UC3845B from UMW, 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 pin, used for external loop compensation. Typical high output voltage 5-6 V, low output 0.8-1.1 V (with 15 kΩ load).
2	VFB	input	Inverting input of the Error Amplifier. Normally connected to the switching power supply output through a resistor divider; internal reference at 2.5 V (typ). Input bias current -0.1 µA typ.
3	ISENSE	input	Current sense input. A voltage proportional to the inductor current (up to ~1 V max) is applied here; the PWM comparator uses this to terminate output switch conduction each cycle. Input voltage range -0.3 to 5.5 V max.
4	RT/CT	passive	Oscillator timing pin. Oscillator frequency and maximum output duty cycle are set by connecting a timing resistor RT from VREF to this pin and a timing capacitor CT from this pin to ground. Operating frequency up to 500 kHz.
5	GND	power_in	Combined control circuitry and power ground return for the IC.
6	OUT	output	Totem-pole gate drive output for an external power MOSFET. Sources/sinks peak currents up to 1 A. VOH ≈ 13-13.5 V, VOL ≈ 0.08-1.4 V depending on load; rise/fall time ~35-45 ns into 1 nF.
7	VCC	power_in	Positive supply for the IC. UVLO start threshold 8.4 V typ (7.8-9 V), min operating 7.6 V typ (7-8.2 V) after turn-on. Absolute max 30 V; zener clamp ≈ 30-38 V at 25 mA. Operating supply current 13 mA typ; start-up current 0.5 mA typ.
8	VREF	power_out	Internal 5 V reference output (4.9-5.1 V), used to charge timing capacitor CT through timing resistor RT and to bias external circuitry. Short-circuit current typically -100 mA (limited to -180 mA max). Load current 1-20 mA.

Key specifications

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

Ordering variants

Same part, different packaging or reel option.

UC3845B

CAD (KiCad official)

Symbol: UC3845B
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
`uc3845b.step`	122 KB	You want the bare part, or you mark your own boards.
`uc3845b-etched.step`	2.0 MB	You want the part with `UC3845B` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 481 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: UMW datasheet (13 pp, sha256 562bc6cb07a3fb91, 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