NE555 SA555 - SE555 General-purpose single bipolar timers Features Low turn-off time Maximum operating frequency greater than 500 kHz Timing from microseconds to hours N DIP8 Operates in both astable and monostable (Plastic package) modes Output can source or sink up to 200 mA Adjustable duty cycle TTL compatible D Temperature stability of 0.005% per C SO8 (Plastic micropackage) Description The NE555, SA555, and SE555 monolithic timing circuits are highly stable controllers capable of Pin connections producing accurate time delays or oscillation. In (top view) 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 1 8 both accurately controlled with two external 2 7 resistors and one capacitor. The circuit may be triggered and reset on falling 36 waveforms, and the output structure can source or sink up to 200 mA. 5 4 1 - GND 5 - Control voltage 2 - Trigger 6 - Threshold 3 - Output 7 - Discharge 4 - Reset 8 - V CC January 2012 Doc ID 2182 Rev 6 1/20 www.st.com 20Schematic diagrams NE555 - SA555 - SE555 1 Schematic diagrams Figure 1. Block diagram + V CC 5k COMP DISCHARGE THRESHOLD R CONTROL VOLTAGE FLIP-FLOP Q 5k COMP OUT TRIGGER S INHIBIT/ RESET 5k S RESET Figure 2. Schematic diagram 2/20 Doc ID 2182 Rev 6