Texas Instruments SN65HVD257, User Manual

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SN65HVD257 EVM Setup and Operation for Redundant (Parallel Networks)
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3.3 Using CAN Bus Protection and Filtering Configuration
The EVM also has component footprints for various protection schemes to enhance robustness for
extreme system-level EMC requirements.
Table 4 summarizes these options. Typical examples of for
these components are: CM choke (TDK ACT45B series and EPCOS B82789 series from 11µH to 100µH),
bus filter capacitors are typically 100pF or less, TVS diodes from the MMBZ series 27V or lower, varistors
such as the TDK AVR series).
Table 4. CAN Bus Protection and Filtering Configuration
Protection and Filtering Footprint
Use Case Population and Description
Bus 1 Reference
Direct CAN transceiver to bus R7 and R11 populated with 0 Ω (default
connection population)
Series Resistors or R7 and R11 or L1 Series resistance protection CAN R7 and R11 populated with MELF resistor
Common Mode Choke (common footprint) transceiver to bus connection as necessary for harsh EMC environment
L1 populated with CM choke to filter noise
CM choke (bus filter)
as necessary for harsh EMC environment
Filter noise as necessary for harsh EMC
Bus Filtering Caps C2 and C5 Bus filter environment. Filter caps may be used in
combination with L1 CM choke.
To add extra protection for system level
transients and ESD protection, use the
D1 and D2,
Transient Protection Transient & ESD Protection population option footprints D1 and D2 for
C2 and C7 or D7
TVS diodes, or C2 and C7 or D7 for
varistors.
Protection and Filtering Footprint
Use Case Population and Description
Bus 2 Reference
Direct CAN transceiver to bus R31 and R35 populated with 0 Ω (default
connection population)
Series Resistors or R31 and R35 or L2 Series resistance protection CAN R31 and R35 populated with MELF resistor
Common Mode Choke (common footprint) transceiver to bus connection as necessary for harsh EMC environment
L2 populated with CM choke to filter noise
CM choke (bus filter)
as necessary for harsh EMC environment
Filter noise as necessary for harsh EMC
Bus Filtering Caps C22 and C25 Bus filter environment. Filter caps may be used in
combination with L2 CM choke.
To add extra protection for system level
transients and ESD protection, use the
D4 and D5,
Transient Protection Transient & ESD Protection population option footprints D4 and D5 for
C22 and C25 or D6
TVS diodes or C22 and C25 or D6 for
varistors.
10 SN65HVD257 CAN EVM: Functional Safety and Redundant CAN Network SLLU172 – August 2012
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