Speed CAN (LS-CAN) versus a High-Speed
CAN (CAN-HS) network depends on a mix of functional, performance, cost, and safety requirements.
Here’s a structured approach to help you decide:
1. Understand the Functional Role of Each ECU
HS-CAN (500 kbps – 1Mbps):
Used for critical and real-time systems
Typical ECUs: Engine Control Unit, Transmission, ABS, ESP, Airbags, etc.
Reason: These systems need fast and reliable communication.
LS-CAN (typically 125 kbps or lower):
Used for non-critical, body-related functions.
Typical ECUs: Door modules, Seat control, HVAC, Lighting, Window Lifter, etc.
Reason: These do not require high-speed or real-time data exchange.
2. Consider Safety and Timing Requirements
If an ECU need to react quickly or impacts vehicle safety, it goes on HS-CAN.
If the ECU controls comfort features where delays are acceptable, it can go on LS-CAN.
3. Evaluate Bus Load and Bandwidth Needs
High-bandwidth ECUs (e.g., those streaming frequent sensor data) should be placed on HS-CAN.
LS-CAN is suitable for infrequent or low-priority messages.
4. Check for Legacy or Supplier Constraints
Some modules may be pre-configured by the supplier for a certain CAN speed.
OEMs may standardize certain ECUs to a particular bus type to reduce complexity.
5. Cost Considerations
LS-CAN is cheaper due to simpler transceivers and reduced EMI requirements.
It’s preferred for peripheral ECUs where high performance is not needed.
6. Network Architecture and Topology
Use gateway ECUs to bridge between LS-CAN and HS-CAN.
Minimize the number of gateway by clustering ECUs with similar requirements.