What this HITFET low-side switch does
The Infineon BTS3134NNT is a single-channel, low-side N-channel power switch from the HITFET® family. It switches a grounded load on and off with a logic-level input — no external gate drive or Vcc supply required. The 35 mOhm typical Rds(on) keeps conduction losses low for loads up to 3 A continuous. Built-in fault protection covers current limiting (fixed threshold), over-temperature shutdown, and over-voltage clamping. That means a single device handles the switching and the protection, reducing BOM count in automotive and industrial low-side drive applications.
At 3 A load current, the 35 mOhm typical on-resistance produces about 315 mW of conduction loss (I²R). In the PG-SOT223-4 package with the large copper pad on the drain tab, that heat spreads into the board plane.
42 V load rating — 12 V automotive is comfortable
The 42 V maximum load voltage covers 12 V nominal automotive systems with headroom for load-dump transients that can spike above 30 V. The over-voltage clamp inside the switch absorbs those surges without external TVS diodes in many cases. For 24 V truck or industrial bus applications, the 42 V ceiling still provides margin.
Infineon lists the BTS3134NNT as obsolete. For existing designs that already qualify this switch, the only supply channel is the independent distribution market — new-old-stock or surplus inventory sourced per RFQ. The part is not in current factory production, so any BOM line using it should plan for a one-time buy or a qualification of a pin-compatible alternative.