Part identity and function
The Maxim Integrated MAX491ECSD+ is a full-duplex transceiver in a 14-SOIC surface-mount package. It integrates one driver and one receiver, operates from a 4.75 V to 5.25 V supply, and is rated for 0°C to 70°C. The 70 mV receiver hysteresis improves noise margin, and the 2.5 Mbps data rate supports most industrial serial links.
Full duplex means the MAX491 can transmit and receive simultaneously over a four-wire RS-422 bus (or a two-pair RS-485 network with separate enable control). The 2.5 Mbps data rate is typical for building-automation gateways, PLC-to-drive links, and multi-drop sensor networks where the cable run stays under about 400 m. At this speed the driver slew rate is fast enough that stub lengths on the bus should be kept under 30 cm to avoid reflections.