Texas Instruments SN74LV123ADB

Overview

SN74LV123ADB from NXP Semiconductors is a dual retriggerable monostable multivibrator in SSOP16 package, operating from 1.0 V to 5.5 V supply. It features Schmitt-trigger inputs (nA/nB), direct active-LOW reset (nRD), and programmable pulse width via external REXT/CEXT networks. Used for precise timing control in digital logic interfaces, such as debouncing switches or generating controlled delays in industrial control sequencers.

For engineers reviewing the SN74LV123ADB datasheet, SN74LV123ADB pinout, SN74LV123ADB application, or SN74LV123ADB equivalent, this page delivers verified functional identity, confirmed pin roles, validated timing behavior across voltage ranges, and real-world substitution guidance - all grounded in NXP's Rev. 8 product data sheet (2016).

Technical Context

The SN74LV123ADB implements two independent monostable circuits, each with three trigger modes: negative-edge on nA, positive-edge on nB, and asynchronous reset on nRD. Pulse width is set by external REXT and CEXT components, supporting retriggering to extend output duration up to 100% duty cycle without oscillation.

Schmitt-trigger action on nA and nB inputs ensures robust noise immunity against slow-rising/falling signals, while the reset path operates independently of timing components. Propagation delays range from 14 ns (VCC = 5.5 V) to 120 ns (VCC = 1.2 V) for nRD→nQ, and from 18 ns to 120 ns for nA/nB→nQ, per NXP's dynamic characterization.

Key Specifications

Pinout & Package

SN74LV123ADB uses the SSOP16 (SOT338-1) package: plastic shrink small outline, 16 leads, 5.3 mm body width, 0.65 mm lead pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC123APW and 74HC123D, SN74LV123ADB uniquely combines 1.0 V operation, Schmitt-trigger inputs, and −40 °C to +125 °C qualification - making it the only option for wide-voltage, high-noise, high-temperature timing in modern embedded systems.

Availability

SN74LV123ADB is available at Aetrix Electronics and suitable for industrial automation, automotive body control modules, and test equipment requiring stable component supply across extended temperature ranges and mixed-voltage interfaces.

Supply support for SN74LV123ADB 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

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications.

The SN74LV123ADB belongs to NXP's LV logic family, designed specifically for low-voltage, high-noise-immunity digital timing in space-constrained, thermally demanding environments.

FAQ

What is the minimum supply voltage required for reliable operation of the SN74LV123ADB?

The SN74LV123ADB is guaranteed to function down to VCC = 1.0 V, with static characteristics specified from VCC = 1.2 V. At 1.0 V, inputs are recognized as HIGH or LOW relative to GND or VCC, enabling compatibility with ultra-low-power 1.2 V microcontrollers and energy-harvesting systems where SN74LV123ADB maintains full functionality.

Can the SN74LV123ADB be used with 5 V logic systems?

Yes, the SN74LV123ADB supports VCC up to 5.5 V and accepts TTL input levels when VCC is between 2.7 V and 3.6 V. For direct 5 V logic interfacing, use external pull-up resistors or level translators on nA/nB/nRD inputs to ensure VIH/VIL thresholds are met - SN74LV123ADB itself tolerates 5 V supply and drives 5 V-compatible outputs.

How does the retriggering function work in the SN74LV123ADB?

The SN74LV123ADB allows output pulse extension by applying new trigger edges (on nA or nB) before the initial monostable period expires. Each retrigger resets the internal timing counter, enabling arbitrarily long pulses - useful for applications like manual override latches or adaptive delay generation where SN74LV123ADB replaces multiple discrete timers.

What is the purpose of the Schmitt-trigger inputs on the SN74LV123ADB?

Schmitt-trigger action on nA and nB inputs provides hysteresis (typically >1 V at VCC = 3.3 V), making SN74LV123ADB highly tolerant of slow-rising or noisy signals - such as those from mechanical switches, long PCB traces, or unfiltered sensor outputs - preventing multiple false triggers that would occur with standard CMOS inputs.

Is the SN74LV123ADB pin-compatible with other 74-series monostables?

Yes, the SN74LV123ADB is pin and function compatible with the 74HC123 and 74HCT123, sharing identical pin assignments and logic behavior. This allows drop-in replacement in existing designs while delivering lower voltage operation, improved noise immunity, and extended temperature range - all without modifying PCB layout or firmware.