SE555 Datasheet PDF – Precision Timer – TI

What is SE555?

This is Precision Timer. It is a popular integrated circuit (IC) timer that is widely used in electronic circuits. It is also known as NE555, LM555, or simply 555 timer. The IC is a versatile timer that can be used to generate precise and stable time delays, oscillations, and pulse-width modulation signals.

Part Number: SE555

Function: Precision Timer

Package: PDIP, SOP, TSSOP, SOIC 8 Pin

Manufacturer: Texas Instruments

SE555 datasheet


These devices are precision timing circuits capable of producing accurate time delays or oscillation. In the time-delay or monostable mode of operation, the timed interval is controlled by a single external resistor and capacitor network. In the astable mode of operation, the frequency and duty cycle can be controlled independently with two external resistors and a single external capacitor.

The threshold and trigger levels normally are two-thirds and one-third, respectively, of Vcc. These levels can be altered by use of the control-voltage terminal. When the trigger input falls below the trigger level, the flip-flop is set, and the output goes high. If the trigger input is above the trigger level and the threshold input is above the threshold level, the flip-flop is reset and the output is low.

The reset (RESET) input can override all other inputs and can be used to initiate a new timing cycle. When RESET goes low, the flip-flop is reset, and the output goes low. When the output is low, a low-impedance path is provided between discharge (DISCH) and ground.

The output circuit is capable of sinking or sourcing current up to 200 mA. Operation is specified for supplies of 5 V to 15 V. With a 5-V supply, output levels are compatible with TTL inputs.

Block Diagram

SE555 Block diagram


1. Timing From Microseconds to Hours
2. Astable or Monostable Operation
3. Adjustable Duty Cycle
4. TTL-Compatible Output Can Sink or Source up to 200 mA

It has a number of useful features, including a wide operating voltage range (typically 4.5V to 18V), low power consumption, and high output current capability. It can be used in a variety of modes, as mentioned earlier, and can generate a range of output signals, including square waves, pulses, and ramps.


The SE555 timer is a simple and versatile IC that is widely available and inexpensive. Its ease of use, low cost, and wide range of applications make it a popular choice for both hobbyists and professionals. Additionally, the timer is capable of driving a wide range of loads, including LEDs, motors, and relays, making it useful in a variety of circuits.


While the timer has many advantages, it also has a few drawbacks. For example, it is not suitable for high-frequency applications due to its limited frequency range (typically up to a few hundred kilohertz). Additionally, the output of the timer can be affected by variations in temperature and supply voltage, which can lead to inaccuracies in timing.

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SE555 Datasheet PDF Download

SE555 pdf


Other data sheets are available within the file: NA555, NE555, SA555, NA555D, NA555DG4