LM331N from HGSEMI, 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	IOUT	output	Current output. Switched precision current source output (nominally i = 1.90V/RS, ~135 uA with RS=14 kOhm) that delivers a fixed charge Q = i*t into the load capacitor CL each timing cycle.
2	IREF	output	Reference current / bandgap reference pin. Held at 1.90 VDC by the internal current pump; an external resistor RS from pin 2 to ground sets the reference current i = 1.90V/RS (typ. 10 uA to 500 uA operating range).
3	FOUT	output	Frequency output. Open-collector logic output (VSAT ~0.15 V at 5 mA); requires an external pull-up (e.g. 10 kOhm to VLOGIC). Capable of driving up to 3 TTL loads or a high-voltage output up to 40V; short-circuit-proof against VCC.
4	GND	power_in	Device ground. All voltages are referenced to GND = 0V.
5	R/C	passive	Timing RC network pin. External Rt (to VS) and Ct (to GND) set the one-shot period t = 1.1RtCt. Internal timer comparator trips at 2/3 VCC (threshold 0.63-0.70 x VS), then an internal reset transistor discharges Ct (VSAT ~0.22 V at 5 mA).
6	THRESHOLD	input	Input comparator inverting input (threshold). Compared to the input at pin 7 by the input comparator. Bias current ~-80 nA typ; common-mode range -0.2V to VCC-2V.
7	VIN	input	Comparator input (non-inverting input of the input comparator). Applied signal voltage V1; when V1 > Vx at pin 6 the one-shot timer is triggered. Bias current ~-80 nA typ; common-mode range -0.2V to VCC-2V.
8	VS	power_in	Positive supply voltage (VS / VCC). Operating range +4V to +40V; absolute max 40V. Typical supply current 1.5-4.0 mA at VS=5V (LM331).

Key specifications

Parameter	Value
Manufacturer	HGSEMI
Package	DIP-8
Category	Data Acquisition
Pins	8

Ordering variants

Same part, different packaging or reel option.

LM331N
LM331AN
LM331M/TR
LM331AM/TR

CAD (KiCad official)

Symbol: LM331N
Footprint: Package_DIP:DIP-8_W7.62mm
3D model: DIP-8 (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: HGSEMI datasheet (21 pp, sha256 cbb85fee4a95c1f7, 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