TCAN1042-Q1: About the TCAN1042 Q1 on the PCB Location

Qinlei,

If the choices are closer to the MCU or closer to the connector, closer to the MCU would be better. This is because most of the noise and transients are coming from outside the local CAN system, and placing the IC close to the connector would reduce the ability for protective components to protect the device. 

Placing the transceiver close to the MCU has the chance to introduce noise from the transceiver, but the only direct connection to the transceiver from the MCU and vice versa are the logic pins. The majority (if not all) noise generated by the transceiver comes from the CAN bus, and is propagated through as such. With proper layout techniques and filtering, the noise from the CAN bus will rarely have a significant enough effect on the MCU to cause miscommunication, unwanted resets, or other phenomenon where noise is interfering. Putting a ground copper pour in the 'free' PCB space between the MCU and transceiver is recommended to help with noise, as well as properly decoupling the supply pins, and filtering any signals going into the MCU from the transceiver.

In short, the risk for noise from the CAN transceiver to the MCU is not great enough to place the transceiver close to the connector. Please let us know if you have more questions.

Regards,

Eric Hackett