UC3843BN from STMicroelectronics, in a DIP-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, made available for external loop compensation. Typically connected via an RC network back to VFB (pin 2) to shape the control-loop response. Output high ~6.2V, output low ~0.8V-1.1V.
2	VFB	input	Inverting input of the internal Error Amplifier. Normally connected to the switching power supply output via a resistor divider for regulation feedback. Non-inverting input is internally tied to the 2.5V reference; input bias current typ -0.1uA.
3	ISENSE	input	Current sense input. A voltage proportional to the inductor/switch current (typically developed across a sense resistor) is applied here. The PWM comparator uses this to terminate the output switch conduction on a cycle-by-cycle basis. Maximum input signal ~1V.
4	RT/CT	passive	Oscillator timing pin. Programs the switching frequency and maximum output duty cycle by connecting timing resistor RT from this pin to VREF (pin 8) and timing capacitor CT from this pin to GROUND. Operation up to 500kHz is possible.
5	GROUND	power_in	Combined control-circuit and power ground return. All voltages in the datasheet are referenced to this pin. Single-point grounding is recommended due to high peak output currents.
6	OUTPUT	output	High-current totem-pole gate drive output for directly driving the gate of an external power N-channel MOSFET. Peak source/sink currents up to +/-1A. Output high ~13.5V @ 20mA source; output low ~0.1V @ 20mA sink. Rise/fall times ~50ns typ into 1nF.
7	Vi	power_in	Positive supply (VCC) of the control IC. Absolute maximum supply voltage 30V (low-impedance source); the pin is self-limiting from a high-impedance source (internal Zener ~36V @ 25mA). UC3843B UVLO turn-on threshold ~8.5V, turn-off ~7.9V. Operating supply current typ 12mA.
8	VREF	power_out	Trimmed 5.0V reference output (5V, 50mA). Provides charging current for timing capacitor CT through timing resistor RT, and can be used as a reference/supply for external circuitry. Short-circuit current typ -100mA.

Key specifications

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

Ordering variants

Same part, different packaging or reel option.

UC3843BNN
UC3843BND1

CAD (KiCad official)

Symbol: UC3843BN
Footprint: Package_DIP:DIP-8_W7.62mm
3D model: DIP-8 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`uc3843bn.step`	271 KB	You want the bare part, or you mark your own boards.
`uc3843bn-etched.step`	2.2 MB	You want the part with `UC3843BN` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 516 faces against 148 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 62066370bcc6f048, 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