SN74LS21DR from Texas Instruments, in a SOIC-14. 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	1A	input	Gate 1 input A. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V. Input current IIH = 20 uA max at 2.7 V; IIL = -0.4 mA max at 0.4 V.
2	1B	input	Gate 1 input B. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V.
3	NC	unconnected	No internal connection. Leave floating or tie to a convenient net.
4	1C	input	Gate 1 input C. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V.
5	1D	input	Gate 1 input D. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V.
6	1Y	output	Gate 1 output. Y = 1A AND 1B AND 1C AND 1D (positive logic). LSTTL totem-pole output; VOH >= 2.7 V at IOH = -0.4 mA; VOL <= 0.5 V at IOL = 8 mA.
7	GND	power_in	Device ground reference (0 V).
8	2Y	output	Gate 2 output. Y = 2A AND 2B AND 2C AND 2D (positive logic). LSTTL totem-pole output; VOH >= 2.7 V at IOH = -0.4 mA; VOL <= 0.5 V at IOL = 8 mA.
9	2A	input	Gate 2 input A. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V.
10	2B	input	Gate 2 input B. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V.
11	NC	unconnected	No internal connection. Leave floating or tie to a convenient net.
12	2C	input	Gate 2 input C. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V.
13	2D	input	Gate 2 input D. LSTTL logic input; VIH >= 2 V, VIL <= 0.8 V.
14	VCC	power_in	Positive supply. Recommended 4.75-5.25 V (SN74LS21), absolute maximum 7 V. Typical ICCH = 1.2 mA, ICCL = 2.2 mA.

Key specifications

Parameter	Value
Manufacturer	Texas Instruments
Package	SOIC-14
Category	Logic
Pins	14

Ordering variants

Same part, different packaging or reel option.

SN74LS21DRD
SN74LS21DR
SN74LS21DRN
SN74LS21DRNE4
SN74LS21DRNSR
SN74LS21DRJ
SN74LS21DRW
SN74LS21DRFK

CAD (KiCad official)

Symbol: SN74LS21DR
Footprint: Package_SO:SOIC-14_3.9x8.7mm_P1.27mm
3D model: SOIC-14 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`sn74ls21dr.step`	195 KB	You want the bare part, or you mark your own boards.
`sn74ls21dr-etched.step`	2.2 MB	You want the part with `SN74LS21DR` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 566 faces against 237 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: Texas Instruments datasheet (20 pp, sha256 de3373b5914eb45e, 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