QX9920 from QX Micro Devices, in a SOT-23-6L. 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	Gate drive output for the external N-channel power MOSFET. Provides the gate switching signal generated by the internal RS latch / off-time logic. Maximum pin current 100mA; leave floating when no external MOSFET is used.
2	VSS	power_in	Device ground / power return. Connects to the negative rail of the supply.
3	EN	input	Chip enable input, active high. Logic-high threshold 0.4*VOUT, logic-low ≤0.3V, input current 0.1µA at logic high. A PWM signal on EN dims the LED brightness.
4	VDD	power_in	Internal circuit supply pin. Operating range 2.5V to 6V (absolute range noted as 2V-6.5V in pin table). Typically fed from VIN through a series resistor with a 2.5V-5.5V zener clamp when VIN exceeds this range.
5	TOFF	input	External MOSFET off-time setting pin. Off-time set by an R (ROFF) and C (COFF) network to VDD/GND per TOFF = 0.51 * (100kΩ·ROFF / (ROFF+100kΩ)) * (COFF + 12pF). If left unconnected, internal off-time defaults to 612ns.
6	CS	input	Current-sense feedback input. Connect to the top of the source-sense resistor Rcs on the external MOSFET source. Internal reference is 250mV (240-260mV), so LED current I_LED = 250mV / Rcs.

Key specifications

Parameter	Value
Manufacturer	QX Micro Devices
Package	SOT-23-6L
Category	LED-drv
Pins	6

CAD (KiCad official)

Symbol: QX9920
Footprint: Package_TO_SOT_SMD:SOT-23-6
3D model: SOT-23-6L (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`qx9920.step`	97 KB	You want the bare part, or you mark your own boards.
`qx9920-etched.step`	1.6 MB	You want the part with `QX9920` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 382 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: QX Micro Devices datasheet (7 pp, sha256 48a3c3d1a329b82e, retrieved 2026-08-17, tier: lcsc)
Datasheet language: Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
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