TCAN1146-Q1: TCAN1146: Supporting CAN FD and Partial networking is being used in Gateway application

Manoj,

Can you elaborate on the questions the customer has about partial networking? To start, if they want to use partial networking fully, all nodes on the bus will need to have transceivers with the selective wake feature. Selective wake can only be used with Classic CAN protocol, it does not work with CAN FD and there aren't any transceivers on the market with CAN FD + partial networking available. TI's selective wake transceivers also have the ability to be on the same bus as CAN FD, and can be configured to ignore CAN FD messages.

There is more information if you go to TI.com, go to the TCAN1145-Q1 or TCAN1146-Q1 product folder, and look at design support. Application notes and an EVM are available. Again though, please try to find what specific questions the customer has and we can address them.

Regards,

Eric Hackett 

Hi Eric,

Can we continue our discussion on mail. IFor 5 Mbps transmission,  need information like oscillator requirement. EMC Capacitor, Common mode choke, CAN connector pin current requirement, contact resistance, Transciver driver summary,  Transciver Tx and Rx drivery symmetery. Node internal delay time, CAN FD(5Mbps) waveform. Rise and fall time, CAN FD bit timing parameter

Manoj,

I'd like to keep this on E2E, and several of the parameters you listed are agnostic to the transceiver, and more about the physical layout of the CAN bus and the delays associated. Others are listed in the datasheet, and we can help with CMC and filter capacitor suggestions. Can you get more information on the expected number of nodes, and physical length of the CAN bus?

For filter capacitance, we recommend 10pF - 100pF (depending on the number of nodes) on both CANH and CANL to GND. For the CMC, TDK and Coilcraft both have great families of devices, and typical values at 51uH or 100uH with 200mA current rating. CAN connector current requirement and contact resistance is not necessarily in our realm of expertise, but we can still help based on experience with other customers.

Regards,

Eric Hackett 

Hi Eric, 

for 5 mbps. Expected number of node is around 10. Length is around 4 to 5 meter. We need to udnerstand the CAN bus phsyicallayout in vehcile. It should be single line bus topology. What should be stub length for node etc..

Regards

Manoj A

Manoj,

Thanks for the extra information, 5Mbps at 4-5 meters won't present problems on its own, but you are correct about stub length. With 10 nodes, stub length will be critical to mitigate the impedance mismatch and thus the potential ringing that can occur due to signal reflections. The general rule of thumb is for stub length to be at longest 0.3 * full length of the CAN bus, and with higher data rates that number gets smaller. For this application, I wouldn't recommend more than 1m stub length, and if possible 0.5m at the longest. 

The node internal delay time, and CAN FD bit timing parameters will need to be first calculated by the transceiver loop delay and other added delay due to bus components, then configured based on the data rate being used. The parameters you have listed, like transceiver driver symmetry, and others that you'll need like propagation delay, loop delay time, and rise and fall times, can all be found in the Electrical Parameters section of the datasheet. Once calculated, real-time testing will also need to be done to validate the configurations, which will likely need to be further adjusted.

And to clarify my first reply, TCAN1146-Q1 is capable of CAN FD communication up to 8Mbps, but the selective wake feature is not available for CAN FD CAN frames. 

Regards,

Eric Hackett