UC3843M from HGSEMI, in a SOP-8. 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	COMP	output	Error amplifier output. Used for loop compensation; an external RC network from COMP to VFB (pin 2) sets the compensation of the voltage feedback loop.
2	VFB	input	Voltage feedback input - inverting input of the internal error amplifier. Typically connected to the switching power supply output through a resistor divider; internally compared against the 2.5 V reference.
3	ISENSE	input	Current sense input. A voltage proportional to the switching inductor current is applied here (typically from a sense resistor Rs). The PWM latch resets and terminates the output pulse when this input exceeds ~1.0 V.
4	RT/CT	passive	Oscillator timing pin. Connect RT from VREF (pin 8) to this pin, and CT from this pin to GND to set the oscillator frequency and maximum duty cycle. Maximum operating frequency up to 500 kHz.
5	GND	power_in	Device ground. Common return for control-circuit bias current and reference for all internal voltages.
6	OUTPUT	output	Totem-pole gate-drive output. Directly drives the gate of an external power MOSFET; capable of sourcing/sinking up to ±1 A peak. Held low when Vcc is below the UVLO threshold.
7	VCC	power_in	Positive supply input for the IC. Operating range approximately 8.4 V (UVLO turn-on) to 30 V (absolute max); startup current <0.5 mA, operating supply current typ. 12 mA. Internal 34 V zener clamp on this pin.
8	VREF	power_out	5.0 V precision reference output (4.90-5.10 V, 1 mA load). Provides charging current through RT to the timing capacitor CT and can supply external loads up to ~20 mA; short-circuit current typ. -100 mA.

Key specifications

Parameter	Value
Manufacturer	HGSEMI
Package	SOP-8
Category	PMIC
Pins	8

Ordering variants

Same part, different packaging or reel option.

UC3843MM/TR
UC3843MN

CAD (KiCad official)

Symbol: UC3843M
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOP-8 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`uc3843m.step`	122 KB	You want the bare part, or you mark your own boards.
`uc3843m-etched.step`	2.0 MB	You want the part with `UC3843M` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 469 faces against 147 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: HGSEMI datasheet (10 pp, sha256 549a60aef8d59c3f, 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