Smallest isolated RS-485 transceiver IC

February 14, 2017 // By Graham Prophet
The ISL32704E offers performance, lowest EMI and optimum CMTI, and the highest working voltage for industrial IoT networks

Intersil claims the smallest isolated RS-485 differential bus transceiver, designed to provide 4 Mbps bidirectional data transmission, for Industrial Internet of Things (IIoT) networks. It delivers minimal levels of electromagnetic interference (EMI) and has highest common-mode transient immunity (CMTI) in a 4 x 5 mm QSOP package that is 70% smaller than alternative devices. It also provides 600 VRMS of working voltage, which is approximately 50% higher than the closest competitor. The RS-485 transceiver uses 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 IC 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 device also offers 80% less power consumption than alternative devices because it doesn’t use power transfer coils or transformers. Its 20 mA supply current allows the ISL32704E to operate in a QSOP package at maximum speed without overheating. On the non-isolated control-side, the IC 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 100m 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. “Our new ISL32704E isolated RS-485 transceiver generates virtually no radiated EMI, solving one of the biggest problems customers experience with their industrial designs,” said Philip Chesley, senior vice president of Precision Products at Intersil. “In addition to not requiring any shielding, this transceiver simplifies PCB layout, uses less board space, and enhances data transmission reliability and integrity.”


In a 4 x 5 mm, 16-lead QSOP package it is priced at $3.79 (1000). An ISL32704EVAL1Z evaluation board is $99.




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