74VHC123A: Dual Retriggerable Monastable Multivibrator

The VHC123A is an advanced high speed CMOS Monostable Multivibrator fabricated with silicon gate CMOS technology. It achieves the high speed operation similar to equivalent Bipolar Schottky TTL while maintaining the CMOS low power dissipation. Each multivibrator features both a negative, A, and a positive, B, transition triggered input, either of which can be used as an inhibit input. Also included is a clear input that when taken low resets the one-shot. The VHC123A can be triggered on the positive transition of the clear while A is held low and B is held high. The output pulse width is determined by the equation: PW = (Rx)(Cx); where PW is in seconds, R is in ohms, and C is in farads.     Limits for Rx and Cx are:      External capacitor, CxNo limit      External resistors, Rx VCC = 2.0V, 5 kohm min      VCC > 3.0V, 1 kohm min     An input protection circuit ensures that 0 to 7V can be applied to the input pins without regard to the supply voltage. This device can be used to interface 5V to 3V systems and two supply systems such as battery back up. This circuit prevents device destruction due to mismatched supply and input voltages.

Features

• High Speed: t_PD = 8.1 ns (typ) at T_A = 25°C
• Low Power Dissipation:I_CC = 4 µA (Max) at T_A = 25°C
• Active State: I_CC = 600 µA (Max) at T_A = 25°C
• High Noise Immunity: V_NIH = V_NIL = 28% V_CC (min)
• Power down protection is provided on all inputs
• Pin and function compatible with 74HC123A

Application Notes