The CAN physical layer is a dual-wire bus with a VCC/2 related recessive level. Smooth output wave shaping is very important. Electromagnetic emission (EME) mainly depends on the falling and rising edge of the CAN bus waveforms. Smooth edges reduce the EME. For the PCB layout it is recommended to keep the same dimensions and lengths for all bus wire connections from the transceiver to the common mode choke (CMC) and/or termination. Usage of common mode choke and type of termination depend on the application and OEM requirements.
The common mode choke is the first interference suppression in CAN in order to reduce EME. It attenuates noise which is common to CANH and CANL. A CMC increases the common mode rejection ratio (CMRR) and provides high impedance for common signals, when the bus is in recessive state. Additionally the CMC provides low impedance for differential signals, when the bus is in dominant state. The CMC dampens differential mode interference, which may be injected by split termination. The inductance of the common mode choke should be as low as possible in order to avoid high shutdown peaks.
For HS CAN applications it is recommended to use stabilization capacitors at VCC voltage supply input and VIO reference supply input in order to support the robust performance of the CAN transceiver. It is important to place the stabilization capacitors C1 and C2 as close as possible to the VCC and VIO pins. The recommended value for the stabilization capacitor of the voltage supply VCC and the reference voltage VIO is in the range of 47 nF to 100 nF. Due to their low ESR and low inductance compared to other capacitor types, it is recommended to use ceramic capacitors.

Consider the following rules to achieve best performance of the transceiver and the ECU:
• It is recommended to place the transceiver as close as possible to the ECU connector in order to minimize track length of bus lines
• TxD and RxD connections to microcontroller should be as short as possible
• Place two individual 100 nF capacitors close to the VCC and VIO pins. Due to their low ESR and low
inductance compared to other capacitor types, it is recommended to use ceramic capacitors
• In case a CMC (common mode choke) is used, place it as close as possible to the transceiver bus pin CANH and CANL
• Avoid routing CANH and CANL in parallel to fast-switching signals or off-board signals in order to reduce noise injection to the bus
• Avoid routing digital signals in parallel to CANH and CANL
• CANH and CANL tracks should have the same length. They should be routed symmetrically close together with smooth edges
• For high current applications the current should not flow through the GND line of transceiver and
microcontroller in series
• Use same dimensions and lengths for all wire connections from the transceiver to the CMC and/or
termination
• Avoid routing transceiver GND and microcontroller GND in series. The GND connector should be placed as close as possible to the transceiver