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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2. Iris Biometrics
3. RFID Reader


SE555 Datasheet PDF Download

SE555 pdf


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

What is 74LS244? – Octal Buffer and Line Driver

What is 74LS244?

This is a type of integrated circuit chip known as a buffer/line driver. It is designed to provide high-speed signal buffering and amplification in a variety of electronic applications.

1. High-speed signal transfer: It is designed to operate at high speeds, making it suitable for use in applications that require fast signal transfer.

2. Low power consumption: The chip is designed to operate with a low power consumption, making it suitable for use in battery-powered devices.

3. High output current: It can provide a high output current, making it suitable for use in applications that require a strong signal.

4. Easy to use: This is easy to use and requires minimal external components, making it a popular choice for beginners and hobbyists.

5. Multiple outputs: The chip can provide eight buffered outputs.

Part Number: 74LS244

Function: Octal Buffers and Line Drivers With 3-State Outputs

Package: DIP 20 Pin, LCCC 20 Pin Type

Manufacturer: Texas Instruments

Image and pinouts :

74LS244 Datasheet Pinout


These octal buffers and line drivers are designed specifically to improve both the performance and density of three-state memory address drivers, clock drivers, and bus-oriented receivers and transmitters. The designer has a choice of selected combinations of inverting and noninverting outputs, symmetrical, active-low output-control (G)\ inputs, and complementary output-control (G and G\) inputs. These devices feature high fan-out, improved fan-in, and 400-mV noise margin. The SN74LS’ and SN74S’ devices can be used to drive terminated lines down to 133 Ω.

Advantages Vs Disadvantages

1. High-speed signal transfer makes it useful for fast signal processing.

2. Low power consumption makes it ideal for use in battery-powered devices.

3. Easy to use and requires minimal external components.

4. Multiple outputs make it suitable for use in a variety of applications.


1. The 74LS244 is an older technology and may not be suitable for use in some modern electronic applications that require more advanced features and specifications.

2.  It has a limited operating temperature range.

3. It may not be suitable for use in high-voltage applications.


  • 3-State Outputs Drive Bus Lines or Buffer Memory Address Registers
  • PNP Inputs Reduce DC Loading
  • Hysteresis at Inputs Improves Noise Margins



• Servers

• LED Displays

• Network Switches

• Telecom Infrastructure

• Motor Drivers

Some similar: 74LS541, 74LS245, and 74LS573.

74LS244 Datasheet

74LS244 pdf