LGS63040B5 from Legend Si, 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	output	Internal power switch node (drain of the 350mΩ low-side NMOS). Externally connected to the power inductor and Schottky freewheeling diode. High dv/dt node - keep copper area small to limit EMI.
2	GND	power_in	Device ground reference. Tie to a large ground pour for thermal and return-current path.
3	EN	input	Enable / dimming input. Digital high (>0.5V) enables the regulator; low (<0.4V) shuts it down. On LGS63040 accepts an analog voltage 0.6V-1.2V for analog dimming of LED current; on LGS63042 accepts a 100Hz-100kHz PWM square wave for PWM dimming. Internal 800kΩ pull-down; do not leave floating. Absolute max 6V.
4	CSN	input	LED current sense input. Connect to the LED-side node of the external sampling resistor R_Sence. Output current is set by I_OUT = (V_OUT(VIN) − V_CSN) / R_Sence, with typical V_OUT−V_CSN = 0.2V (0.195V-0.205V). High-impedance node - route short and away from SW.
5	VIN/OUT	power_in	Combined input supply pin and output-voltage sense point. Also the VIN-side terminal of the external LED current sampling resistor R_Sence. Serves as input-voltage detection in buck mode and as output-voltage connection in boost / buck-boost mode. Operating range 3.0V-60V (abs max 60V). Bypass with 4.7µF/100V X7R or X5R ceramic near the pin.

Key specifications

Parameter	Value
Manufacturer	Legend Si
Package	SOT-23-5
Category	LED-drv
Pins	5

Ordering variants

Same part, different packaging or reel option.

LGS63040B5
LGS63040B5EP

CAD (KiCad official)

Symbol: LGS63040B5
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
`lgs63040b5.step`	85 KB	You want the bare part, or you mark your own boards.
`lgs63040b5-etched.step`	2.4 MB	You want the part with `LGS63040B5` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 566 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: Legend Si datasheet (22 pp, sha256 13f24f98441db88d, 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