Isolated RS-485 transceiver

Louise Davis

Intersil Corporation has announced the industry’s smallest isolated RS-485 differential bus transceiver designed to provide 4Mbps bidirectional data transmission for Industrial Internet of Things (IIoT) networks.

The high-speed ISL32704E delivers industry-leading electromagnetic interference (EMI) and common-mode transient immunity (CMTI) in a small 4mm x 5mm QSOP package that is 70% smaller than competitive devices. It also provides 600VRMS of working voltage, which is approximately 50% higher than the closest competitor.

The ISL32704E RS-485 transceiver leverages giant magnetoresistance (GMR) technology to provide galvanic isolation that keeps the communication bus free from common-mode noise generated in electrically noisy factory and building automation environments.

The ISL32704E is suited for the equipment-to-bus interface in IIoT networks that connect programmable logic controllers (PLCs) to instruments, robots, motor drives, data acquisition and digital I/O modules.

The advantage of Intersil’s ISL32704E GMR isolation over other isolation technologies is its low radiated emission and low EMI susceptibility. In addition, its GMR isolation does not require the elaborate encoding schemes found in capacitive and transformer-based isolators that use RF carriers or pulse-width modulation (PWM) to transfer DC and low frequency signals across the barrier.

The ISL32704E also offers 80% less power consumption than competing devices because it doesn’t use current hungry power transfer coils or transformers. Its 20mA supply current allows the ISL32704E to operate in a tiny QSOP package at maximum speed without overheating.

On the non-isolated control-side, the ISL32704E supports direct connection to a 3V microcontroller while the isolated bus-side connects to a higher voltage 5V supply for communication of strong bus signals across 100 meters and longer distances. The ISL32704E is fully compliant with the EN 50081 and EN 50082-2 electromagnetic compatibility (EMC) standards and the umbrella line-voltage standard for information technology equipment (ITE) EN 61000.