How much do you know about CAN SIC? Have you used the new generation of in-vehicle network protocol?

Recently, Naxin Micro announced the launch of the automotive-grade CAN SIC (Signal Improvement Capability) NCA1462-Q1 based on its self-developed innovative ringing suppression patent. NCA1462-Q1 is further compatible with the CiA 601-4 standard while meeting the ISO 11898-2:2016 standard, and can achieve a transmission rate of 8Mbps, which is significantly better than the current mainstream CAN FD in-vehicle communication solution.

Although everyone is familiar with CAN or CAN FD, they know relatively little about CAN SIC. The relevant interface products have only been mass-produced in the past two years. This time, taking advantage of the release of new products by Nanochip, we contacted Chen Zhangjie, the technical marketing manager of Nanochip, and discussed the relevant topics around CAN SIC.

Why develop CAN SIC?

With the rise of the concepts of autonomous driving and regional control, ECUs are being extensively integrated with each other, which means higher integration, more nodes, more complex star topology, and higher transmission rates.

This brings a huge challenge to the CAN FD bus - that is, in a more complex star topology network, due to the high transmission rate and complex topology changes, severe ringing will occur, resulting in an increase in the bit error rate and affecting signal transmission.

The current CAN FD standard claims to be defined up to 5Mbps, but in actual applications it is difficult to reach more than 2Mbps. Although customers want to increase the speed, for the sake of signal integrity, they often have to sacrifice the rate and reduce the size of the node to reduce the impact of ringing.

CAN SIC can easily resolve this contradiction.

How does CAN SIC reduce ringing?

To understand the principle of CAN SIC, we must first look at the cause of ringing.

Ringing refers to an oscillation phenomenon caused by multiple reflections of the signal on the transmission line due to signal reflection caused by impedance mismatch and other reasons during the communication process of the CAN bus. A higher communication rate means a narrower bit width time. The current CAN FD 2Mbps is shorter than the previous HS CAN 500kbps bit width time from 2000ns to 500ns. The same intensity of ringing interference, at a higher communication rate, is more likely to cause communication errors because it does not have enough time to decay below the implicit differential voltage judgment threshold.

To solve this problem, in 2019, the CAN FD SIC (Signal Improvement Capability) signal enhancement standard CiA (CAN in Automation) 601-4 was released to suppress ringing to match the requirements of modern domain control and high-speed communication systems.

Compared with CAN FD, the biggest optimization of CAN SIC is the addition of a strong drive circuit. As mentioned above, ringing often occurs from dominant to invisible state, so an additional strong drive circuit can be added during the conversion process to control the switching slope of the bus level to ensure that the data is not wrong.

CAN SIC may become the mainstream standard

"No matter which standard is formulated, it is to meet the needs of the time. Each generation has its own mission and will continue to improve during the evolution process," said Chen Zhangjie.

The CAN bus has gone through multiple standards. It was first invented by Bosch in Germany in the 1980s. The first mass-produced model using the CAN bus communication protocol was the Mercedes-Benz S-Class sedan in 1991. To this day, the CAN bus is still the main communication bus in the car. With the acceleration of automotive electronics intelligence, the CAN bus has also begun to be further upgraded. In 2003, the CAN bus was upgraded to HS CAN, but it was still based on the first-generation technology. In 2011, the second-generation CAN bus CAN FD began to be developed. In 2015, the CAN FD standard, ISO11898, was released. In 2019, the CAN FD SIC (Signal Improvement Capability) signal enhancement version standard CiA (CAN in Automation) 601-4 was released. In 2021, the lightweight version of CAN FD, CAN FD Light standard CiA 604-1, was released. In December 2021, the third-generation CAN bus, the CAN XL standard CiA 610-1, was released. At present, the CAN XL standard has not been fully completed. These new standards will eventually be converted to ISO11898-2.

Chen Zhangjie said: "At that time, the demand for the CAN bus was to speed up, and there were not many complex topology requirements, so there was no ringing problem. However, as the demand for complex topology and high speed increased, CAN FD could not meet it, so CiA 601-4 was born."

In addition, for the next generation of CAN XL, the ringing problem still needs to be solved, and CAN SIC can also lay the groundwork for speed increase and multi-node complex communications in advance.

