Place the protection and filtering circuitry
close to the bus connector, J1, to prevent transients, ESD, and noise from
propagating onto the board. This layout example shows a optional transient
voltage suppression (TVS) diode, D1, which may be implemented if the
system-level requirements exceed the specified rating of the transceiver. This
example also shows optional bus filter 0.1μF capacitors C4 and C5.
Design the bus protection components in the direction of the signal path. Do not force the transient current to divert from the signal path to reach the protection device.
Decoupling 0.1μF capacitors should be placed as
close as possible to the supply pins VCC and VIO of
transceiver.
Use at least two vias for supply and ground connections of bypass capacitors and protection devices to minimize trace and via inductance.
Note:
High frequency current follows the path of least impedance and not the path of least resistance.
This layout example shows how split termination
could be implemented on the CAN node. The termination is split into two 60Ω
resistors, R4 and R5, with the center or split tap of the termination connected
to ground via a 1-100nF capacitor C3. Split termination provides common-mode
filtering for the bus. See CAN Termination, CAN Bus Short Circuit Current Limiting, and 2 for information on termination concepts and power ratings needed for the
termination resistor(s).