NE555N timer & circuits | pinout, projects onsemi

NE555N Pinout Equivalent

NE555N Picture

NE555N is a bipolar integrated circuit manufactured by Texas Instruments that can produce high-precision timing pulses. Internally, it includes a threshold comparator, a trigger comparator, and an RS trigger.It is composed of four parts of circuits, such as device and output circuit. It can be connected to a small number of external resistor components to form a timing trigger circuit, a pulse width modulation circuit, and a tone frequency oscillators and other circuits. It is widely used in toys, signal traffic, automatic control and so on.But when chips are in short supply or design adjustments are planned, electronics engineers need to look for their replacement models. The following sections of this article describe the NE555N’s pin functions and replaceable chips.

Here’s the detailed pin definition and functional description of the NE555N

Alternative model recommendation

The needs of users may include to look for compatible models produced by different vendors, or alternatives with improved performance, power consumption, packaging, etc. You need to ensure that the recommended alternative models are compatible with the NE555N in the pin layout and basic functionality, while potentially focusing on cost, availability, or specific application requirements.Here I recommend alternative chips according to different needs.

TLC555, LMC555(e.g., battery-powered equipment):

Need high precision timing, we recommend SA555/SE555 (TI):Higher temperature stability (±2% frequency error), suitable for precision timing circuits.Operating voltage 4.5V-16V, compatible with NE555N.

When users need high speed response , we recommend TS555 (ST):Faster switching speed (rise/fall time ≤100ns), suitable for high frequency oscillator.Still bipolar design, output current 200mA.

ICM7555 Picture

SE555 (TI) Picture

TS555 (ST) Picture

ne555n projects

NE555N is developed by the U.S. Signetics Corporation in 1972 to replace the mechanical timer of the medium-sized integrated circuits, because the input is designed with three 5kΩ resistors and named; internal structure of the RS flip-flop, comparator, voltage comparator of the three main digital circuit modules, the external pins are mainly for the purpose of interconnecting with other chips to form a usable circuit. 555 The timer has a wide range of supply voltage, can work in 4.5V ~ 16V, 7555 (and 555 process is different from the use of complementary metal oxide process) can work in 3 ~ 18V, the output drive current of about 200mA, and thus its output can be compatible with the TTL, CMOS, or analogue circuit levels.NE555 was designed to provide a simple and convenient timer solution, but due to its excellent performance, it has been used in a wide range of circuits. The NE555 was originally designed to provide a simple and convenient timer solution, but because of its excellent performance and cheap price, it is widely used in various aspects; for example, timing control circuits, clock generator circuits, frequency measurement circuits and so on.
Next we look at a square wave (50% high and 50% low level waveforms) generator using the NE555N.

NE555N Implementation of Square Wave Generator

When the circuit is powered on, the power supply through RA and RB to capacitor C charging, so the NE555N pin2 and pin6 voltage with the capacitor internal charge becomes more and more increase, when the capacitor on the voltage is less than 1/3 of the supply voltage (VCC is the supply voltage), the output is high; when the capacitor on the voltage between 1/3 VCC to 2/3 VCC, to maintain the current state (the last state is what, this time also continue to maintain); when the capacitor on the voltage is greater than 2/3 VCC, the output low level at the same time transistor Q1 conduction capacitor began to discharge, that is, the process of charging the above in turn to go through. This can be achieved by periodic interaction of high and low levels.
But between this out of the waveform is not stable and may not be able to achieve a square wave, then we need to calculate the charging and discharging time according to the formula, the formula is shown in the figure below: after calculation we found that we want to achieve a duty cycle of 50% of the waveform required for the capacitor resistance were RA = 15k, RB = 68k, C = 10uf; simulation is shown in the following figure: you can find that you can indeed achieve a square wave! signal.

Calculation formula chart

simulation graphics