The 74VHC221A is an advanced high-speed CMOS Monostable Multivibrator fabricated with silicon gate CMOS technology. It achieves high-speed operation similar to equivalent Bipolar Schottky TTL while maintaining 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 VHC221A can be triggered on the positive transition of the clear while A is held LOW and B is held HIGH. The VHC221A is non-retriggerable and therefore cannot be retriggered until the output pulse times out. 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.
The 74VHC221A is a high‑speed CMOS dual non‑retriggerable monostable multivibrator with low power dissipation. It offers both negative‑edge (A) and positive‑edge (B) trigger inputs, a clear input, and is pin‑compatible with the 74HC221A family. The device can interface 5 V to 3 V systems and includes input protection for 0‑7 V.
The datasheet provides ordering information, electrical characteristics, timing diagrams, and mechanical dimensions for the SOIC, SOP and TSSOP packages. Recommended operating conditions, absolute maximum ratings, and typical performance parameters such as propagation delay and output pulse width are listed.
| Typical tap delay | 8.1 ns (Typ.) at VCC = 5 V |
|---|---|
| Maximum supply current | 4 µA (Max.) at Ta = 25 °C |
| High noise immunity | Vin = Vih = 28 % VCC (Min.) |
| Pin compatibility | Compatible with 74HC221A |
| Recommended supply voltage | 2.0 V to 5.5 V |
| Input high level | 2.0 V (Min.) |
| Output pulse width formula | PW = Rx × Cx |
The recommended supply voltage range is 2.0 V to 5.5 V.
The output pulse width is the product of the external resistor and capacitor: PW = Rx × Cx.
The device draws a maximum of 4 µA at 25 °C.