Signal Improvement Drives Next-Generation Automotive CAN Performance

­ECUs typically manage a whole host of vital vehicle functions such as powertrain control, lighting, safety, and infotainment. The number of ECUs varies per vehicle, but if we look at a luxury model, it is hardly unusual to see to see 150, or even more. And even in lower-end vehicles, the total number will be approaching the 100 mark. And according to a recent (September 2024) analyst report from Fortune Business Insight, “most vehicles contain more than 125”. A major reason for the rising number of ECUs in vehicles can be attributed to just three recent automotive trends.

Electrification, which reduces the environmental impact – particularly the local impact – has been a key driver. So too has the safety-led move to ADAS (advanced driver-assist systems) and autonomous driving capabilities; with research from the US drivers’ organization AAA suggesting the addition of just six ADAS systems could cut the number of deaths on US roads by 29% (or more than 12,000 per year) with the subsequent shift to full autonomy taking these life-saving advances further.

And finally, also of note in driving the rise in ECU count is the increasing adoption of vehicle connectivity. This includes not just cellular, navigation and short-range data communication, but also V2X and will soon even include vehicle-to-satellite communication. Collectively, these have enabled the integration of safer infotainment and navigations systems and is improving the overall user experience.

However, the proliferation of ECUs has led to the addition of hundreds of millions of lines of code and this requires the urgent development of more robust communication networks within vehicles to ensure data can be seamlessly exchanged between many different systems.

The need to support higher data rates

Along with Ethernet, the Controller Area Network (CAN) bus has long been the backbone of automotive communication systems for many years. The reason for this is that it provides a reliable and cost-effective solution for intra-vehicle data exchange. It is well trusted by virtually all automotive OEMs to manage in-vehicle communications (from sensors to actuators) and is ubiquitous.

However, as the complexity and data demands of automotive systems have grown, the traditional CAN protocol has become outmoded. The introduction of CAN Flexible Data-Rate (CAN FD) in 2012 was a significant step forward, designed to support higher data rates and larger data payloads compared to classic CAN.

But even with this, the increasing volume of data generated by modern ECUs continues to push the limits of CAN FD and one of the primary challenges lies in maintaining reliable signal communication, particularly in scenarios involving multi-node, long-distance, and high-speed data transmission.

Click image to enlarge

Table 1: a comparison of key differences between CAN and CAN-FD

During high-speed data transmission, signal communication failures become more prevalent. Multi-node networks and extended cable lengths introduce increased signal reflections and electromagnetic interference (EMI), which can lead to data corruption and communication errors. These issues are exacerbated in star network topologies where multiple nodes are connected to a central point, increasing the likelihood of signal reflections. As a result, the effective data rate of CAN FD is often throttled from its theoretical 5 Mbps rate to under 2 Mbps, limiting its ability to meet the demands of next-generation automotive applications.

The challenges of ringing

Ringing is one of the most common and problematic issues in high-speed CAN FD networks, leading to communication errors and data loss. It occurs when a signal transition induces oscillations that persist and interfere with subsequent signals, making it difficult to reliably determine the bus signal's true level until the ringing dissipates. Ringing is typically caused by impedance mismatches, improper termination, and reflections within the network, which are more pronounced in complex multi-node and long-distance setups.

These oscillations can severely degrade signal quality, particularly in environments with high EMI. As data rates increase, the tolerance for such disturbances diminishes, making it critical to address ringing to ensure reliable communication. Traditional methods of mitigating ringing, such as improved network termination and shielding, often cannot fully eliminate the issue, particularly in densely-packed automotive environments.

Addressing ringing challenges

To effectively address the challenges posed by ringing, innovative solutions are required. Patented ringing suppression technology offers a robust approach to mitigating signal oscillations and improving overall signal integrity in high-speed CAN FD networks. This technology works by dynamically adjusting the signal characteristics to dampen oscillations and prevent ringing from affecting subsequent data transmissions.

One effective implementation of this technology involves incorporating specialised circuitry within CAN transceivers to actively monitor and counteract signal reflections. By doing so, these transceivers can maintain high signal quality even in complex network topologies with multiple nodes and long cable runs. Additionally, advanced filtering techniques can be employed to minimise the impact of EMI, further enhancing the reliability of CAN FD communications.

These ringing suppression techniques can also be combined with other signal improvement capabilities to provide a much more comprehensive solution. For instance, optimising the physical layer design and using differential signalling can help mitigate common-mode noise and improve electromagnetic compatibility (EMC). By integrating these advanced technologies, automotive communication systems can achieve higher data rates and more reliable performance for the next generation of in-vehicle networks.

In response to the growing need for enhanced CAN FD performance, NOVOSENSE Microelectronics has developed the NCA1462-Q1, an automotive-grade CAN transceiver featuring Signal Improvement Capability (SIC) based on its proprietary innovative ringing suppression patent. The NCA1462-Q1 is designed to meet the stringent requirements of modern automotive applications, providing a robust and reliable solution for high-speed in-vehicle communications.

Click image to enlarge

Figures 2a, 2b, 2c: NCA1462-Q1's proprietary ringing suppression reduces signal reflections and ringing in complex, multi-node topologies

The NCA1462-Q1 is fully compatible with the CiA 601-4 standard while adhering to the ISO 11898-2 standard, ensuring seamless integration with existing automotive networks. It is capable of achieving data rates of up to 8 Mbps, significantly higher than traditional CAN FD solutions. This enhanced data rate is made possible by NOVOSENSE's patented ringing suppression technology, which maintains excellent signal quality even in challenging network configurations such as star topologies with multiple nodes.

Click image to enlarge

Figure 3: NCA1462-Q1 EMI test chart (without common mode choke).

In addition to its advanced signal improvement capabilities, the NCA1462-Q1 offers ultra-high EMC performance and a flexible input offset voltage (VIO) design as low as 1.8 V, simplifying system design and reducing overall costs. The transceiver's compatibility with mainstream classic CAN and CAN FD transceivers ensures easy integration into existing systems. It also meets AEC-Q100, Grade 1 requirements and supports a wide operating temperature range of –40°C to 125°C, making it suitable for a variety of automotive environments.

The NCA1462-Q1 includes additional features for enhanced reliability and functionality such as over-temperature protection, TXD explicit timeout protection, and remote wake-up in standby mode.

Available in SOP8 and DFN8 packages, the NCA1462-Q1 with its innovative signal improvement capabilities offers a versatile solution for automotive manufacturers seeking to address the challenges of high-speed data transmission and signal integrity and meet the rapidly evolving demands of next-gen automotive networks.
 

NOVOSENSE Microelectronics