HD74LS221P

HD74LS221 Dual Monostable Multivibrators REJ03D0458–0300 Rev.3.00 Jul.15.2005 This multivibrator features a negative-transition-triggered input and a positive-transition-triggered input either of which can be used as an inhibit input. Pulse triggering occurs at a particular voltage level and is not directly related to the transition time of the input pulse. Schmitt-trigger input circuitry (TTL hysteresis) for B input allows jitter-free triggering from inputs with transition rates as slow as 1 V/s, providing the circuit with excellent noise immunity of typically 1.2 V. A high immunity to VCC noise of typically 1.5 V is also provided by internal latching circuitry. Once fired, the outputs are independent of further transitions of the A and B inputs and are a function of the timing components, or the output pulses can be terminated by the overriding clear. Input pulses may be of any duration relative to the output pulse. Output rise and fall times are TTL compatible and independent of pulse length. Typical triggering and clearing sequence are illustrated as a part of the switching characteristics waveforms. Pulse width stability is achieved through internal compensation and is virtually independent of VCC and temperature. In most applications, pulse stability will only be limited by the accuracy of external timing components. Jitter-free operation is maintained over the full temperature and VCC range for more than six decades of timing capacitance (10 pF to 10 µF) and more ...