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 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 resistors, R2 and
R3, with the center or split tap of the
termination connected to ground via capacitor C3.
Split termination provides common mode filtering
for the bus. See Section 8.2.1.1, and Section 7.3.4 for information on termination
concepts and power ratings needed for the
termination resistor(s).