The Original NE555 General Purpose Single Timer is an industry-standard precision timing integrated circuit manufactured by Texas Instruments / STMicroelectronics. Encapsulated in a standard DIP-8 through-hole package, it is capable of generating highly accurate, stable time delays and oscillation across two primary operating modes: Monostable (one-shot pulse generator) and Astable (free-running square-wave oscillator). Operating across a wide supply voltage range of 4.5V to 16V DC, the NE555 provides timing intervals ranging from microseconds to hours, set precisely by external resistors and capacitors. It features a high-current totem-pole output capable of sourcing or sinking up to 200mA, allowing direct driving of relays, LEDs, small DC motors, and logic circuitry without external driver transistors. It is widely used in pulse generators, delay timers, PWM motor speed controllers, tone alarms, and digital sequential logic circuits.

Specifications

• Part Number / Model: NE555 / NE555P (Commercial Temperature Range)
• Device Function: Precision Timer / Pulse Generator / Astable Oscillator
• Package Type: DIP-8 (Dual In-Line 8-Pin Through-Hole, Plastic)
• Supply Voltage Range (Vcc): 4.5V to 16V DC (Absolute Max: 18V)
• Supply Current (Icc): Typ. 3.0mA (at Vcc = 5V, Low State) / Typ. 10mA to 15mA (at Vcc = 15V)
• Output Current Capability (Pin 3): Sink / Source up to 200mA (Max)
• Output Voltage Drop (High State): Min. 12.5V (at Vcc = 15V, Isource = 200mA) / Typ. 13.3V (Isource = 100mA)
• Output Voltage Drop (Low State): Typ. 0.1V (at Vcc = 5V, Isink = 8mA) / Max. 2.5V (at Vcc = 15V, Isink = 200mA)
• Threshold Voltage Level (Pin 6): Typ. 2/3 Vcc (at Vcc = 5V to 15V)
• Trigger Voltage Level (Pin 2): Typ. 1/3 Vcc (at Vcc = 5V to 15V)
• Reset Voltage Threshold (Pin 4): Typ. 0.7V / Max. 1.0V (Active-Low)
• Timing Error (Monostable Initial Accuracy): Typ. 1.0% (at Ra = 1kΩ to 100kΩ, C = 0.1µF)
• Timing Drift with Temperature: Typ. 50 ppm/°C
• Timing Drift with Supply Voltage: Typ. 0.1 %/V
• Maximum Oscillation Frequency: Typ. 100 kHz to 500 kHz (depending on circuit configuration)
• Power Dissipation (Pd): 600mW to 1000mW (at Ta = 25°C)
• Operating Ambient Temperature (Ta): 0°C to +70°C
• Storage Temperature Range (Tstg): -65°C to +150°C
• Pinout Configuration:
  • Pin 1: Ground (GND)
  • Pin 2: Trigger (TRIG) - Initiates timing cycle when voltage drops below 1/3 Vcc
  • Pin 3: Output (OUT) - High-current totem-pole output
  • Pin 4: Reset (RESET) - Active-Low master reset
  • Pin 5: Control Voltage (CONT) - Accesses internal 2/3 Vcc divider tap for FM modulation or bypass
  • Pin 6: Threshold (THRES) - Terminates timing cycle when voltage rises above 2/3 Vcc
  • Pin 7: Discharge (DISCH) - Open-collector transistor to discharge timing capacitor
  • Pin 8: Supply Voltage (VCC / V+)

Features

• Dual Operational Modes: Seamlessly configured as a Monostable multivibrator (one-shot timer) or Astable multivibrator (free-running square wave generator) with minimal external RC components.
• High-Current 200mA Output: Direct-drive totem-pole stage allows sinking or sourcing up to 200mA, driving loads like relays, buzzers, and power MOSFET gates directly.
• TTL & CMOS Compatible: Fully compatible with standard 5V TTL and wide-range CMOS logic families across its 4.5V to 15V operating range.
• Adjustable Duty Cycle: In Astable mode, adding a steering diode across the timing resistor allows flexible pulse-width modulation (PWM) from <1>99% duty cycle.
• Independent Master Reset: Pin 4 (Active-Low) overrides all other inputs, instantly resetting the output to LOW state regardless of trigger or threshold status.
• Direct Breadboard Compatibility: Standard 0.1-inch (2.54mm) pin pitch DIP-8 footprint makes it ideal for educational labs, DIY electronics prototyping, and through-hole production boards.

Common Applications

• Precision Time Delay Relays: Power-on delay timers, staircase light controllers, and timed interval switches.
• Pulse-Width Modulation (PWM) Drivers: DC motor speed controllers, LED dimmers, and power supply switching regulators.
• Astable Square-Wave Oscillators: Clock generators for digital ICs, audio tone sirens, electronic metronomes, and flasher circuits.
• Missing-Pulse & Frequency Detectors: Monitoring continuous pulse streams to trigger alarms when a tachometer or heartbeat signal ceases.
• Sequential & Industrial Timing Controls: Multi-stage cascade timing logic, automated sensor debounce buffers, and toy electronics.

Usage Tips

• Bypass Pin 5 with a Ceramic Capacitor: Always connect a 10nF (0.01µF) or 100nF ceramic capacitor between Pin 5 (Control Voltage) and Pin 1 (GND) to filter high-frequency noise from shifting internal 2/3 Vcc and 1/3 Vcc threshold levels.
• Tie Unused Reset Pin to VCC: The Reset input (Pin 4) is active-LOW; never leave it floating. If not actively used for resetting, hardwire Pin 4 directly to Pin 8 (VCC) to prevent stray noise from resetting the timer.
• Add Robust Power Rail Decoupling: The internal totem-pole output draws a brief "shoot-through" current spike (up to 300mA) during output state transitions. Place a 10µF to 100µF electrolytic capacitor in parallel with a 100nF ceramic capacitor directly across Pin 8 (VCC) and Pin 1 (GND) to prevent power supply dips and false triggering.
• Timing Formula Reference:
  • Monostable Mode: Pulse duration T = 1.1 × R × C (in seconds).
  • Astable Mode: Charge time t1 = 0.693 × (R1 + R2) × C; Discharge time t2 = 0.693 × R2 × C; Frequency f = 1.44 / [(R1 + 2×R2) × C].
• Inductive Load Protection: When driving relay coils or solenoid valves from Pin 3 (OUT), wire a flyback diode (such as a 1N4007 or 1N4148) in reverse parallel across the coil to protect the internal output transistors from inductive kickback voltages.

Datasheet