Automotive Ethernet may be the darling for self-driving cars and high-speed sensors like radar and cameras. However, for most chores like body control management, the CAN bus is still a major player because of its robustness and synchronization support. Unfortunately, its speed and data packet limitations are well-known. CAN FD addresses both of these issues, providing 5-Mbit/s throughput and a larger packet size.
Many new microcontrollers have CAN controllers that support CAN and CAN FD. CAN and CAN FD don’t play well together, so a network needs to use one or the other. Micros with CAN controllers that don’t support CAN FD require external support like Texas Instruments’ new TCAN4550-Q1.
The TCAN4550-Q1 supports CAN FD’s 5-Mbit/s data rate and 64-byte packets in a 4.5- by 3.5-mm, 20-pin QFN package. This includes the CAN FD buffers providing a single-chip solution. It hooks into a host microcontroller using SPI, which allows for expansion of a micro’s CAN controller options. It can also be used to augment an existing CAN network (Fig. 1), enabling control of legacy CAN networks as well as newer, faster CAN FD networks. A micro with multiple CAN/CAN FD interfaces could act as a network gateway.
1. CAN and CAN FD devices can’t be connected to the same network, but they are able to operate in parallel. Likewise, a host can act as a gateway between networks.
The chip has a 70-mA LDO regulator on-chip along with a watchdog timer and failsafe power modes. These failsafe modes are handy if the microprocessor should fail to properly power down. The TCAN4550-Q1 also handles 3.3- and 5-V I/Os. AEC-Q1000 CAN transceivers provide 5-kVrms galvanic isolation with 70-V bus fault protection.
The TCAN4550-Q1 also supports a faster 8-Mbit/s speed that’s currently not part of the standard. On the plus side, the faster data rate may significantly reduce the time to download an over-the-air update to CAN FD devices equipped with a TCAN4550-Q1.
2. The TCAN4550-Q1 evaluation module is designed to interface with a microcontroller’s SPI port.
An evaluation module (Fig. 2) is designed to get developers up and running quickly. The SPI interface works with most microcontrollers.
