The NE556, SA556 and SE556 dual monolithic timing circuits are highly stable controllers capable of producing accurate time delays or oscillation. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor. For a stable operation as
an oscillator, the free running frequency and the duty cycle are both accurately controlled with two external resistors and one capacitor. The circuits may be triggered and reset on falling waveforms, and the output structure can source or sink up to 200 mA.
Features
Low turn-off time
Maximum operating frequency greater than 500 kHz
Timing from microseconds to hours
Operates in both astable and monostable modes
Output can source or sink up to 200 mA
Adjustable duty cycle
TTL compatible
Temperature stability of 0.005% per °C
NE556Pinout Configuration
Pin Number
Pin Name
Description
1,13
Discharge
Open collector output which discharges a capacitor between intervals (in phase with output). 7 I It toggles the output from high to low when voltage reaches 2/3 of the supply voltage
2,12
Threshold
Compares the voltage applied to the terminal with a reference voltage of 2/3 Vcc. The 6 I amplitude of voltage applied to this terminal is responsible for the set state of the flip-flop
3,11
Control Voltage
Controls the threshold and trigger levels. It determines the pulse width of the output 5 Voltage I waveform. An external voltage applied to this pin can also be used to modulate the output waveform
4,10
Reset
Negative pulse applied to this pin to disable or reset the timer. When not used for reset 4 I purposes, it should be connected to VCC to avoid false triggering
5,9
Out
This pin is normally connected to load as it is the only pin with output driven waveform
6,8
Trigger
Responsible for transition of the flip-flop from set to reset. The output of the timer depends 2 I on the amplitude of the external trigger pulse applied to this pin
7
Ground
Ground Reference Voltage 0V
14
Vcc
Supply Voltage (Typical = 5V, Maximum = 18V)
Features and Specifications
Two precision Timers in one single package
Typical operating voltage is +5V, can withstand a maximum of +18V.
The source/sink current of the output pin is 220mA
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