Isolated RS422/RS485 transceiver with on-board power
The Analog Devices LTM2881HY-3#PBF is a µModule isolated RS422/RS485 transceiver that integrates a magnetic-coupled digital isolator and an isolated DC/DC converter in a single 32-BBGA package. It supports data rates up to 20 Mbps and provides 2500 Vrms of galvanic isolation between the bus side and the logic side. The part is designed for industrial communication links where ground loops, common-mode voltages, and noise require a robust isolation barrier. The integrated isolated power supply means the bus side does not need a separate isolated DC/DC converter, saving board space and simplifying the power architecture.
The 20 Mbps data rate covers most industrial fieldbus speeds — Profibus DP (12 Mbps), Modbus RTU (up to 10 Mbps with short cable runs), and RS422 point-to-point links. If your application only needs 115.2 kbps, this part still works, but a lower-speed isolator could save cost. The 2500 Vrms isolation rating provides basic insulation for 240 VAC mains-referenced circuits and reinforced insulation for 125 VAC per IEC 60950-1. For 400 V motor-drive rails, you may need a higher-rated part. Common-mode transient immunity of 30 kV/µs ensures the data link stays intact when a motor drive or inverter switches at high dV/dt. In a noisy environment, this spec is what prevents bit errors. The integrated isolated power generates a regulated 5V or 3.3V (depending on the variant) on the bus side, so the transceiver can drive the RS485 bus without an external supply.
Package and layout considerations
The 32-BGA (15x11.25 mm) package requires a multi-layer PCB with at least four layers for proper signal and power routing. The BGA footprint has a 1.27 mm pitch, so standard via-in-pad or dogbone fanout works with most PCB fab processes. No special reflow profile beyond the standard lead-free SAC305 is needed. Place the part close to the RS485 connector to minimize stub length on the bus-side traces. The integrated DC/DC converter benefits from a 10 µF ceramic capacitor on the Vout pin per the datasheet recommendation.
Lifecycle and compliance
The part is ROHS3 compliant. If you need a 5V bus-side supply, the sibling LTM2881HY-5#PBF offers the same isolation and data rate with a 5V output from the integrated converter.