Nexperia USA Inc. 74HCT221D,112

Overview

74HCT221D,112 from Nexperia is a dual non-retriggerable monostable multivibrator in SO16 package, providing two independent edge-triggered timing channels with direct active-LOW reset. It operates from 4.5 V to 5.5 V, delivers pulse widths defined by t_W = 0.7 × C_EXTR_EXT, and features Schmitt-trigger inputs on nB pins for jitter-free triggering from slow-rising signals-used in digital debouncing, pulse shaping, and delay generation in industrial control logic.

For engineers reviewing the 74HCT221D,112 datasheet, 74HCT221D,112 pinout, 74HCT221D,112 application, or 74HCT221D,112 equivalent, key selection criteria include non-retriggerable behavior, TTL-compatible input thresholds, ±5% typical pulse width variance, and SO16 thermal derating (12.4 mW/K above 110 °C).

Technical Context

This device implements two independent monostable circuits, each with separate negative-edge (nA) and positive-edge (nB) trigger inputs, plus dedicated active-LOW reset (nRD). Pulse width is externally set via R_EXT/C_EXT networks connected to pins 15/14 (Channel 1) and 7/6 (Channel 2), with internal compensation ensuring stability across V_CC (4.5–5.5 V) and temperature (−40 °C to +125 °C).

Each channel outputs complementary signals (nQ, nQ) with propagation delays as low as 21 ns (nB→nQ, V_CC = 4.5 V) and recovery time of 12 ns after reset. Schmitt-trigger action on all nB inputs provides hysteresis (typ. 0.8 V at V_CC = 4.5 V), enabling reliable operation with noisy or slow-transition waveforms.

Key Specifications

Pinout & Package

74HCT221D,112 is housed in a plastic small outline package (SO16, SOT109-1) with 16 leads, 3.9 mm body width, and gull-wing lead form suitable for surface-mount reflow assembly.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar monostable multivibrator applications.

Compared with 74HCT221D,112, the 74HC221D,653 offers broader supply flexibility but sacrifices noise immunity, while SN74LS221N delivers legacy pinout compatibility at the cost of timing precision and thermal stability-making the HCT variant optimal for new designs requiring robust, accurate one-shot timing.

Availability

74HCT221D,112 is available at Aetrix Electronics and suitable for industrial motor control, automotive body electronics, test equipment signal conditioning, and medical diagnostic instrumentation requiring stable component supply across extended temperature ranges.

Supply support for 74HCT221D,112 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Nexperia is a global semiconductor expert focused on high-volume, high-reliability logic, discrete, and MOSFET solutions, with manufacturing rooted in process excellence and automotive-grade quality systems.

The 74HCT series targets mixed-signal interface applications requiring TTL-compatible inputs and CMOS efficiency, specifically designed for industrial automation, automotive subsystems, and instrumentation where noise immunity and timing predictability are critical.

FAQ

What is the minimum external resistor value supported for pulse width configuration?

The datasheet specifies R_EXT down to 2 kΩ at V_CC = 5.0 V. Using lower values risks exceeding the 25 mA absolute maximum output current rating during timing node discharge, potentially degrading pulse width accuracy or causing latch-up. For sub-microsecond pulses, verify timing with actual R/C tolerances and board parasitics.

Can both monostable channels be triggered simultaneously without interference?

Yes-each channel (1 and 2) operates fully independently. Triggering Channel 1 via 1A/1B has no effect on Channel 2's state or timing, and vice versa. The shared V_CC and GND pins are decoupled internally, and dynamic current spikes are isolated per channel per the static/dynamic characterization data.

Is external capacitor CEXT required for basic operation?

Yes-CEXT is mandatory for pulse width definition. The device lacks internal timing capacitance; omitting CEXT results in undefined or zero-duration output. Per Figure 5, CEXT must be connected externally between nCEXT and GND, with recommended values from 28 pF to 1 μF depending on desired t_W range and stability requirements.

How does the reset function interact with an ongoing output pulse?

Asserting nRD LOW terminates the current output pulse immediately, forcing nQ LOW and nQ HIGH within 26 ns (t_PHL). This action is asynchronous and overrides all trigger inputs. After reset release (nRD HIGH), the monostable remains in quiescent state until next valid edge on nA or nB-no retriggering occurs during the reset interval.