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 an 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 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 capacitors must 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, not the path of least resistance.
This layout example shows how to implement split
termination on the CAN node. The termination is split into two resistors, R4 and R5, with
the center or split tap of the termination connected to ground through capacitor C3. Split
termination provides common-mode filtering for the bus. See CAN Termination, CAN Bus Short Circuit Current Limiting, and Equation 2 for information on termination concepts and required power rating for the termination
resistors.