The document describes the 74HC/HCT221 dual non-retriggerable monostable multivibrator with reset. The pulse width variance is typically less than ± 5%. The pin-out is identical to '123'. Overriding reset terminates the output pulse. The nB inputs have hysteresis for improved noise immunity. Output capability is standard (except for nREXT/CEXT). ICC category: MSI.
The Philips 74HC/HCT221 is a high‑speed Si‑gate CMOS dual non‑retriggerable monostable multivibrator. Each section provides an active low‑going edge input (nA) and an active high‑going edge input (nB) that can also serve as enable inputs. The device offers jitter‑free triggering, excellent noise immunity, and an overriding reset that terminates the output pulse.
The datasheet details pin assignments, functional tables, timing diagrams, DC and AC characteristics, typical output pulse width versus timing capacitance, and power‑down protection recommendations. It also includes ordering information and package outlines for designers.
| Pulse width variance | < +5% |
|---|---|
| Output capability | standard (except for NRext/Cext) |
| Icc category | MSI |
| Propagation delay (typical) | 15 ns |
| C input capacitance | 3.5 pF |
Pins 1 and 9 are the negative‑edge trigger inputs (nA), while pins 2 and 10 are the positive‑edge trigger inputs (nB).
The output pulse width is defined by tw = 0.7 × Cext × Rext.
The typical input capacitance is 3.5 pF.