The NA556N is a Precision Timer can be operated in the astable and the monostable mode with external resistor-capacitor (RC) timing control. The basic timing provided by the RC time constant can be controlled actively by modulating the bias of the control-voltage input. The threshold and trigger levels normally are 2/3rd and 1/3rd respectively of VCC. This level can be altered by using the control voltage terminal. When the trigger input falls below trigger level the flip-flop is set and the output goes high. If the trigger input is above the trigger level and the threshold input is above the threshold level the flip-flop is reset and the output is low. The reset input can override 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 the discharge terminal and ground.
The LM556CN/NOPB is a highly-stable Dual Timer capable of producing accurate time delays or oscillation. The LM556 device is a dual-timing version of the LM555 device. Timing is provided by an external resistor and capacitor for each timing function. The two timers operate independently of each other, sharing only VCC and ground. The circuits may be triggered and reset on falling waveforms. The output structures may sink or source 200mA.