UC3843BD1013TR from STMicroelectronics, in a SO-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, made available for external loop compensation (typically an R-C network between COMP and VFB). Also serves as the input to the PWM comparator via an internal 2R:R divider and 1 V offset.
2	VFB	input	Inverting input of the internal Error Amplifier (non-inverting input tied to internal 2.50 V reference). Normally connected to the switching power supply output through a resistor divider for voltage-mode feedback. Input bias current typ -0.1 uA.
3	ISENSE	input	Current sense input. A voltage proportional to the switch/inductor current (typically from a source-side sense resistor) is applied here; the internal PWM current-sense comparator terminates the output switch conduction when this pin reaches ~1 V (max input signal 0.9-1.1 V, gain 3 V/V).
4	RT/CT	passive	Oscillator timing pin. Connect timing resistor RT from VREF (pin 8) 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	GROUND	power_in	Combined control-circuitry and power ground return. All bypass, timing capacitors and current-sense components must be referenced to this pin via a single-point ground.
6	OUTPUT	output	Totem-pole gate driver output for directly driving the gate of an external N-channel power MOSFET. Sources/sinks up to ±1 A peak; rise/fall time typ 50 ns into 1 nF; low in the off-state.
7	Vi	power_in	Positive supply (VCC) of the control IC. Absolute maximum 30 V (self-limiting via internal 36 V zener at Ii<30 mA). UC3843B UVLO start threshold typ 8.5 V, minimum operating voltage after turn-on typ 7.6 V; operating supply current typ 12 mA.
8	VREF	power_out	Trimmed 5.00 V reference output (5 V ±2%, 50 mA capability). Supplies charging current to the timing capacitor CT via timing resistor RT and can be used to bias external circuitry. Short-circuit current typ -100 mA.

Key specifications

Parameter	Value
Manufacturer	STMicroelectronics
Package	SO-8
Category	PMIC
Pins	8

Ordering variants

Same part, different packaging or reel option.

UC3843BD1013TR
UC3843BD1013TRN
UC3843BD1013TRBN

CAD (KiCad official)

Symbol: UC3843BD1013TR
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SO-8 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`uc3843bd1013tr.step`	122 KB	You want the bare part, or you mark your own boards.
`uc3843bd1013tr-etched.step`	3.2 MB	You want the part with `UC3843BD1013TR` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 762 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: STMicroelectronics datasheet (15 pp, sha256 fedfd7362400f8b3, 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