These devices are precision timing circuits capable of producing accurate time delays or oscillation. In the time-delay or monostable mode of operation,the timed interval is controlled by a single external resistor and capacitor network. In the astable mode of operation, the frequency and duty cycle can be controlled independently with two external resistors and a single external capacitor.
The threshold and trigger levels normally are two-thirds and one-third,respectively, of V CC . These levels can be altered by use of the control-voltage terminal. When the trigger input falls below the trigger level, the flip-flop is set,and the output goes high.If the trigger input is above the trigger level andthe threshold input is above the threshold level, the flip-flop is reset and the output is low. The reset (RESET) input can over ride all other inputs and can be used to initiate a new timing cycle.When RESET goes low, the flip-flop is reset,and the output goes low. When the output is low, a low-impedance path is provided between discharge(DISCH) and ground.
The output circuit is capable of sinking or sourcing current up to 200mA.Operation is specified for suppliesof 5V to 15V.With a 5-V supply,output levels are compatible with TTL inputs.