L78L18ACUTR from STMicroelectronics, in a SOT-89-3. 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	VOUT	power_out	Regulated +18 V output (±4% for 'AC' grade). Delivers up to 100 mA with adequate heat-sinking. A 0.1 µF ceramic capacitor to GND is recommended at the pin to improve transient response and stability.
2	GND	power_in	Common ground reference for input and output. The SOT-89 large center tab is also connected to GND and serves as the primary thermal path to the PCB copper (Rth(j-c) = 15 °C/W, Rth(j-a) ≈ 55 °C/W with 6 cm² copper).
3	VIN	power_in	Unregulated positive DC input. For an 18 V output the input voltage must remain within the 35 V absolute maximum (VO = 12-15 V rating in Table 1 extends to 40 V for VO = 18-24 V devices, so VIN(max) = 40 V for the 18 V option). Dropout voltage is typically 1.7 V. A 0.33 µF capacitor from VIN to GND is recommended if the regulator is far from the power-supply filter.

Key specifications

Parameter	Value
Manufacturer	STMicroelectronics
Package	SOT-89-3
Category	PMIC
Pins	3

Ordering variants

Same part, different packaging or reel option.

L78L18ACUTR
L78L18ACUTRZ
L78L18ACUTR-AP
L78L18ACUTRD
L78L18ACUTRD13TR

CAD (KiCad official)

Symbol: L78L18ACUTR
Footprint: Package_TO_SOT_SMD:SOT-89-3
3D model: SOT-89-3 (KiCad packages3D, STEP)

Provenance

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

Datasheet: STMicroelectronics datasheet (40 pp, sha256 8b73c521b7f1b36e, 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