NE555P | Texas Instruments

Single Precision Timer, NE555P, Texas Instruments

The NE555P device is precision timing circuit capable of producing accurate time delay or oscillation. In time-delay or monostable operating mode, the timed interval is controlled by a single external resistor and capacitor network. In the astable mode of operation, the frequency and duty cycle is controlled independently with two external resistor and a single external capacitor. Each timer has a trigger level equal to approximately one-third of the supply voltage and a threshold level equal to approximately two-thirds of the supply voltage. These levels can be altered by use of the control voltage pin (CONT).

When the trigger input (TRIG) is less than the trigger level, the flip-flop is set and the output goes high. If TRIG is greater than the trigger level and the threshold input (THRES) is greater than the threshold level, the flip-flop is reset and the output is low. The reset input (RESET) overrides all other inputs and is used to initiate a new timing cycle. If RESET is low, the flip-flop is reset and the output is low. Whenever the output is low, a low-impedance path is provided between the discharge pin (DISCH) and the ground pin (GND). Tie all unused inputs to an appropriate logic level to prevent false triggering.

Features

• Timing from microseconds to hours
• Astable or monostable operation
• Adjustable duty cycle
• TTL-compatible output can sink or source up to 200mA