ST3085N 500kbps ±24kV ESD Polarity-Auto-Detect RS-485 Transceiver

Overview

The ST3085N is a +5V half-duplex RS-485 transceiver with automatic bus-polarity adaptation. Its on-chip polarity correction circuit detects and corrects bus polarity within an 80ms detection window, automatically adapting to the bus port polarity in RS-485 communication systems — communication continues even when the A/B lines are wired in reverse, significantly reducing installation and commissioning effort. Integrated TVS protection diodes better resist transient noise coupled onto the bus, and the bus pins provide ESD protection up to ±24kV per IEC 61000-4-2 contact discharge. A slew-rate-limited driver significantly reduces EMI and reflections caused by improperly terminated cables, supporting error-free data transmission up to 500kbps. Built-in fail-safe circuitry keeps the receiver output logic-high when the receiver inputs are open or shorted, and a 1/8 unit-load receiver input impedance allows up to 256 transceivers on a single bus for half-duplex communication. Offered in an SOP-8 package over a -40~+85℃ operating temperature range, the ST3085N provides a polarity-worry-free RS-485 interface for smart meters, data acquisition terminals and industrial control applications.

Features

• Single +5V supply operation
• Automatic bus polarity detection and correction, 80ms detection window
• On-chip TVS protection diodes against bus transient noise
• Bus I/O ESD protection: ±24kV IEC 61000-4-2 contact discharge
• Max data rate: 500kbps; slew-rate-limited driver reduces EMI and reflections
• Built-in fail-safe circuit: logic-high output on open/shorted inputs
• 1/8 unit-load input impedance allows up to 256 transceivers on the bus
• SOP-8 package

Typical Applications

• Smart electricity meters
• Data acquisition terminals
• Industrial control
• Security and surveillance systems