The STD9NM40N is an STMicroelectronics N-channel power MOSFET built on the MDmesh™ II high-voltage trench-gate platform. This part is packaged in a DPAK (TO-252) surface-mount case, suited for automated assembly on power-supply and offline-converter boards.
NRND — plan a last-time buy or a design-in alternate
This is an official signal from ST that the part is in phase-out — it remains available for existing production but is not intended for new design starts. Buyers supporting active BOM lines should secure last-time-buy quantities or evaluate a pin-compatible replacement.
DPAK footprint and thermal management
The DPAK (TO-252) package occupies a standard surface-mount land pattern, with the tab as the drain connection and a thermal pad area that carries the bulk of the dissipation. A via-stitched copper pad under the tab is recommended to spread heat. The ±25 V maximum gate-source voltage is a standard limit; the drive voltage for achieving the rated on-resistance is 10 V, but the part can be driven with lower gate voltages if the increased Rds(on) is acceptable.