Nexperia USA Inc. 74AHC123AD,112

Overview

74AHC123AD,112 from Nexperia is a dual retriggerable monostable multivibrator with independent reset inputs, operating from 2.0 V to 5.5 V supply, featuring Schmitt-trigger inputs, overvoltage-tolerant I/O up to 5.5 V, and specified for -40 °C to +125 °C. It generates programmable output pulses via external REXT/CEXT networks and supports pulse extension via edge-triggered retriggering on either input (nA or nB), enabling precise timing control in digital logic systems.

For engineers reviewing the 74AHC123AD,112 datasheet, 74AHC123AD,112 pinout, 74AHC123AD,112 application, or 74AHC123AD,112 equivalent, key selection criteria include its dual-channel retriggerable architecture, TTL- or CMOS-level compatibility (AHC variant), SO16 package thermal performance, and direct reset functionality for deterministic pulse termination in noise-prone environments.

Technical Context

This device implements two independent monostable circuits, each with separate negative-edge (nA) and positive-edge (nB) trigger inputs, active-low direct reset (nRD), complementary outputs (nQ/nQ), and external timing network connections (nREXT/CEXT, nCEXT). Pulse width tW is programmable per channel using CEXT ≥ 10 nF and REXT = 1–5 kΩ, with typical values of 100 ns (CEXT = 28 pF, REXT = 2 kΩ) to 1.15 ms (CEXT = 0.1 μF, REXT = 10 kΩ) at VCC = 5.0 V.

Each monostable supports retriggering during an active output pulse to extend duration indefinitely-enabling 100 % duty factor generation-and immediate termination via LOW-going edge on nRD. Input hysteresis (Schmitt action), overvoltage tolerance, and latch-up immunity (>100 mA) ensure robust operation in mixed-voltage and electrically noisy industrial interfaces.

Key Specifications

Pinout & Package

74AHC123AD,112 is housed in a plastic small outline package (SO16, SOT109-1) with 16 leads, 3.9 mm body width, and standard 1.27 mm lead pitch. The package supports automated assembly and provides adequate thermal dissipation (Ptot = 500 mW at Tamb ≤ 110 °C) for continuous operation in compact industrial PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74AHCT123AD,112, the AHC variant offers superior noise immunity in mixed-signal systems due to higher input hysteresis, while SN74LVC1G123DBVR sacrifices channel count and reset capability for footprint reduction-making it unsuitable for applications requiring concurrent, independently controlled timing events with deterministic abort.

Availability

74AHC123AD,112 is available at Aetrix Electronics and suitable for motor control timing, industrial PLC input debouncing, and power supply sequencing requiring stable component supply across extended temperature ranges and mixed-voltage interfaces.

Supply support for 74AHC123AD,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 delivering high-performance logic, discrete, and MOSFET solutions optimized for efficiency, reliability, and manufacturability in automotive, industrial, and consumer applications.

The 74AHC123A product line delivers advanced retriggerable monostable functionality with enhanced ESD robustness and wide supply range, designed specifically for timing-critical industrial control, power management, and noise-immune digital interface applications.

FAQ

What is the minimum external capacitor value required for stable operation?

The datasheet specifies CEXT ≥ 10 nF for predictable pulse width scaling (tW ≈ CEXT × REXT). Using smaller values (e.g., 28 pF) yields fixed short pulses (100–240 ns) but introduces greater sensitivity to parasitic capacitance and temperature drift. For repeatable timing, always use ≥10 nF ceramic capacitors with low ESL, placed adjacent to pins 6/7 and 14/15.

Can both channels share the same REXT/CEXT network?

No-each channel requires dedicated REXT and CEXT components. Pins 14/15 (Channel 1) and 6/7 (Channel 2) are electrically isolated timing nodes. Sharing components would cause crosstalk, unpredictable pulse widths, and potential failure to retrigger correctly. The SO16 layout physically separates these nets to prevent layout-induced coupling.

How does the direct reset (nRD) interact with ongoing retriggering?

An active LOW on nRD terminates the output pulse immediately-even mid-retrigger cycle-with a maximum reset propagation delay of 16.5 ns (VCC = 5.5 V, CL = 50 pF). This override is asynchronous and unconditional, making it suitable for emergency stop or fault-clearing logic where deterministic timing abort is mandatory.

Is the 74AHC123AD,112 pin-compatible with older 74LS123 variants?

No-while functional behavior is similar, pin assignments differ significantly. The 74AHC123AD uses SO16 pinout with dedicated 1CEXT/2CEXT and shared 1REXT/CEXT/2REXT/CEXT nodes, whereas 74LS123 uses different pin mapping (e.g., separate R and C pins per channel, no Schmitt inputs). PCB redesign and schematic update are required for migration.