The ST490A is a low power transceiver for RS485 and RS-422 communications. The device contains one driver and one receiver in full duplex configuration. The ST490A draws 5mA (typ.) of supply current when unloaded or fully loaded with disabled drivers. It operates from a single 5V supply. Driver is short-circuit current limited and is protected against excessive power dissipation by thermal shutdown circuitry that place the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic high output if both inputs are open circuit.