ISL4491E

The ISL4489E and ISL4491E are ESD protected, “fractional”Unit Load (UL), BiCMOS, 5V powered, single transceivers that meet both the RS-485 and RS-422 standards for balanced communication. Each driver output and receiver input is protected against ±15kV ESD strikes without latch-up. Unlike competitive versions, these devices are specified for 10% tolerance supplies (4. 5V to 5. 5V). The Rx inputs and Tx outputs present a 1/8 unit load to the RS-485 bus, which allows a total of 256 transmitters and receivers on the network for large node count systems. These devices are configured for full duplex (separate Rx input and Tx output pins) applications, so they are ideal for RS-422 networks requiring high ESD tolerance on the bus pins. The ISL4489E uses a slew rate limited driver that reduces EMI and minimizes reflections from improperly terminated transmission lines, or unterminated stubs in multidrop and multipoint applications. Data rates up to 15Mbps are achievable using the ISL4491E, which features higher slew rates. The receiver (Rx) inputs feature a “fail-safe if open” design, which ensures a logic high Rx output if Rx inputs are floating. The driver (Tx) outputs are short-circuit protected, even for voltages exceeding the power supply voltage. Additionally, on-chip thermal shutdown circuitry disables the Tx outputs to prevent damage if power dissipation becomes excessive.