Transformer driver for isolated RS485 power
The MAX253CSA+ from Maxim Integrated is a dedicated transformer driver IC designed to generate an isolated power supply for RS485 transceivers and similar isolated interfaces. It integrates an oscillator and power stage that drives a centre-tapped transformer from a 3.3 V or 5 V rail, producing a clean, isolated secondary voltage with minimal external components. The part draws only 450 µA supply current, making it suitable for loop-powered or low-power isolated channels where every milliamp counts. It comes in an 8-SOIC surface-mount package and is rated for the commercial temperature range of 0°C to 70°C, so it fits indoor equipment, office peripherals, and telecom line cards — not under-hood or outdoor enclosures without climate control.
Package and rework — 8-SOIC is bench-friendly
The 8-SOIC package (0.154" body width, 3.90 mm) is a standard footprint that hot-air rework handles cleanly. The leads are gull-wing, so visual inspection of solder joints is straightforward after reflow. Tube shipment means the parts arrive aligned and undamaged; no tape-and-reel feeding issues for small-batch assembly.
Supply voltage — runs on 3.3 V or 5 V without a regulator
The MAX253CSA+ accepts either a 3.3 V or 5 V supply rail directly, with no external LDO needed. This simplifies BOM planning for mixed-voltage boards: if the isolated side runs on 3.3 V logic, the same rail powers the driver. The 450 µA quiescent current is the total draw from that rail when the transformer is unloaded; actual input current rises with the secondary load, but the no-load floor stays low enough for always-on isolated channels.
Lifecycle and sourcing — active, no LTB risk
The MAX253CSA+ carries an active lifecycle status per the manufacturer, with ROHS3 compliance. There is no last-time-buy notice or NRND flag.