From the development history of CAN, let’s talk about how to choose an in-vehicle network solution

1. HS-CAN

In the 1980s, with the electrification of automobiles, the number of ECUs (Electric Control Units) in the car increased, making the network topology for communication between modules more and more complex, and the weight and cost of the wiring harness becoming higher and higher. . Under this demand, the CAN bus was developed to replace expensive and bulky communication harnesses. It uses two twisted pairs to transmit signals and can transmit signals at a rate of 1Mbps over a distance of 40 meters. In 1991, the CAN bus technical specification (Version 2.0) was formulated and released. In 1993, the ISO organization officially announced the CAN international standard ISO11898. In addition to the CAN protocol, it also standardized the physical layer definition.

2. CANFD

As the HS-CAN bus load rate becomes higher and higher in practical applications, some car manufacturers even have a bus load rate as high as 95%, and higher-speed CANFD has emerged. CANFD inherits most of the features of CAN, such as the same physical layer, arbitration mechanism, etc. And CANFD is backward compatible with HS-CAN. Compared with the traditional HS-CAN bus, CANFD has two upgrades:

• Support variable communication rate – maximum 5Mbps ~ 8Mbps

• Supports longer data length – up to 64 bytes of data

In 2015, the ISO organization has officially recognized CANFD and adopted the updated ISO11898-1 standard.

3. CANXL

Looking to the future, discussions are also underway about what the next generation of CAN will look like. At the 17th International CAN Conference in 2020, the CiA Association (CAN in Automation) introduced the third-generation CAN communication technology CAN XL (CAN Extra Long). The data field length is increased to a maximum of 2048 byte, and the rate is further increased to 10Mbps or even 20Mbps. The definition of the CANXL physical layer is still in progress. Infineon has developed corresponding IP and internal test chips to prepare for the future launch of CANXL transceivers that meet market needs.

Signal ringing is common in CAN communication, especially in star topology when the bus level switches from dominant state to recessive state.

Higher communication rate means a narrower bit width time. The current CANFD's 2Mbps bit width time is shortened from 2000ns to 500ns compared with the previous HS-CAN's 500kbps. Ringing interference of the same intensity, at a higher communication rate, does not have enough time to decay below the recessive differential voltage determination threshold, which makes it easier to cause communication errors. The figure shows a comparison of the waveforms when the same node in the same network topology sends 500kbps and 2Mbps CAN signals respectively.

In order to reduce the ringing effect, the current mainstream approach is to reduce the size of the CAN network, reduce the number of nodes, shorten the length of branch lines, and try to use linear topology. These measures can indeed effectively reduce ringing intensity, but they also bring some disadvantages:

• The number of CAN buses is increased, for example, a 10-node bus is split into two 5-node buses;

• Increased the need for gateways to cope with more information interactions between different buses;

• Measures such as shortening the branch line length and changing the topology structure conflict with the vehicle module layout.

In order to cope with the above difficulties and challenges, Infineon launched CANSIC (CAN Signal Improvement Capability) signal improvement transceivers—TLE9371SJ & TLE9371VSJ. The transceiver can effectively control the ringing intensity from the transmitting end, reduce the signal ringing effect, and improve the bus signal quality. When the bus needs to switch from a dominant state to a recessive state, TLE9371 will first control the switching slope of the bus level. This function not only improves EMC performance but also appropriately reduces the ringing intensity. Within 300ns after this, TLE9371 controls the bus in a low impedance state, thereby completely absorbing the ringing energy.

TLE9371 is easily pin-to-pin compatible with existing DSO8 packaged CAN/CANFD transceivers, allowing customers to easily upgrade the transceiver to solve the ringing problem even if the ringing problem is discovered in the middle and late stages of development. The figure shows the waveform comparison of the same node in the same network topology using ordinary CANFD transceivers and CANSIC transceivers to send 2Mbps CAN signals.

As a major supplier of automotive network solutions in the industry, Infineon has a complete family of CAN transceiver products:

• The communication rate is from 1Mbps to 5Mbps, and with the advent of TLE9371, it is further increased to 8Mbps

• Working modes cover: normal (basic CAN), standby (Standby CAN), sleep (Sleep CAN), local network (PN CAN)

• Product package: 8 pin, 14 pin, DSO package, TSON package

• Temperature grade: grade-1 (-40~125℃), grade-0 (-40~150℃)

CANSIC signal improvement transceiver TLE9371 complements the high bandwidth and ringing suppression part of the product family, which can effectively reduce system design costs and simplify the design difficulty of large networks. This technology ensures effective and reliable transmission of the CANFD protocol from the physical layer without side effects, paving the way for 5Mbps and 8Mbps CANFD applications.

Infineon's TLE9371 series CANSIC transceivers have been mass-produced in the first half of 2023. For detailed technical information and documents, please click to read the original text.

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