UC3843BD1R2G 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, made available for external loop compensation (typically an R-C network to the Voltage Feedback pin). Also serves as the PWM comparator control input internally.
2	Voltage Feedback	input	Inverting input of the Error Amplifier. Normally connected to the switching power supply output via a resistor divider; regulated against the internal 2.5 V reference tap.
3	Current Sense	input	Current sense input. A voltage proportional to inductor/switch current is applied here; the internal PWM uses this to terminate output switch conduction on a cycle-by-cycle basis. Threshold ~1.0 V.
4	RT/CT	passive	Oscillator timing pin. Connect timing resistor RT from Vref to this pin and timing capacitor CT from this pin to ground to program oscillator frequency and maximum duty cycle. Operation up to 500 kHz.
5	GND	power_in	Combined control circuitry and power ground return for the 8-pin package.
6	Output	output	Totem-pole gate-drive output. Directly drives the gate of an external power MOSFET, sourcing and sinking peak currents up to 1.0 A.
7	VCC	power_in	Positive supply for the control IC. UC3843B UVLO turn-on threshold 8.5 V typ, turn-off 7.6 V typ; absolute max 30 V. Internal Zener clamps at ~36 V (ICC = 25 mA).
8	Vref	power_out	Trimmed 5.0 V reference output (4.9-5.1 V). Supplies charging current for timing capacitor CT through resistor RT and can source external loads up to ~20 mA. Short-circuit protected (~85 mA).

Key specifications

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

Ordering variants

Same part, different packaging or reel option.

UC3843BD1R2G
UC3843BD1R2GD1G
UC3843BD1R2GNG
UC3843BD1R2GDG
UC3843BD1R2GDR2G

CAD (KiCad official)

Symbol: UC3843BD1R2G
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
`uc3843bd1r2g.step`	122 KB	You want the bare part, or you mark your own boards.
`uc3843bd1r2g-etched.step`	2.9 MB	You want the part with `UC3843BD1R2G` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 694 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 581ae31fbd1f3e07, 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