Texas Instruments TCAN1046V, Руководство пользователя

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EVM Setup and Operation
7 SLLU296 – August 2018
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Copyright © 2018, Texas Instruments Incorporated
TCAN1046V Evaluation Module
2.2 Using CAN Bus Load, Termination, and Protection Configurations
The TCAN1046V EVM has several bus termination options for both available buses. The termination on
the CAN bus (CANH and CANL) can be configured with the J2 and J3 (CAN1) or J6 and J8 (CAN2)
jumpers. Each jumper adds 120-
Ω termination to the respective bus. When using one resistor, the EVM is
used as a terminated end of a bus. For electrical measurements to represent the total loading of the bus,
use both 120-
Ω resistors in parallel to give the standard 60- Ω load for parametric measurement. Split
termination is also available and populated on both buses, and can be removed with some simple solder
work.
Table 3 summarizes how to use these termination options. If using split termination, match the
resistors. Calculate the common mode filter frequency using: f
C
= 1 / (2
π
RC). Normally, the split
capacitance is in the range of 4.7 nF to 100 nF. Keep in mind this is the common-mode filter frequency,
not a differential filter that impacts the differential CAN signal directly.
Table 3. Bus Termination Configuration
Termination
Configuration
120- Ω Resistors
(CAN1)
120- Ω Resistors
(CAN2)
Split Termination
Footprints
(CAN1)
Split Termination
Footprints
(CAN2)
Split
Terminati
on
Footprints
(CAN1)
Split
Terminati
on
Footprints
(CAN2)
J2 J3 J6 J8 R3 R7 R15 R21 C3 C12
Standard
termination (120 Ω )
shorted open
N/A N/A N/A
60- Ω load -
electrical
parameterics
shorted shorted
Split termination
(common mode
stabilization)
open open 60 Ω 60 Ω populated
The EVM also has footprints for various protection schemes to enhance robustness for extreme system-
level EMC requirements.
Table 4 summarizes these options.
Table 4. Protection and Filtering Configuration
Configuration Footprint Reference Use Case Population and Description
Series resistors or common
mode choke
R1/R9 or L1 (common
footprint)
Direct CAN1 transceiver to bus
connection
R1 and R9 populated with 0 Ω
Series resistance protection,
CAN1 transceiver to bus
connection R1and R9 populated with MELF
resistor as necessary for harsh
EMC environment
CM choke (CAN1 bus filter)
L1 populated with CM choke to
filter noise as necessary for harsh
EMC environment (default
population)
R11/R25 or L2 (common
footprint)
Direct CAN2 transceiver to bus
connection
R11 and R25 populated with 0 Ω
Series resistance protection,
CAN2 transceiver to bus
connection R11 and R25 populated with MELF
resistor as necessary for harsh
EMC environment
CM choke (CAN2 bus filter)
L1 populated with CM choke to
filter noise as necessary for harsh
EMC environment (default
population)
Bus filtering caps transient
protection
C1/C6
Bus filter
Filter noise as necessary for harsh
EMC environment. Use filter caps
in combination with L1 CM choke.
C9/C15
Filter noise as necessary for harsh
EMC environment. Use filter caps
in combination with L2 CM choke.