RS-485/RS-422 family of transceivers delivers the highest noise immunity and ESD protection in small packages

The family’s higher output voltage (2.4V min.) is 60% larger than the 1.5V required by the RS-485 standard, providing the advantage of nearly 1V greater noise immunity and the ability to drive longer cable lengths, resulting in a more robust serial communication system.

The unique combination of high ESD protection and increased output drive give designers of high-performance industrial applications a new level of system reliability. Combining the tiny MSOP package option will enable smaller PCB designs or additional features in the same area.

The ISL315XE family is made up of BiCMOS, IEC61000 ESD-protected, 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 ±16.5kV ESD strikes without latch-up.

The ISL315XE transmitters all deliver exceptional differential output voltages (2.4V min), into the RS-485 required 54 Ohm load, for better noise immunity or to allow up to eight 120 Ohm terminations in ‘star’ or other non-standard bus topologies. These transmitters deliver RS-485 compliant levels (1.5V) even with eight termination resistors. Unlike competing devices that require up to 15mA quiescent supply currents, the ISL315XE family requires only 800uA (maximum). Power consumption is further reduced via a low-power shutdown feature that reduces Icc to 70nA when the driver and receiver are both disabled.

The devices have very low bus currents, so they provide a true 1/8 unit load to the RS-485 bus. This allows up to 256 transceivers on the network without violating the RS-485 specification’s 32-unit load maximum and without using repeaters.

Receiver (Rx) inputs feature a ‘full fail-safe’ design, which ensures a logic high Rx output if Rx inputs are floating, shorted, or on a terminated but undriven bus. Rx outputs feature high drive levels – typically 28mA @ VOL = 1V – to ease the design of optocoupled isolated interfaces.

The ISL3150E, ISL3152E, ISL3153E and ISL3155E utilise slew-rate-limited drivers which reduce EMI and minimise reflections from improperly terminated transmission lines, or unterminated stubs in multidrop and multipoint applications. The ISL3156 and ISL3158 are rated up to 20Mbps data rate for high-speed applications.

Hot plug circuitry ensures that the Tx and Rx outputs remain in a high impedance state until the power supply has stabilised. The Tx outputs have full short circuit protection.
The ISL3150E, ISL3153E, ISL3156E are configured for full duplex (e.g., RS-422) applications. The half duplex versions multiplex the Rx inputs and Tx outputs to allow transceivers with output disable functions in 8-lead packages.

Other key features of the family include class 3 ESD level on all other pins >7kV HBM, specified for single 5V, 10% tolerance supplies, and a -7V to +12V common mode input voltage range. Target applications include utility meters and automated meter reading systems, high node count systems and networks requiring more than two termination resistors, PROFIBUS® and field bus networks, and factory automation, security camera networks, building lighting and environmental control systems, and industrial/process control networks.

The ISL315XE family is available now in 8-lead MSOP, 8-lead SOIC, 10-lead MSOP and 14-lead SOIC packages.