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Encyclopedia > 555 timer IC
NE555 from Signetics in dual-in-line package
Schematic symbol of the 555 timer

The 555 timer is one of the most popular and versatile integrated circuits ever produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8). The 556 is a 14-pin DIP that combines two 555s on a single chip. The 558 is a 16-pin DIP that combines four, slightly modified, 555s on a single chip (DIS & THR are connected internally, TR is falling edge sensitive instead of level sensitive). Also available are ultra-low power versions of the 555 such as the 7555 and TLC555. The 7555 requires slightly different wiring using fewer external components and less power. For other uses, see Transistor (disambiguation). ... It has been suggested that Peak Inverse Voltage be merged into this article or section. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ... NE555 from Signetics in dual-in-line package DIP-8 is a commonly-used integral circuit package. ...

The 555 has three operating modes:

• Monostable mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, Frequency Divider,Capacitance Measurement, Pulse Width Modulation (PWM) etc
• Astable - Free Running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation, etc.
• Bistable mode: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bouncefree latched switches, etc.

## Contents

A monostable multivibrator is an electronic circuit that has two states, only one of which is stable. ... Pulse-width modulation of a signal or power source involves the modulation of its duty cycle, to either convey information over a communications channel or control the amount of power sent to a load. ... An astable multivibrator is an electronic circuit that has two states, neither one of which is stable. ... Oscillation is the periodic variation, typically in time, of some measure as seen, for example, in a swinging pendulum. ... External links LEd Category: TeX ... Something that is bistable can be resting in two states. ... In digital circuits, the flip-flop, latch, or bistable multivibrator is an electronic circuit which has two stable states and thereby is capable of serving as one bit of memory. ...

The connection of the pins is as follows:

Nr. Name Purpose
1 GND Ground, low level
2 TR A short pulse high → low on the trigger starts the timer
3 Q During a timing interval, the output stays at +VCC
4 R A timing interval can be interrupted by applying a reset pulse to low (0V)
5 CV Control voltage allows access to the internal voltage divider (2/3 VCC)
6 THR The threshold at which the interval ends (it ends if U.thr → 2/3 VCC)
7 DIS Connected to a capacitor whose discharge time will influence the timing interval
8 V+, VCC The positive supply voltage which must be between 5 and 15 V, high level

Using simply a capacitor and a resistor, the timing interval, i.e. the time during which the output stays low, can be adjusted to the need of the specific application. An example configuration is shown below: VCC can mean: Volvo Car Corporation Common-collector voltage (VCC) Vancouver Community College Valencia Community College Video Compact Cassette, an early name for Philips Video 2000 videocassette format ValueVision Channel, the previous name of ShopNBC Voice Call Continuity, a concept of IP Multimedia Subsystem Virtual Channel Connection [1] Vertical cross... See Capacitor (component) for a discussion of specific types. ... Resistor symbols (non-European) Resistor symbols (Europe, IEC) Axial-lead resistors on tape. ...

Example 555 schematic

The interval time t is given by Image File history File links 555-schem-2. ...

t = 1.1RC

which is the time it takes to charge C to 63% of the applied voltage (exact figure: (1-1/e)V). See RC circuit for an explanation of this effect. resistor-capacitor circuit (RC circuit), or RC filter or RC network, is one of the simplest analogue electronic filters. ...

In the astable mode, the high time from each pulse is given by

$high = 0.693 cdot (R1 + R2) cdot C$

and the low time from each pulse is given by

$low = 0.693 cdot R2 cdot C$

where R1 and R2 are the values of the resistor in ohms and C is the value of the capacitor in farads. A multimeter can be used to measure resistance in ohms. ... Examples of various types of capacitors. ...

It has a voltage varying gate. The gate is open when the output voltage is low, and the gate is closed when output voltage is high.

## Specifications

These specifications apply to the NE555. Other 555 timers can have better specifications depending on the grade (military, medical, etc).

 Supply voltage (VCC) 4.5 to 15 V Supply current (VCC = +5 V) 3 to 6 mA Supply current (VCC = +15 V) 10 to 15 mA Output current (maximum) 200 mA Power dissipation 600 mW Operating temperature 0 to 70 °C

## Derivatives

Many pin-compatible variants, including CMOS versions, have been built by various companies. The 555 is also known under the following type numbers: For other uses, see CMOS (disambiguation). ...

Manufacturer Model Remark
ECG Philips ECG955M
Exar XR-555
Fairchild Semiconductor NE555/KA555
Harris HA555
Intersil SE555/NE555/ICM7555
Lithic Systems LC555
Maxim ICM7555 CMOS from 2V
Motorola MC1455/MC1555
National Semiconductor LM1455/LM555/LM555C
National Semiconductor LMC555 CMOS from 1.5V
NTE Sylvania NTE955M
Raytheon RM555/RC555
RCA CA555/CA555C
Sanyo LC7555
Texas Instruments SN52555/SN72555; TLC555
USSR K1006ВИ1
Zetex ZSCT1555 down to 0.9 V

Fairchild Semiconductor introduced the first commercially available integrated circuit (although at almost the same time as one from Texas Instruments), and would go on to become one of the major players in the evolution of Silicon Valley in the 1960s. ... Harris Corporation NYSE: HRS is an international communications equipment company that produces wireless equipment, electronic systems, and both terrestrial and spaceborne antennas for use in the government, defense, and commercial sectors. ... Intersil Corporation NASDAQ: ISIL produces integrated circuits and semiconductors. ... Maxim Integrated Products NASDAQ: MXIM (including its subsidiary Dallas Semiconductor) is a semiconductor company that designs and manufactures analog and mixed-signal integrated circuits. ... Motorola Inc. ... Categories: Electronics companies of the United States | Companies based in California | Corporation stubs ... Categories: Electronics companies of the United States | Companies based in California | Corporation stubs ... On the morning of July 2, 1956, an explosion involving scrap Thorium occurred at the Sylvania Electric Products Metallurgical Laboratory. ... Raytheon Company (NYSE: RTN) is a major American defense contractor and industrial corporation with core manufacturing concentrations in defense systems and defense and commercial electronics. ... RCA, formerly an acronym for the Radio Corporation of America, is now a trademark owned by Thomson SA through RCA Trademark Management S.A., a company owned by Thomson. ... Sanyo Electric Co. ... Texas Instruments (NYSE: TXN), better known in the electronics industry (and popularly) as TI, is an American company based in Dallas, Texas, USA, renowned for developing and commercializing semiconductor and computer technology. ...

Results from FactBites:

 The 555 Timer IC (and the related 556 IC) (948 words) The 555 timer integrated circuit is one of the most popular and useful integrated circuits of all time. A lengthy tutorial here on the 555 timer and how to use it would be a duplication of effort since at  http://www.uoguelph.ca/~antoon/gadgets/555.htm  there an excellent tutorial, which you should study to learn how this IC works. All of the timing calculations for circuits using the 555 timer are based on the response of a series R-C circuit with a step or constant voltage input, and exponential output taken across the capacitor.
 555 timer IC - Wikipedia, the free encyclopedia (540 words) The 555 is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. The 555 timer is one of the most popular and versatile integrated circuits ever produced. Bistable mode: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used.
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