The classic 555 precision timing circuit, in a SOIC-8 package. An external RC network sets accurate time delays (monostable) or oscillation (astable); the output sinks or sources up to 200 mA and is TTL-compatible at 5 V. It runs from 4.5 to 16 V. The default building block for delays, blinkers, PWM, tone generation, and simple clocks.

Pinout

Pin	Name	Type	Function
1	GND	power_in	Ground reference (0 V). All voltages in the device are referenced to this pin.
2	TRIG	input	Trigger input. Starts the timing cycle: when TRIG falls below approximately 1/3 VCC (< 1/2 CONT), the internal flip-flop is set, the output goes high, and the discharge switch opens.
3	OUT	output	High-current timer output signal. Can sink or source up to 200 mA; TTL-compatible at VCC = 5 V. High level is approximately VCC - 1.7 V, low level is near GND.
4	RESET	input	Active-low reset input. When driven below approximately 0.7 V, the flip-flop is reset and the output is forced low regardless of TRIG/THRES. Tie to VCC when reset is not used.
5	CONT	bidirectional	Control voltage pin. Directly sets the upper comparator threshold (nominally 2/3 VCC) and indirectly the lower threshold (1/2 CONT). Bypass to GND with a 0.01 uF capacitor when not driven externally.
6	THRES	input	Threshold input. End of timing input: when THRES exceeds CONT (nominally 2/3 VCC), the flip-flop is reset, the output goes low and the discharge switch closes.
7	DISCH	output	Discharge. Open-collector output used to discharge the external timing capacitor. Sinks current to GND whenever the internal flip-flop is reset (output low).
8	VCC	power_in	Positive supply voltage. Recommended operating range 4.5 V to 16 V (SE555: up to 18 V). Bypass with a low-ESR ceramic capacitor to GND.

Key specifications

Parameter	Value
Type	Precision timer (555)
Modes	Monostable, astable
Supply voltage	4.5-16 V
Output current	±200 mA (TTL-compatible)
Timing	External RC network
Package	SOIC-8
Body (L×W×H)	4.9 × 3.9 × 1.75 mm

Ordering variants

Same part, different packaging or reel option.

NE555D (SOIC-8, tube)
NE555DR (SOIC-8, tape & reel)

CAD (KiCad official)

Symbol: Timer:NE555D
Footprint: Package_SO:SOIC-8_3.9x4.9mm_P1.27mm
3D model: SOIC-8 (KiCad packages3D)

Provenance

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

Datasheet: Texas Instruments datasheet (39 pp, sha256 dae2be1a919b0cfe, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude) — every pin and dimension is cited to a datasheet page; refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF