SE556D

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...