SLLU321 July 2022
The TCAN1043AEVM is populated with two 120-Ω power resistors selectable via jumpers between CANH and CANL. 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. The EVM also has footprints for split termination, if needed for the application. Table 2-4 summarizes how to use these termination options. If using split termination, match the resistors. Calculate the CM filter frequency using: fC = 1 / (2πRC). Normally, the split capacitance is in the range of 4.7 nF to 100 nF. Keep in mind, this is the CM filter frequency, not a differential filter that impacts the differential CAN signal directly.
Termination | 120-Ω Resistors | Split Termination Footprints | |||
---|---|---|---|---|---|
Jumper | JMP3 | JMP4 | R9 | R14 | C6 |
No termination | Open | Open | Not available | Not available | Not available |
120-Ω standard termination | Shorted | Open | |||
60-Ω load | Shorted | Shorted | |||
Split termination | Open | Open | 60 Ω | 60 Ω | 4.7 nF |
The EVM also has footprints for various protection schemes to enhance robustness for extreme system-level EMC requirements. Table 2-5 summarizes these options.
Configuration | Footprint Reference | Use Case | Population and Description |
---|---|---|---|
Series resistors or CM choke | R7/R13 or L1 (common footprint) |
Direct CAN transceiver to bus connection | R7 and R13 populated with 0 Ω (default population) |
Series-resistance protection, CAN transceiver to bus connection | R7 and R13 populated with MELF resistor as necessary for harsh EMC environment | ||
CM choke (bus filter) | L1 populated with CM choke to filter noise as necessary for harsh EMC environment | ||
Bus filtering capacitors transient protection | C2/C7 | Bus filter | Filter noise as necessary for harsh EMC environment. Use filter capacitors in combination with L1 CM choke |
Transient protection | C2/C7 or D1 | Transient and ESD protection | To add extra protection for system level transients and ESD protection, TVS diode population option via D1 footprint or varistor population via C2/C7 footprint |