ISL81487IBZ-T

These RS-485/RS-422 devices are “fractional” unit load (UL), BiCMOS, 5V powered, single transceivers that meet both the RS-485 and RS-422 standards for balanced communication. Unlike competitive devices, this family is specified for 10% tolerance supplies (4.5V to 5.5V). The ISL81483 and ISL81487 present a 1/8 unit load to the RS-485 bus, which allows up to 256 transceivers on the network for large node count systems (e.g., process automation, remote meter reading systems). The 1/4 UL ISL8487 allows up to 128 transceivers on the bus. In a remote utility meter reading system, individual (apartments for example) utility meter readings are routed to a concentrator via an RS-485 network, so the high allowed node count minimizes the number of repeaters required to network all the meters. Data for all meters is then read out from the concentrator via a single access port, or a wireless link. Slew rate limited drivers on the ISL8487 and ISL81483 reduce EMI, and minimize reflections from improperly terminated transmission lines, or unterminated stubs in multidrop and multipoint applications. Data rates up to 250kbps are achievable with these devices. Data rates up to 5Mbps are achievable by using the ISL81487, which features higher slew rates. Receiver (R×) inputs feature a “fail-safe if open” design, which ensures a logic high Rx output if Rx inputs are floating. 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. These half duplex devices multiplex the Rx inputs and Tx outputs to allow transceivers with Rx and Tx disable functions in 8 lead packages.

Applications

• High Node Count Networks
• Automated Utility Meter Reading Systems
• Factory Automation
• Security Networks
• Building Environmental Control Systems
• Industrial/Process Control Networks

Key features

• Fractional Unit Load Allows up to 256 Devices on the Bus
• Specified for 10% Tolerance Supplies
• Class 3 ESD Protection (HBM) on all Pins >7kV
• High Data Rate Version (ISL81487) up to 5Mbps
• Slew Rate Limited Versions for Error Free Data Transmission (ISL8487, ISL81483) up to 250kbps
• Low Current Shutdown Mode (Except ISL81487) 0.5μA
• Low Quiescent Supply Current:
• ISL8487, ISL81483 145μA (Max.)
• ISL81487 420μA (Max.)
• -7V to +12V Common Mode Input Voltage Range
• Three State Rx and Tx Outputs
• 30ns Propagation Delays, 5ns Skew (ISL81487)
• Half Duplex Pinouts
• Operate from a Single +5V Supply (10% Tolerance)
• Current Limiting and Thermal Shutdown for Driver Overload Protection
• Drop-In Replacements for: MAX487 (ISL8487); MAX1483 (ISL81483); MAX1487, LMS1487 (ISL81487)
• Pb-Free Plus Anneal Available (RoHS Compliant)