In addition to solving the current problems of CAN FD, CAN SIC has another major mission, which is to cope with the competition from Ethernet. Nowadays, the vehicle backbone network has been Ethernet-based, but the control end has not yet been implemented. Considering its cost and the adaptation of manufacturers in software or other aspects, CAN is still one of the dominant players in the future.

Chen Zhangjie emphasized that the evolution of CAN SIC is faster than expected. "As the concepts of domain control and regional architecture are widely accepted by OEMs, the recognition of CAN SIC continues to increase, and even some relatively conservative OEMs are gradually accepting this technology. I believe that CAN SIC will have great potential in the future."

How Nanochip developed CAN SIC

The measured transmission rate of Nanochip's CAN SIC can reach 10Mbps, which fully meets the CiA 8Mbps specification requirements.

Chen Zhangjie said that the biggest challenge in CAN SIC development is actually the compatibility between the drive architecture and the EMI architecture. It is not difficult to simply make a good drive circuit, but it will sacrifice performance in other aspects, especially the handling of non-linear relationships such as EMI.

"Chip design itself is a matter of trade-offs." Chen Zhangjie added that in addition to paying attention to EMI, cost is also a major consideration. The performance of Nanochip's products is not inferior to that of foreign manufacturers, and at the same time it must be more cost-effective, so it is necessary to continuously optimize the design to achieve higher performance with a smaller area (lower cost). "In addition, the product itself is one aspect, and more importantly, the product should be developed from a system perspective." This includes constraints such as EMI, ESD, and cost optimization, etc.

Chen Zhangjie also emphasized that Naxinwei has been deeply engaged in the development of IP. In the process of CAN SIC development, many invention patents were born, and they were IP-based and shared with other product portfolios, opening up the platform for underlying research and development. "For chips, one of the core competitiveness is IP. Naxinwei is also continuously developing and optimizing these core IPs to form a complete roadmap." Chen Zhangjie added.

Detailed explanation of Naxinwei's new CAN SIC product

According to official information from Nachip, Nachip's NCA1462-Q1 has optimized EMI design based on an innovative patented architecture and is tested in accordance with the IEC62228-3 standard, fully meeting the requirements.

NCA1462-Q1 achieves ESD performance of more than ±8kV by optimizing the circuit structure and layout area. It can not only calmly deal with the sudden electrostatic discharge threat during the driving of the car, provide more reliable circuit protection, but also achieve better device cost. With its ultra-high EMC/ESD performance, NCA1462-Q1 can also help engineers save common-mode inductors or TVS tubes in peripheral circuits in some designs. In addition, the more flexible VIO design as low as 1.8V can further save the use of LDO or level conversion in the system, helping engineers reduce overall costs.

The bus fault protection voltage is ±58V, which can be achieved for both CAN Low and CAN High, truly achieving high voltage resistance, thus helping customers reduce the risk of breakdown.

In addition, it is worth mentioning that in CAN SIC, EMI can be subdivided into explicit EMI and implicit EMI. For example, some products have good explicit EMI, while some products have good implicit EMI. Naxinwei has achieved comprehensive optimization of explicit and implicit EMI by taking advantage of each other's strengths and making up for each other's weaknesses.

Chips must be market leaders

The market prospects of CAN SIC are very certain, but as of now, not all CAN interface manufacturers have launched CAN SIC products, especially domestic chip suppliers, which are very few.

"As of the current point in time, although the demand for CAN SIC is very clear, it is impossible for the product to suddenly become ubiquitous. It requires a gradual process," said Chen Zhangjie.

Chen Zhangjie also emphasized that Naxinwei has never been a follower. Whether it is CAN transceiver or CAN SIC, it has always made advance arrangements based on market demand and predictions, and defined complete products and roadmaps. For this reason, Naxinwei became the earliest manufacturer to mass-produce CAN SIC.

"Innovation cannot follow the crowd. We cannot wait until others have done it and then do it after we see that there is real market demand. For the chip market, this is already too late," said Chen Zhangjie.

Although there are not many CAN SIC suppliers, there are many CAN suppliers. Why does Nanochip want to enter this market? Chen Zhangjie said that as the main bus technology for automobiles, its market capacity is very large. Each car needs dozens of them, and the market is always in high demand. Moreover, Chen Zhangjie said: "The CAN interface seems simple, but there is a certain threshold to do it well. As a general material, it can best test the company's capabilities, which include cost control, market coverage, R&D strength, supply chain, etc."