SN74AHCT123ADR

The SNx4AHCT123A is a dual retriggerable monostable multivibrator. This device is an edge-triggered multivibrator with three methods available to control the output pulse duration. The output pulse duration can be programmed by selecting external resistor and capacitor values. The external timing capacitor must be connected between Cext and Rext/Cext (positive terminal), and the external resistor must be connected between Rext/Cext and VCC. For variable pulse duration, a variable external resistor can be connected between Rext/Cext and VCC. In addition, the output pulse duration can be shortened by driving CLR low. Pulse triggering occurs at specific voltage levels and is independent of the input pulse transition time. Schmitt-trigger inputs on A, B, and CLR provide sufficient hysteresis to accommodate slow input transition rates while ensuring glitch-free triggering at the output. After triggering, the basic pulse duration can be extended by retriggering via the active-low (A) or active-high (B) gating inputs. Driving CLR low terminates the pulse duration; the CLR input can be used to override inputs A or B. For given external timing components, output pulse duration variation between devices is typically less than ±0.5%. During power-up, the Q output is in the low state and the Q̄ output is in the high state. The outputs are glitch-free and no reset pulse is required.

Key features

• TTL-compatible inputs
• Schmitt-trigger circuits on A, B, and CLR inputs for slow input transition rates
• Edge-triggered via active-high or active-low gating logic inputs
• Retriggerable for very long output pulses
• Output pulse terminable via override clear
• Latch-up performance exceeds 100mA per JESD 78 Class II