The ADM2491E is an isolated data transceiver with ±8 kV ESD protection and is suitable for high speed， half- or full-duplex communication on multipoint transmission lines. For halfduplex operation， the transmitter outputs and the receiver inputs share the same transmission line. Transmitter output Pin Y is linked externally to receiver input Pin A， and transmitter output Pin Z is linked to receiver input Pin B. The ADM2491E is designed for balanced transmission lines and complies with ANSI TIA/EIA RS-485-A-1998 and ISO 8482： 1987（E）。 The device employs Analog Devices， Inc.， iCoupler? technology to combine a 3-channel isolator， a threestate differential line driver， and a differential input receiver into a single package. The differential transmitter outputs and receiver inputs feature electrostatic discharge circuitry that provides protection to ±8 kV using the human body model （HBM）。 The logic side of the device can be powered with either a 5 V or a 3.3 V supply， whereas the bus side requires an isolated 5 V supply. The device has current-limiting and thermal shutdown features to protect against output short circuits and situations in which bus contention could cause excessive power dissipation. The ADM2491E is available in a wide body， 16-lead SOIC package and operates over the ?40°C to +85°C temperature range.