STMicroelectronics’ RS-485 transceivers

Marking the debut of a new series of transceivers from ST, the ST4E1240 aims to provide strong and consistent RS-485 signalling for the demanding industrial sectors of today. These advanced transceivers accommodate data rates significantly exceeding the initial RS-485 standards, facilitating multipoint connections across longer cable distances with the capability to support over 64 transceivers on a single bus. They find application in various fields such as programmable logic controllers (PLCs), robotics, telecom infrastructures, smart-building systems, servo drives, optical networking, grid systems, data-acquisition frameworks including smart meters, and backplane buses.

The ST4E1240's built-in protection complies with IEC 61000-4-2 standards for up to +/-12kV contact discharge, negating the need for external ESD safeguards. Additionally, it provides class-A fast-transient protection up to +/- 4kV in accordance with IEC 61000-4-4, safeguarding data consistency and bus stability. Its hot-swap mechanism averts undesirable bus conditions during power-ups or connections, effectively discharging up to 100pF of parasitic capacitance. The transceiver also features a failsafe mechanism that activates the output high to prevent uncertain states when an open, shorted, or idle bus is detected. Other characteristics include 250mA short-circuit protection and thermal shutdown functionality.

Complying with TIA/EIA-485 (RS-485) standards, the ST4E1240 ensures the output differential voltage surpasses 2.1V, with a 5V supply, making it compatible with the widely-used PROFIBUS field bus standard. An additional shutdown feature, operated via external enable pins, lowers the idle current to below 3.5µA, catering to energy-efficient applications.

The ST4E1240 RS-485 transceiver is included in ST’s 10-year longevity programme, guaranteeing extended product support. Currently in production, the device is available in an SO-8 4.9mm x 3.91mm package, priced at $0.81 for orders of 1,000 units. ST’s eStore is offering free samples.