The STMicroelectronics BAT54WFILMY is a Schottky barrier diode in the Q Automotive series, rated for a maximum DC reverse voltage of 40 V and an average rectified forward current of 300 mA. Its 5 ns reverse recovery time makes it suitable for fast-switching rectification, freewheeling, and polarity protection in automotive and industrial power rails where low forward voltage drop and minimal stored charge are required.
Junction temperature range and automotive qualification
The Q Automotive series designation indicates this device is qualified for automotive applications, supporting AEC-Q101 compliance (typical for ST's Q-series diodes). For a BOM that must survive thermal cycling and high ambient heat, this part keeps the margin on the rectifier stage.
Package and footprint — SOT-323
Housed in a SOT-323 (SC-70) surface-mount package, the BAT54WFILMY occupies minimal board area — roughly 2.0 mm × 1.25 mm footprint. The small outline suits dense layouts in ECU modules, sensor interfaces, and compact power supplies. Standard SOT-323 land pattern applies; no special thermal pad is needed for the 300 mA average current.
Reverse leakage and capacitance — signal-path considerations
Reverse leakage is specified at 1 µA maximum at 30 V reverse voltage, which is low enough for battery-powered circuits where quiescent draw matters. Junction capacitance is 10 pF at 1 V, 1 MHz — this keeps the diode transparent in high-speed switching nodes up to several MHz, though for RF or fast digital lines you should verify the RC time constant against your edge rate.
Forward voltage drop at rated current
Forward voltage is 900 mV maximum at 100 mA forward current. This is typical for a small-signal Schottky — the drop is higher than a 1 A-rated Schottky but acceptable for the 300 mA average current rating. For low-voltage rails (3.3 V or below), the 900 mV drop at 100 mA represents about 27% of the rail, so consider a lower-Vf Schottky if your design runs from a 1.8 V supply.
This is a current-production part available through independent distribution. For production BOMs, the active lifecycle means no forced redesign for obsolescence in the near term. The base product number BAT54 covers a family of single and dual Schottky diodes in various packages, so if you need a dual version or a different footprint, the family gives you options without requalifying the electrical characteristics.