UC3845BD1R2G from onsemi, in a SOIC-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	Compensation	output	Error amplifier output / compensation node. External RC network to Voltage Feedback (pin 2) sets the closed-loop gain and frequency response of the error amplifier used for output regulation.
2	Voltage Feedback	input	Inverting input of the on-chip error amplifier. Normally connected to the switching power supply output through a resistor divider; the non-inverting input is internally tied to the 2.5 V reference (VFB regulation set point ~2.5 V).
3	Current Sense	input	Non-inverting input of the current-sense comparator. Monitors the MOSFET source current across a sense resistor; the internal PWM latch is reset (output terminates) when this pin reaches the threshold set by the error amp output (nominal max threshold 1.0 V).
4	RT/CT	passive	Oscillator timing pin. External resistor RT to Vref and timing capacitor CT to GND set the oscillator frequency (fOSC ≈ 1.72 / (RT·CT) for RT > 5 kΩ). Output switching frequency equals oscillator frequency.
5	GND	power_in	Device ground and current return for control circuitry and totem-pole output stage. In the SOIC-8/PDIP-8 package the signal and power grounds share this pin (the SOIC-14 D-suffix splits them).
6	Output	output	High-current totem-pole gate-drive output for the external power MOSFET. Capable of ±1 A peak source/sink; typical VOH ≈ 13.5 V and VOL ≈ 0.1 V at 20 mA. Rise/fall times ~50 ns into 1 nF.
7	VCC	power_in	Positive supply for the control IC and output driver. UVLO thresholds for the UC3845B are 8.5 V (on) / 7.6 V (off). Absolute max 36 V (internally zener-clamped); typical startup current 0.3 mA, operating current ~12 mA.
8	Vref	power_out	Buffered 5.0 V ±1% precision reference output (4.95-5.05 V at 25 °C, 1 mA). Sources up to ~50 mA to bias external circuitry and to feed the oscillator timing resistor RT. Short-circuit protected (~85 mA typ).

Key specifications

Parameter	Value
Manufacturer	onsemi
Package	SOIC-8
Category	PMIC
Pins	8

Ordering variants

Same part, different packaging or reel option.

UC3845BD1R2G
UC3845BD1R2GD1G
UC3845BD1R2GN
UC3845BD1R2GNG
UC3845BD1R2GD
UC3845BD1R2GDG
UC3845BD1R2GDR2G

CAD (KiCad official)

Symbol: UC3845BD1R2G
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`uc3845bd1r2g.step`	122 KB	You want the bare part, or you mark your own boards.
`uc3845bd1r2g-etched.step`	2.8 MB	You want the part with `UC3845BD1R2G` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 680 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: onsemi datasheet (22 pp, sha256 811d8a44f6a2a239, retrieved 2026-08-17, tier: manufacturer)
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