The STMicroelectronics BAT54WFILM is a Schottky barrier diode rated for 300 mA average rectified current and a 40 V DC reverse voltage. It switches fast — 5 ns reverse recovery time — and drops 900 mV at 100 mA forward current. Reverse leakage is 1 µA at 30 V. The device comes in an SOT-323 surface-mount package, which is the SC-70 variant footprint. This is a small-signal Schottky suited for low-voltage rectification, freewheeling, and clamping in compact designs where board area is tight.
The BAT54WFILM is marked obsolete by STMicroelectronics. The last-time-buy window has closed. Any stock still in the channel is residual inventory — once it is gone, it is gone.
5 ns reverse recovery — why it matters
A 5 ns trr is fast for a 300 mA Schottky. In a high-frequency switching supply or a snubber clamp, that speed means the diode stops conducting almost immediately when the voltage reverses, reducing switching losses and ringing. The 10 pF junction capacitance at 1 V also helps keep the switching node clean. If your circuit runs above a few hundred kilohertz, this diode will not be the bottleneck.
Temperature range and junction limits
That is the full operating junction temperature range — not just storage. The device can handle the thermal cycling of outdoor or industrial environments, but the 150°C ceiling means you need to derate the forward current if the ambient is high and the board has poor heat sinking. In a 85°C ambient, the 300 mA rating is still usable with reasonable copper area on the pads.