General-purpose dual bipolar timer
NE556 SA556 - SE556
General-purpose dual bipolar timers
Features
■ Low turn-off time ■ Maximum operating frequency grea...
Description
NE556 SA556 - SE556
General-purpose dual bipolar timers
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
Description
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.
N DIP14 (Plastic package)
D SO14 (Plastic micropackage)
Pin connections (top view)
Discharge 1 Threshold 2 Control Voltage 3
Reset 4 Output 5 Trigger 6
GND 7
14 VCC 13 Discharge 12 Threshold 11 Control Voltage 10 Reset 9 Output 8 Trigger
January 2009
Rev 2
1/16
www.st.com
16
Schematic diagrams
1
Schematic diagrams
Figure 1. Block diagram
VCC+ THRESHOLD CONTROL VOLTAGE
TRIGGER
RESET
5kW
COMP
R FLIP-FLOP
5kW
Q
COMP
S INHIBIT/ RESET
5kW
S
NE556 - SA556 - SE556
DISCHARGE OUT 1/2 NE556
Figure 2. Schematic diagram
THRESHOLD COMPARATOR
VCC
R1 4.7kW
R2
R3
830W 4.7kW
CONTR...
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