CAN FD transceiver
ON Semiconductors has launched the NCV7351F transceiver, which complies with ISO 11898-2:2016. It is qualified for bit-rates up to 5 Mbit/s.
The NCV7351 series of CAN transceiver chips can be used in both 12-V and 24-V systems. These products complement the company’s NCV734x CAN stand−alone transceivers and previous generations such as AMIS42665, AMIS3066x, etc. The NCV7351F version meets the bit-timing symmetry requirements as specified in ISO 11898-2 standard. Due to the common−mode voltage range of the receiver inputs (-30 V to +35 V) and other design features, the transceiver is able to reach outstanding levels of electromagnetic susceptibility (EMS). Similarly, low-electromagnetic emission (EME) is achieved by the matching of the output signals according to the chip provider. The transceiver can be connected to 5-V and 3-V micro-controllers.
The transceiver features a TxD time-out function. The bus-pins are short circuit-protected and protected against 15-kV ESD pulses as well as against transients. Thermal protection is provided, too. The AEC-Q100 qualification makes the chip suitable for automotive applications. It is also intended for industrial usage.
In the normal mode, the transceiver is able to communicate via the bus lines. The signals are transmitted and received to the CAN controller via the pins TxD and RxD. The slopes on the bus lines outputs are optimized to give low EME. In the silent mode, the transmitter is disabled. The bus pins are in recessive state independent of the TxD input. The chip listens to the bus and provides data to controller, but controller is prevented from sending any data to the bus. In off mode, the complete transceiver is disabled and consumes very low current. The CAN pins are floating not loading the CAN network lines.
A thermal protection circuit protects the integrated circuit (IC) from damage by switching off the transmitter, when the junction temperature exceeds a value of approximately 180 °C. Because the transmitter dissipates most of the power, the power dissipation and temperature of the IC is reduced. All other functions continue to operate. The transmitter off-state resets when the temperature decreases below the shutdown threshold and pin TxD goes high.
The TxD dominant time-out timer circuit prevents the bus lines being driven to a permanent dominant state (blocking all network communication), when pin TxD is forced permanently low by a hardware and/or software application failure. The timer is triggered by a negative edge on pin TxD. When the duration of the low-level on pin TxD exceeds the internal timer value tdom, the transmitter is disabled, driving the bus into a recessive state. The timer is reset by a positive edge on pin TxD. This TxD dominant time-out time (tdom(TxD)) defines the minimum possible bit rate to 12 kbit/s.
A current−limiting circuit protects the transmitter output stage from damage caused by accidental short circuit to either positive or negative supply voltage, although power dissipation increases during this fault condition. The CAN_H and CAN_L pins are protected from automotive electrical transients (according to ISO 7634).
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