TJA1050 High-Speed CAN Transceiver

The TJA1050 is the interface between the CAN protocol controller and the physical bus. It is primarily intended for high-speed automotive applications using baud rates from 40 baud up to 1 Mbaud. It provides differential transmit capability to the bus and differential receiver capability to the CAN protocol controller. A current-limiting circuit protects the transmitter output stage from damage caused by accidental short-circuit to either positive or negative battery voltage, although power dissipation increases during this fault condition. A thermal protection circuit protects the IC from damage by switching off the transmitter if the junction temperature exceeds a value of approximately 165 °C. The CANH and CANL lines are protected from automotive electrical transients (according to ISO 7637) and are also protected from Electro-Static-Discharge (ESD) of up to 4 kV from the human body.

Control line S (pin 8) allows two operating modes to be selected; high-speed mode or silent mode. High-speed mode is the normal operating mode and is selected by connecting pin S to the ground. It is the default mode if pin S is unconnected. In the silent mode, the transmitter is disabled. All other IC functions continue to operate. The silent mode is selected by connecting pin S to VCC. A ‘TXD Dominant Time-out’ timer circuit prevents the bus lines from being driven to a permanent dominant state (blocking all network communication) if TXD is forced permanently LOW by a hardware and/or software application failure. The timer is triggered by a negative edge on TXD. If the duration of the LOW-level on TXD exceeds the internal timer value, the transmitter is disabled, driving the bus into a recessive state. The timer is reset by a positive edge on TXD.