74HCT221D SMD IC SO16

74HCT221D SMD IC SO16

The 74HC/HCT221 stands as a high-speed CMOS logic device, offering a dual monostable multivibrator with reset functionality. Compatible with low power Schottky TTL (LSTTL) standards and conforming to JEDEC standard no. 7A, these devices ensure seamless integration into existing systems.

Each 74HC/HCT221 multivibrator module is equipped with an active LOW-going edge input (nA) and an active HIGH-going edge input (nB), both of which serve as enable inputs. Pulse triggering occurs at specific voltage thresholds, independent of input pulse transition times. The inclusion of Schmitt-trigger input circuitry for the nB inputs guarantees jitter-free triggering, even with inputs featuring slow transition rates, thereby enhancing noise immunity.

Once triggered, the outputs (nQ, nQ) operate independently of further transitions of nA and nB inputs, relying solely on the timing components. The duration of output pulses can be controlled and terminated using the overriding active LOW reset inputs (nRD). Input pulses of varying durations relative to the output pulse are supported.

Pulse width stability is maintained through internal compensation mechanisms, ensuring consistency across different VCC levels and temperature ranges. The relationship governing output pulse width is defined by a formula involving external timing components.

Pin assignments for the “221” mirror those of the “123,” facilitating easy substitution in systems not utilizing retrigger functionality. This can be achieved simply by adjusting the values of REXT and/or CEXT components as needed.

In essence, the 74HC/HCT221 offers reliability, versatility, and ease of integration, making it a preferred choice for applications demanding precision timing and robust performance.

Features

• Pulse width variance is typically less than ± 5%
• Pin-out identical to “123”
• Overriding reset terminates output pulse
• nB inputs have hysteresis for improved noise immunity
• Output capability: standard (except for nREXT/CEXT)
• ICC category: MSI

Package Includes

• 1 x 74HCT221D SMD IC SO16