Texas Instruments TLIN2029-Q1, User Manual

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TCA N455 0
Optiona l
Commo n Mod e
Choke Pad
(Replace 0 Ÿ
Resistors)
CAN B us
Termination
and conne ction
Jumpers
Optiona l TVS
Diode
CAN bu s DB-9
Wiring Harness
Conne ctor
(CANH/CANL,
Gro und, VBA T
and LIN)
CAN B us
Sign al Hea der
40 MHz
Crystal
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Hardware description
7 SLLU216 – July 2019
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SPI to CAN FD SBC + LIN Transceiver BoosterPack User's Guide
2.2 CAN
The following sections describe the features of the CAN bus.
Figure 3. CAN bus components and features
2.2.1 CAN Bus DB-9 Connector (J7)
The CAN bus signals CANH and CANL are accessible through the DB-9 connector J7, which follows the
industry-standard pin mapping. This mapping allows for easy integration into an existing system. The
external supply voltage V
BAT
, ground, and connector shield ground connections are also included in the
connector J7.
2.2.2 CAN Bus Signal Header (J8)
The CAN bus signals are also available on header J8. This may be more convenient in a lab environment
or to attach scope probes to monitor the bus connected the EVM through the DB-9 connector.
2.2.3 CAN TVS Diode (D8)
A TVS diode footprint has been added to the BoosterPack and diodes installed to provide maximum
protection when used in environments that may not have proper ESD controls. However, the use of these
external diodes are considered optional and the TCAN4550-Q1 contains robust internal ESD protection.
2.2.4 Termination
The CAN standard requires termination of the CAN bus at each end with 120
Ω
of resistance between the
CANH and CANL pins. A common technique, also used on this BoosterPack, is to implement a split
termination using two 60-
Ω
resistors in series and a 4.7-nF capacitor to ground. The capacitor to ground
provides a path for filtering common-mode noise out of the signals that can come from sources such as
asymmetry between the CANH and CANL signals. Common-mode noise is a result of unequal lengths
between the CANH and CANL wires, asymmetrical bus loading, or other sources. If the BoosterPack is
used in a lab environment or as one of the end nodes of the CAN bus, the termination can be enabled by
placing shunts on jumpers J6 and J9 to connect the termination resistors to the CANH and CANL lines.
However, if the BoosterPack is used on a bus with existing termination resistors, or does not require local
termination, removing the shunts on J6 and J9 disconnects the local termination from the CANH and
CANL lines.