SA555DR from Texas Instruments, in a SOIC-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	GND	power_in	Ground reference (0 V) for the device.
2	TRIG	input	Trigger input. The output pulse begins when a negative-going pulse on TRIG crosses below 1/3 VCC, setting the internal flip-flop and driving OUT high.
3	OUT	output	Timer output. Drives high (near VCC) during the timing interval and low (near GND) otherwise. Capable of sourcing/sinking up to ~200 mA.
4	RESET	input	Active-low reset. When held below ~0.7 V, the timing cycle is interrupted and OUT is forced low. Tie to VCC when unused.
5	CONT	input	Control voltage. Provides access to the internal 2/3 VCC threshold reference. Typically bypassed to GND with a 10 nF capacitor for noise immunity; can be driven to modulate the timing thresholds.
6	THRES	input	Threshold input. Resets the internal flip-flop (ending the output pulse) when the voltage on THRES rises above 2/3 VCC.
7	DISCH	output	Discharge. Open-collector output tied to the timing capacitor; provides a low-impedance path to GND to discharge the external timing capacitor between cycles.
8	VCC	power_in	Positive supply voltage. Operating range 4.5 V to 16 V.

Key specifications

Parameter	Value
Manufacturer	Texas Instruments
Package	SOIC-8
Category	RTC
Pins	8

Ordering variants

Same part, different packaging or reel option.

SA555DR
SA555DRD
SA555DRP

CAD (KiCad official)

Symbol: SA555DR
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`sa555dr.step`	122 KB	You want the bare part, or you mark your own boards.
`sa555dr-etched.step`	1.8 MB	You want the part with `SA555DR` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 439 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: Texas Instruments datasheet (39 pp, sha256 c6f5275b8c31eb1d, 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