The NE555 from Texas Instruments is the industry-standard precision timer IC capable of producing accurate time delays or oscillation. Operating from 4.5V to 16V, it can sink or source up to 200mA at the output and supports both monostable (one-shot) and astable (free-running) modes with timing from microseconds to hours.<\/p>\n
Product Overview The NE555 from Texas Instruments is the industry-standard precision timer IC capable of producing accurate time delays or oscillation. Operating from 4.5V to 16V, it can sink or source up to 200mA at the output and supports both monostable (one-shot) and astable (free-running) modes with timing from microseconds to hours. Key Specifications Supply […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[13,55],"tags":[],"chip_brand":[138],"class_list":["post-6535","post","type-post","status-publish","format-standard","hentry","category-integrated-circuits-ics","category-transistors","chip_brand-ti"],"acf":{"brief_explanation":"Precision timer IC, 4.5-16V, 200mA output, mono\/astable, PDIP-8","date_code":"","package_case":"PDIP-8","in_stock":18000,"datasheet":"https:\/\/www.ti.com\/lit\/ds\/symlink\/ne555.pdf","price":"$0.35","product_introduction":"The NE555 from Texas Instruments is the most iconic timer IC in electronics history, designed by Hans Camenzind at Signetics in 1972. Over a billion units are still shipped annually, making it one of the highest-volume ICs ever produced. The device can operate in monostable mode to generate precise time delays (t = 1.1 \u00d7 R \u00d7 C) controlled by a single external resistor and capacitor, or in astable mode to generate free-running square waves with independently controllable frequency and duty cycle using just two resistors and one capacitor. The 200mA output capability allows direct driving of LEDs, small relays, and speakers without additional driver circuitry. The internal voltage divider sets the trigger threshold at 1\/3 VCC and the threshold at 2\/3 VCC, both adjustable through the CONT pin. The NE555 variant is specified for 0\u00b0C to 70\u00b0C operation, while the SA555 extends to -40\u00b0C to 85\u00b0C and the SE555 to -55\u00b0C to 125\u00b0C.","working_principle":"The NE555 internal circuit consists of three 5k\u03a9 resistors forming a voltage divider, two comparators, an SR flip-flop, a discharge transistor, and a push-pull output stage. The voltage divider sets 1\/3 VCC at the trigger comparator and 2\/3 VCC at the threshold comparator. In monostable mode, the trigger input (TRIG) falling below 1\/3 VCC sets the flip-flop, driving the output high and turning off the discharge transistor. The external capacitor charges through R until the threshold (THRES) reaches 2\/3 VCC, which resets the flip-flop, driving the output low and turning on the discharge transistor to rapidly discharge the capacitor. The output pulse width is T = 1.1 \u00d7 R \u00d7 C. In astable mode, the capacitor charges through R1+R2 and discharges through R2 only, creating a free-running oscillator with f = 1.44 \/ ((R1 + 2R2) \u00d7 C) and duty cycle = (R1+R2)\/(R1+2R2). The CONT pin allows external modulation of the 2\/3 VCC threshold for PWM or VCO applications. The RESET pin (active low) overrides all other inputs and forces the output low.","pin_description":"
| Pin<\/th> | Name<\/th> | Function<\/th><\/tr> | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1<\/td> | GND<\/td> | Ground reference<\/td><\/tr> | |||||||||||||||
| 2<\/td> | TRIG<\/td> | Trigger input (sets output high when < 1\/3 VCC)<\/td><\/tr> | |||||||||||||||
| 3<\/td> | OUT<\/td> | Output (sink\/source up to 200mA, push-pull)<\/td><\/tr> | |||||||||||||||
| 4<\/td> | RESET<\/td> | Active-low reset (overrides all inputs, forces output low)<\/td><\/tr> | |||||||||||||||
| 5<\/td> | CONT<\/td> | Control voltage (2\/3 VCC internal, modifiable for PWM\/VCO)<\/td><\/tr> | |||||||||||||||
| 6<\/td> | THRES<\/td> | Threshold input (resets output when > 2\/3 VCC)<\/td><\/tr> | |||||||||||||||
| 7<\/td> | DISCH<\/td> | Discharge transistor (open collector, connects to GND when output low)<\/td><\/tr> | |||||||||||||||
| 8<\/td> | VCC<\/td> | Power supply (4.5V ~ 16V)<\/td><\/tr><\/table>","application_scenarios":"The NE555 is used in LED flasher circuits where the astable mode generates a square wave at visible frequencies (1-10Hz) with R and C values chosen for the desired blink rate. For debounce circuits, the monostable mode creates a clean pulse of defined width from a noisy switch input. In PWM motor speed control, the CONT pin modulates the threshold level, varying the output duty cycle in proportion to a control voltage. For tone generation, two 555 timers can be cascaded \u2014 one in astable mode for the tone frequency and one for the envelope \u2014 creating simple musical effects. In power-on delay circuits, the monostable mode holds a reset line for a defined period after power-up, allowing supply voltages to stabilize before the system starts.","alternative_models":"
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