The 74VHC123A/221AFT are high speed CMOS MONOSTABLE MULTIVIBRATOR fabricated with silicon gate C2MOS technology. There are two trigger inputs, A input (negative edge), and B input (positive edge). These inputs are valid for a slow rise/fall time signal (tr = tf = 1 s) as they are schmitt trigger inputs. This device may also be triggered by using CLR input (positive edge).After triggering, the output stays in a MONOSTABLE state for a time period determined by the external resistor and capacitor (RX, CX). A low level at the CLR input breaks this state. Limits for CX and RX are:External capacitor, CX: No limit External resistor, RX: VCC = 2.0 V more than 5 kΩ CC ≥ 3.0 V more than 1 kΩ An input protection circuit ensures that 0 to 5.5 V can be applied to the input pins without regard to the supply voltage. This device can be used to interface 5 V to 3 V systems and two supply systems such as battery back up. This circuit prevents device destruction due to mismatched supply and input voltages

Wide operating temperature range: Topr = -40 to 125 
High speed: Propagation delay time = 8.1 ns (typ.) at VCC = 5 V
Low power dissipation:
Standby state: 4.0 μA (max) at Ta = 25 
Active state: 750 μA (max) at Ta = 25 
High noise immunity: VNIH = VNIL = 28 % VCC (min)
Power-down protection is provided on all inputs.
Balanced propagation delays: tPLH ≈ tPHL
Wide operating voltage range: VCC(opr) = 2.0 V to 5.5 V
Pin and function compatible with 74HC123,74HC221 type