SN74HC123DR – TEXAS INSTRUMENTS

The SN74HC123DR is a dual retriggerable monostable multivibrator (one-shot) integrated circuit from Texas Instruments, packaged in a space-saving 8-pin PDIP. It operates from a wide supply voltage range of 2V to 6V, offering significant design flexibility. Each of the two independent timers features a timing capacitor input and a timing resistor input, allowing precise control over the output pulse width (typically 0.1µs to 100ms) through external component selection. Retriggerability ensures that a new timing cycle begins upon receiving a trigger pulse before the previous cycle completes. The output is a high-impedance open-collector, requiring an external pull-up resistor for proper operation. Propagation delays are typically under 20ns, making it suitable for high-speed applications._x000D_
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The HC CMOS technology provides low power consumption and high noise immunity, making it ideal for battery-powered or noisy environments. Common applications include pulse shaping, timing generation, debouncing switches, and generating precise time delays in various digital control systems. Its dual configuration allows for efficient implementation of multiple timing functions within a single chip, reducing board space and component count compared to using discrete components or single timer ICs. Designers should carefully consider the timing capacitor and resistor values for precise pulse width control and account for the open-collector output’s need for an external pull-up.