UC3842BD1013TR 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 brought out for external loop compensation. Connect the feedback network (Zf) between this pin and VFB. Also serves as the PWM comparator control input via an internal 2R/R divider and 1.4 V level shift.
2	VFB	input	Inverting input of the internal error amplifier (non-inverting input tied to the 2.5 V reference). Normally connected to the switching supply output through a resistor divider to set the regulation point. Analog input rated -0.3 V to 5.5 V.
3	ISENSE	input	Current-sense input. A voltage proportional to inductor/switch current is applied here; when it reaches ~1.0 V the PWM latch terminates the output pulse for cycle-by-cycle current limiting. Analog input rated -0.3 V to 5.5 V.
4	RT/CT	passive	Oscillator timing node. Connect a resistor RT from VREF (pin 8) to this pin and a timing capacitor CT from this pin to GND to program the oscillator frequency and maximum output duty cycle. Operation to 500 kHz is possible.
5	GROUND	power_in	Combined control-circuitry and power (output-stage return) ground. All voltages in the datasheet are referenced to this pin; provide a single-point ground with timing/bypass capacitors returned here.
6	OUTPUT	output	Totem-pole gate-drive output for an external N-channel power MOSFET. Sources and sinks peak currents up to 1 A (±1 A absolute max). Output is held low during UVLO. Typical VOH ≈ 13.5 V at 200 mA source; VOL ≈ 1.6 V at 200 mA sink. Rise/fall times ~50 ns into 1 nF.
7	VCC	power_in	Positive supply for the control IC (labeled Vi/VCC). Absolute maximum 30 V from a low-impedance source (self-limiting at ~36 V zener clamp with Ii<30 mA). UC3842B start threshold ~16 V, min operating voltage after turn-on ~10 V (UVLO hysteresis). Start-up current <0.5 mA; operating supply current ~12 mA typ.
8	VREF	power_out	Trimmed 5 V reference output (5.00 V typ, ±2% at 25 °C). Sources up to 50 mA (short-circuit current ~-100 mA typ). Provides charging current for the timing capacitor CT through the timing resistor RT connected to pin 4.

Key specifications

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

Ordering variants

Same part, different packaging or reel option.

UC3842BD1013TR
UC3842BD1013TRBN
UC3842BD1013TRN

CAD (KiCad official)

Symbol: UC3842BD1013TR
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
`uc3842bd1013tr.step`	122 KB	You want the bare part, or you mark your own boards.
`uc3842bd1013tr-etched.step`	3.1 MB	You want the part with `UC3842BD1013TR` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 746 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