ICM/ (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest go to ). The Maxim ICM and ICM are respectively single . with the descriptive excerpts from the original manufacturer’s data sheet have been included in this. ICM | Counter/Time Base ICs | Renesas Datasheet The ICM and ICM are CMOS RC timers providing significantly improved performance.

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The timer IC is an integrated circuit chip used in a variety of 75555pulse generation, and oscillator applications. The can be used to provide time delays, as an oscillatorand as a flip-flop element. Derivatives provide two or four timing circuits in one package. Introduced in [3] by Signetics[4] the is still in widespread use due to its low price, ease of use, and stability. It is now made by many companies in the original bipolar and in low-power CMOS technologies.

As of [update]it was estimated that 1 billion units were manufactured every year. The IC was designed in by Hans R. He became interested in tuners such as a gyrator and a phase-locked loop PLL.

He designed an oscillator for PLLs such that the frequency did not depend on the power supply voltage or temperature. However, Signetics laid off half of its employees, and the development was frozen due to a recession. Camenzind proposed the development datasgeet a universal circuit based on the oscillator for PLLs, and asked that he would develop it alone, borrowing their equipment instead of having his pay cut in half.

Other engineers argued datadheet product could be built from existing parts, but the marketing manager bought the idea. Among 5xx numbers that were assigned for analogue ICs, the special number “” was chosen. Camenzind also taught circuit design at Northeastern University in the morning, and went to the same university at night to get a master’s degree in Business Administration.

There was no problem, so it proceeded to layout design. A few days later, he got the idea of using a direct resistance instead of a constant current source, and found that it worked. The change decreased the required 9 pins to 8, so the IC could be fit in an 8-pin package instead of a pin package. This design passed the second design review, and the prototype was completed in October Its 9-pin copy had been already released by another company founded by an engineer who attended the first review and retired from Signetics, but they withdrew it soon after the was released.

The timer was manufactured datashset 12 companies in and it became the best selling product. Depending on the manufacturer, the standard package includes 25 transistors2 diodes and 15 resistors on a silicon chip installed in an 8-pin dual in-line package DIP These were available in both high-reliability metal can T package and inexpensive epoxy plastic V package packages. The ICM datasheet claims that it usually doesn’t require a “control” capacitor and in many cases does not require a decoupling capacitor across the power supply datahseet.

For good design practices, a decoupling capacitor should be included, however, because noise produced by the timer or variation in power supply voltage might interfere with other parts of a circuit or influence its threshold voltages.


The internal block diagram and schematic of the timer are highlighted with the same color across all three drawings to clarify how the chip is implemented: The typical pinout of the and IC packages are as follows: Pinout of single timer 8 pins [1] [2].

Pinout of dual timer 14 pins conceptually two timers [18] [2]. In astable mode, the timer puts out a continuous stream of rectangular pulses having a specified frequency. Resistor R 1 is connected between V CC and the discharge pin pin 7 and another resistor R 2 is connected between the discharge pin pin 7and the trigger pin 2 and threshold pin dwtasheet pins that share a common node. Hence the capacitor is charged through R 1 and R 2and discharged only through R 2since pin 7 has low impedance to ground during output low intervals of the cycle, therefore discharging the capacitor.

In the datasheeh mode, the frequency of the pulse stream depends on the values of R 1R 2 and C:.

Otherwise the output low time will be greater than calculated above. To have an output high time shorter than the low time i.

This bypasses R 2 during the high part of the cycle so that the high interval depends only on R 1 and C, with an adjustment based the voltage drop across the diode. The low time will be the same as above, 0. With the bypass diode, the high time is. The equation reduces to the expected 0. Some manufacturers’ parts will hold the output state to dtaasheet it was when RESET is taken low, others will send the output either high or low.

This circuit is similar to using an inverter 5755 as an oscillator, but with fewer components than the astable configuration, and a much higher power output than a TTL or CMOS gate.

The operation of the diode when connected is explained above. The duty cycle then varies with the potentiometer at a constant frequency.

A series resistor of ohms must be added to each R1 and R2 to limit peak current of the transistor within when R1 and R2 are at minimum level. This method of adding a diode id a restriction of choosing R1 and R2 values.

An alternate way is to add a JK flip-flop to the output of non-symmetrical square wave generator. But, with this the output frequency is one half of the timer.

555 Timer IC

The output pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C. Assume initially the output of the monostable is zero, the output of flip-flop Q bar is 1 so that the discharging transistor is on and voltage across capacitor is zero. Now the capacitor charges towards supply voltage Vcc. The output of flip-flop remains unchanged therefore the output is 0.

The cycle repeats continuously. The charging and discharging of capacitor depends on the time constant RC. While using the timer IC in monostable mode, the main disadvantage is that the time span between any two triggering pulses must be greater than the RC time constant.

In bistable mode, the timer acts as a basic flip-flop. The trigger and reset inputs pins 2 and 4 respectively on a are held high via pull-up resistors while the threshold input datashfet 6 is grounded. Thus configured, pulling the trigger momentarily to ground acts as a ‘set’ and transitions the output pin pin 3 to V CC high state. Pulling the reset input to ground acts as a ‘reset’ and transitions the output pin to ground low dtaasheet.


No timing capacitors are required in a bistable configuration. Pin 7 daasheet is left unconnected, or may be used as an open-collector output. A timer can be used to create a Schmitt trigger which converts a noisy input into a clean digital output.

timer IC – Wikipedia

The input signal should be connected through a series capacitor which then connects to the trigger and threshold pins. The reset pin is tied to V CC. These specifications apply to the bipolar NE Other timers can have different 77555 depending on the grade military, medical, etc. These values should be considered “ball park” values, instead the current official datasheet from the exact manufacturer of each chip should be consulted for parameter limitation recommendations.

The dual timer is available in through hole packages as DIP datxsheet. Numerous companies have manufactured one or more variants of the, timers over the past decades as many different part numbers. The following is a partial list: Over the years, numerous IC companies have merged.

The new parent company inherits everything from the previous company then datasheets and chip logos are changed over a period of time to the new company. This information is useful when tracking down datasheets for older parts.

timer 7555 datasheet

Instead of including every related company in the above table, only one name is listed, and the following list can be used to determine the relationship. The dual version is called It features two complete s in a 14 pin package. Only the two power supply pins are shared between the two timers. The quad version is called It has four reduced-functionality timers in a 16 pin package four complete timer circuits would have required 26 pins.

Currently the is not manufactured by any major chip companies possibly not by any companiesthus the should be treated as obsolete. Parts are still available from a limited number of sellers as ” new old stock ” N. Partial list of differences between and chips: The Apple II microcomputer used a quad timer in monostable or “one-shot” mode to interface up to four “game paddles” or two joysticks to the host computer.

The center wiper pin of the potentiometer was connected to i Axis wire in the datashfet and one end of the potentiometer was connected to the 5 Volt wire in the cord.

The joystick potentiometer acted as a variable resistor in the RC network. A wide pulse represented the full-right joystick position, for example, while a narrow pulse represented the full-left joystick position.

From Wikipedia, the free encyclopedia. Archived PDF from the original on June 28, Retrieved June 28, Archived from the original on April 5, Retrieved June 29, Retrieved 27 December Archived from the original on January 9, Volume VI – Experiments”.

Digest of Technical Papers. Archived from the original on October 4, Archived PDF from the original on June 29, Retrieved June 30, datqsheet Archived PDF from datzsheet original on June 30, Retrieved from ” https: Electronic oscillators Linear integrated circuits.