LM555 Datasheet PDF – Single Timer – Fairchild

The LM555 is widely used in various applications, such as pulse generation, timing circuits, frequency generation, delay circuits, and sequential timing. It finds applications in areas such as electronic instrumentation, control systems, robotics, and hobbyist projects.

Part Number: LM555

Function : Single Timer

Package: 8-DIP, 8-SOIC

Manufactuers : Fairchild




This LM555 Timer is a highly stable controller capable of producing accurate timing pulses. With a monostable operation, the delay is controlled by one external resistor and one capacitor.

With astable operation, the frequency and duty cycle are accurately controlled by two external resistors and one capacitor.

1. Timer and Oscillator: The IC can operate as either a monostable (one-shot) timer or an astable (free-running) oscillator. Its mode of operation can be selected by configuring external components.

2. Timing Control: The device allows for precise control over timing intervals. In monostable mode, it generates a single pulse of a duration determined by external resistors and capacitors. In astable mode, it generates a continuous train of square wave pulses with a frequency determined by external components.

3. Wide Range of Timing Intervals: The LM555 can provide timing intervals ranging from microseconds to hours, depending on the values of the external resistors and capacitors used.

4. Adjustable Duty Cycle: In astable mode, the 555 allows for adjustment of the duty cycle (the ratio of the pulse width to the period) by altering the values of the external resistors and capacitors.


1. High-Current Drive Capability: 200 mA
2. Adjustable Duty Cycle
3. Temperature Stability of 0.005%/°C
4. Timing From μs to Hours
5. Turn off Time Less Than 2 μs

Ordering Information

LM555 Ordering Information

LM555 Ordering Information


Application Information

When the low signal input is applied to the reset terminal, the timer output remains low regardless of the threshold voltage or the trigger voltage. Only when the high signal is applied to the reset terminal, the timer’s output changes according to threshold voltage and trigger voltage.
When the threshold voltage exceeds 2/3 of the supply voltage while the timer output is high, the timer’s internal discharge transistor turns on, lowering the threshold voltage to below 1/3 of the supply voltage. During this time, the timer output is maintained low. Later, if a low signal is applied to the trigger voltage so that it becomes 1/3 of the supply voltage, the timer’s internal discharge transistor turns off, increasing the threshold voltage and driving the timer output again at high.


Block Diagram

LM555 Pinouts

LM555 Pinouts


• Precision Timing
• Pulse Generation
• Delay Generation
• Sequential Timing

Reference Homepage : LM555 Single Timer (onsemi.com)

LM555 Datasheet

LM555 pdf datasheet

Related Partnumber : LM555CM, LM555CMX, LM555CN


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