MT3540-F25 from Aerosemi, in a SOT-23-5. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	SW	power_out	Power switch output. Drain of the internal NMOS power switch (RDS(on) ≈ 0.5Ω, 1.5A current limit). Connects to the boost inductor and the anode of the Schottky rectifier; can swing between GND and 28V.
2	GND	power_in	Device ground and return for the internal power MOSFET. Tie to a solid ground plane close to the input/output capacitor grounds for best noise and thermal performance.
3	FB	input	Feedback input to the internal error amplifier. Regulates to VFB = 1.25V (MT3540-F25 variant). Drive with a resistor divider from VOUT: VOUT = 1.25V × (1 + R1/R2). Input bias current ≈ -10nA (typ).
4	EN	input	Regulator on/off control. Drive high (VIH ≥ 1.5V) to enable the converter; drive low (VIL ≤ 0.4V) to shut it down (IQ ≈ 0.1µA). Tie to VIN for always-on / automatic startup. Do not leave floating. Absolute max -0.3V to 6V.
5	VIN	power_in	Input supply pin, 2.5V to 5.5V operating range (absolute max 6V). Must be locally bypassed with a low-ESR ceramic capacitor (≥1µF, 10µF typical) placed close to the pin. UVLO ≈ 2.2V with 100mV hysteresis.

Key specifications

Parameter	Value
Manufacturer	Aerosemi
Package	SOT-23-5
Category	PMIC
Pins	5

Ordering variants

Same part, different packaging or reel option.

MT3540-F25

CAD (KiCad official)

Symbol: MT3540-F25
Footprint: Package_TO_SOT_SMD:SOT-23-5
3D model: SOT-23-5 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`mt3540-f25.step`	85 KB	You want the bare part, or you mark your own boards.
`mt3540-f25-etched.step`	1.8 MB	You want the part with `MT3540-F25` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 452 faces against 102 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Aerosemi datasheet (8 pp, sha256 883fdc668f7ca165, retrieved 2026-08-17, tier: lcsc)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF