TX6121 from XDS, in a SOT-23-6. 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	DRV	output	External MOSFET gate driver output. Drives the gate of the external N-channel power MOS switch. Typical rise/fall time 50 ns into 500 pF load; minimum on-time 250 ns.
2	GND	power_in	Device ground reference for all internal circuitry and the CS sense resistor return.
3	DIM	input	Dimming input. Pulling below ~0.2 V shuts off the LED output; driving above 1.3 V gives 100% output current. Supports both PWM dimming and linear (analog) dimming with an analog range of 0.3-1.25 V. Must not be left floating; tie high if dimming is not used. For linear dimming, connect a small (>=10 nF) capacitor to GND.
4	VDD	power_in	Chip supply pin with internal VDD shunt (zener) regulator, typically clamped at 5.5 V (I_VDD < 10 mA). Fed from the input rail (3.6-100 V) through an external dropping resistor R1 = (VIN - VDD)/I_VDD. UVLO threshold 3.2 V (rising) with 0.5 V hysteresis; operating current 1.3 mA at 200 kHz.
5	TOFF	input	Off-time setting pin. Fixed switch off-time is set by a capacitor C1 to GND via T_OFF = 0.51 x 150 kOhm x (C1 + 8 pF) + T_D, where T_D = 61 ns. With no external capacitor, off-time defaults to ~650 ns (internal).
6	CS	input	Inductor peak current sense input. Compared against internal threshold VCS_TH (typ 255 mV, 245-265 mV) to terminate the MOSFET on-cycle. Connect to the top of the external current-sense resistor R2 between the MOSFET source and GND.

Key specifications

Parameter	Value
Manufacturer	XDS
Package	SOT-23-6
Category	LED-drv
Pins	6

CAD (KiCad official)

Symbol: TX6121
Footprint: Package_TO_SOT_SMD:SOT-23-6
3D model: SOT-23-6 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`tx6121.step`	97 KB	You want the bare part, or you mark your own boards.
`tx6121-etched.step`	1.2 MB	You want the part with `TX6121` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 298 faces against 117 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: XDS datasheet (7 pp, sha256 771392e4b805f3f6, 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