NA556DR

These devices provide two independent timing circuits in each package, of types NA555, NE555, SA555, or SE555. These circuits can operate in astable or monostable mode through external resistor-capacitor (RC) timing control. The basic timing provided by the RC time constant can be actively controlled by modulating the bias at the control voltage input. The threshold (THRES) and trigger (TRIG) levels are typically two-thirds and one-third of VCC, respectively. These levels can be changed by using the control voltage (CONT) terminal. When the trigger input is below the 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 goes low. The reset (RESET) input can override all other inputs and can be used to start 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 (DISCH) terminal and ground (GND).