OC5021B from OCX, 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	Gate drive output for the external N-channel MOSFET switch. Typical drive voltage ~5.5V (clamped by internal VDD regulator). Rise/fall times ~50ns into 500pF; minimum on-time 250ns.
2	VSS	power_in	Device ground reference. Also the low side of the CS current sense; the trace from RCS to VSS and CS should be kept short and thick to minimize parasitic resistance.
3	DIM	input	Dimming input, supports both PWM and linear dimming. DIM tied to GND shuts off the LED output; DIM > 3.1V gives 100% output current; linear dimming range is 1.1V-3.1V (shutdown threshold ~0.9V). Must not be left floating; tie high if unused. For linear dimming, add a small capacitor (>=10nF) to ground.
4	VDD	power_in	Chip supply pin, fed from VIN through an external series resistor RVDD. Internally clamped to ~5.5V by an integrated shunt regulator (max clamp current 10mA). UVLO ~2.6V rising with ~0.4V hysteresis; typical operating current 1.3mA at 200kHz.
5	TOFF	input	Off-time setting pin. External capacitor COFF to ground sets fixed off-time per TOFF = 0.51 * 150k * (COFF + 8pF) + 61ns. With no external cap, internal off-time defaults to 650ns.
6	CS	input	Inductor peak current sense input, connects to the top of the external current-sense resistor RCS. Peak-current comparator threshold VCS_TH = 245/255/265 mV (min/typ/max). When VCS reaches threshold, DRV turns off the external MOSFET.

Key specifications

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

CAD (KiCad official)

Symbol: OC5021B
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
`oc5021b.step`	97 KB	You want the bare part, or you mark your own boards.
`oc5021b-etched.step`	1.6 MB	You want the part with `OC5021B` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 393 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: OCX datasheet (7 pp, sha256 2c27bff9309b1edf, 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