What this Schottky diode brings to the board
The STMicroelectronics BAT54FILM is a 40 V, 300 mA Schottky barrier diode in the standard SOT-23-3 surface-mount package. The 10 pF junction capacitance at 1 V keeps signal distortion low in RF and fast-logic applications.
Ratings that define the fit
The 40 V maximum reverse voltage sets the rail ceiling for reverse-polarity blocking and low-side clamping. The 300 mA average rectified current covers typical signal-level loads and auxiliary supply rails; stay within this continuous limit for reliable operation. Forward voltage drops to 900 mV at 100 mA, which is typical for a Schottky in this current class and influences thermal dissipation in tight layouts. Reverse leakage is specified at 1 µA at 30 V, a figure that rises with junction temperature — factor in derating if the board runs near the 150 °C junction maximum. The 5 ns reverse recovery time is the headline switching spec: it allows the diode to turn off fast enough for 100 kHz+ rectifiers and snubber networks without excessive ringing.
Where it goes and what it handles
This diode is a standard building block for low-power DC-DC converter freewheeling paths, reverse-polarity protection on input lines up to 40 V, and signal clamping in I/O protection networks.