CAN Transcvr
A CAN transceiver translates a controller's transmit signal into differential bus signalling and returns the detected bus state to the controller. It is the physical interface, not the complete CAN protocol controller. Supply, common-mode, fault protection and supported data rate depend on the chosen device.
For the high-speed CAN bus described by TI, the driver actively establishes the dominant differential state and releases it for the recessive state. Termination helps the differential voltage settle correctly. Place a nominal 120 Ω termination across CANH and CANL at each end of a 120 Ω cable. Optional split termination replaces each end's 120 Ω resistor with two series 60 Ω resistors and a capacitor from their midpoint to ground.
In plain terms
Like a referee who shouts over a stadium crowd by yelling and clapping at once — the dominant state actively pulls both wires apart, so any single node can override an idle bus without permission.
Why designers use it
- Survive automotive electrical hostility — load dumps, jump starts, and 24 V truck systems all sit inside the AEC-Q100 transceiver's −40 °C to +150 °C operating window.
- Multi-master arbitration without a controller — bit-by-bit collision resolution lets the highest-priority node always win, perfect for safety-critical messages like ABS commands.
- Robust noise rejection — the differential signal plus split termination shrugs off the kHz-range BLDC pulses, ignition coil snaps, and alternator whine that swamp single-ended buses.
- Short-circuit and thermal protection — every modern transceiver self-survives a TXD stuck low or a wire shorted to battery without taking the MCU with it.
Best for
- Vehicle bus
- Industrial CANopen
- Robotics
Key specifications
- Physical layer: Select the required CAN variant
- End termination in this example: 120 Ω at each end of a 120 Ω cable
- Split option per end: 60 Ω + 60 Ω in series, midpoint capacitor to ground
- Electrical limits: Exact transceiver datasheet required
When not to use it
- When the device does not support the required CAN mode, data rate, common-mode range or fault conditions.
- As a substitute for the CAN controller and its protocol software.
- With termination copied from a different physical-layer type without checking the network specification.
Common mistakes
- Confusing the two 120 Ω end terminations with one 60 Ω termination at a single end. Two 120 Ω resistors appear as about 60 Ω in parallel in a simple unpowered bus measurement.
- Adding a full termination at every intermediate node instead of the two cable ends.
- Removing a node that also carries an essential end termination.
- Using poorly matched split-termination resistors or insufficient resistor fault-power ratings.
Where you will find it
- A 2024 Ford F-150 hangs roughly 50 ECUs off three CAN-FD buses (powertrain, body, chassis), each ECU using an NXP TJA1462 transceiver: the chip's 5 Mbit/s data-phase support and ±58 V bus fault tolerance lets the truck survive a stray 12 V short during an upfitter's wiring job without bricking the BCM.
- A John Deere 8R-series tractor uses ISOBUS (a CAN-based agricultural standard) over Bosch's TJA1042 transceivers to coordinate the engine, transmission, and a trailing seed-planter from a single touchscreen — the dominant-wins arbitration makes sure a planter's 'stop seeding' command always pre-empts a non-critical telemetry packet.
- An indoor air-quality multimeter from Vaisala's GMP252 line uses Microchip's MCP2562FD transceiver to deliver CO₂ data over a building's CANopen sensor backbone: the chip's standby mode drops the receiver to <10 µA so the battery-powered node lasts two years between service intervals.
A short history
TI's CAN termination guide compares standard and split termination and shows why removing an end termination can cause bit errors. Split termination adds common-mode filtering, but matched resistors and suitable fault-power ratings are important. This guidance describes a high-speed CAN arrangement, not every network marketed under the CAN name.
Good to know
- Split termination changes the common-mode filtering without changing the nominal 120 Ω differential termination at that end.
- The resistor-power calculation should include possible bus faults, not only normal signalling.