1. General description
The 74HC123; 74HCT123 is a dual retriggerable monostable multivibrator with reset. The basic
output pulse width is programmed by selection of external components (REXT and CEXT). Once
triggered this basic pulse width may be extended by retriggering either of the edge triggered
inputs (nA or nB). By repeating this process, the output pulse period (nQ = HIGH, nQ = LOW)
can be made as long as desired. Alternatively, an output delay can be terminated at any time by
a LOW-going edge on input nRD. Inputs include clamp diodes. This enables the use of current
limiting resistors to interface inputs to voltages in excess of VCC.
Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slower input rise
and fall times.
2. Features and benefits
• Wide supply voltage range from 2.0 V to 6.0 V
• CMOS low power dissipation
• High noise immunity
• Latch-up performance exceeds 100 mA per JESD 78 Class II Level B
• Complies with JEDEC standards:
• JESD8C (2.7 V to 3.6 V)
• JESD7A (2.0 V to 6.0 V)
• Input levels:
• For 74HC123: CMOS level
• For 74HCT123: TTL level
• DC triggered from active HIGH or active LOW inputs
• Retriggerable for very long pulses up to 100 % duty factor
• Direct reset terminates output pulse
• Schmitt-trigger action on all inputs except for the reset input
• ESD protection:
• HBM JESD22-A114F exceeds 2000 V
• MM JESD22-A115-A exceeds 200 V
• Multiple package options
• Specified from -40 °C to +85 °C and from -40 °C to +125 °C