SN65HVD257: Another CAN Transceiver with Functional Safety

Monisha,

Thanks for bringing these questions to E2E.

1. This device actually isn't rated for functional safety. That wording in the datasheet is leftover from when it was first written and is just saying that the redundant topology can help with safety-related applications. The only CAN devices fully released and in our portfolio that are functionally safety capable are the TCAN4550-Q1 and the TCAN1145-Q1.

2. No, this device does not support functional safety.

3. This just means that because of the fault output on the SN65HVD257, the transceiver can be configured in a redundant topology that will communicate to the MCU when the CAN bus is stuck. At this point, the MCU can swap to the other transceiver in the redundant setup. This does not mean that the device is approved for functional safety at the TI level. This is a typo in the datasheet and it will be corrected asap.

TI's CAN transceivers can assist in achieving ASIL ratings at the system level, but at the transceiver level they do not have any ASIL rating.

Regards,

Hi Eric,

Thanks for your response. This was helpful.

I have some more queries.

1.TI's CAN transceivers can assist in achieving ASIL ratings at the system level. so while using SN65HVD257 is it possible to acheive the SIL certification in product level?

2.My application is to use CAN Reduntant topology along with Safety function. So can I use TCAN4550-Q1 and  TCAN1145-Q1 as an alternate for SN65HVD257? Is there any issue?

3. If any CAN transceiver having fault output is useful for reduntant topology?

4. For TCAN4550-Q1 and  TCAN1145-Q1 uses SPI and UART. What is the use the SPI? Shall i make this pins floating while using?

Warm regards,

Monisha OM

Monisha,

1. Do you mean SIL certification for the transceiver itself? No, this won't be possible. But if you mean the end product, then yes some of our CAN transceivers can aid in ASIL ratings with the right documentation. For the SN65HVD257 device I don't believe we have that documentation available at the moment.

2. The TCAN4550-Q1 and TCAN1145-Q1 are definitely overkill for a socket that is using the SN65HVD257, I was just referencing those devices as CAN devices that are qualified functionally-safety capable within TI. Meaning there is a lot of documentation and a specific qualification process used when developing those parts.

3. Yes, the idea here is that the fault output will immediately notify the MCU if the bus is stuck or has another condition distorting communication, so the MCU can swap to the other CAN transceiver rather than hanging. CAN protocol also has error handling built in to the controllers though, so this can also be used to determine a faulty CAN bus: communication errors begin to pop up.

4. TCAN4550-Q1 is a SPI-to-CAN controller + transceiver integrated into one package. It is meant to be a smoother upgrade path to CAN FD from classic CAN. Rather than buying a dedicated CAN FD controller or an expensive MCU with CAN FD integrated, the user can keep their old MCU and configure the TCAN4550-Q1 through SPI to work as a controller and transceiver in one package. The TCAN1145-Q1 is a partial networking CAN transceiver, using specific wake-up frames to wake specific nodes rather than just a wake-up pulse to wake up all CAN nodes on the bus. As I said, both of these devices are likely overkill for what you are intending, and even if you do decide to use them, the SPI pins are absolutely necessary for their function.

Another device that could work for this is the TCAN1043-Q1 with it's fault output, or the TCAN1046-Q1 as a dual CAN transceiver in one package. 

Please let me know if you have any other questions.

Regards,