Texas Instruments SN74LV123APW

Overview

SN74LV123APW from Texas Instruments is a dual retriggerable monostable multivibrator IC with Schmitt-trigger inputs, designed for 2-V to 5.5-V operation. It generates precise, externally programmable output pulses (e.g., 90–110 µs at VCC = 3.3 V, Cext = 0.01 µF, Rext = 10 kΩ), supports mixed-mode voltage interfacing, and features glitch-free power-up reset and Ioff partial-power-down capability. It is used in timing control circuits for consumer audio/video systems and embedded interrupt conditioning.

For engineers reviewing the SN74LV123APW datasheet, SN74LV123APW pinout, SN74LV123APW application, or SN74LV123APW equivalent, key selection considerations include its retriggerable pulse width control via external RC network, 11 ns max propagation delay at 5 V, Schmitt-trigger noise immunity on A/B/CLR inputs, and TSSOP-16 package compatibility with legacy 'AHC123A/'AHCT123A footprints.

Technical Context

The SN74LV123APW integrates two independent monostable multivibrators, each triggered by edge-sensitive logic combinations of A, B, and CLR inputs. Pulse duration is determined by external Rext/Cext components using tw = K × RT × CT, where K ≈ 1.0 for CT ≥ 1000 pF and varies per Figure 3 for smaller capacitances.

It supports three trigger modes: falling edge on A (with B = L), rising edge on B (with A = H), or active-high CLR override. Retriggering extends pulse width up to 100% duty cycle, while CLR low terminates output early. All inputs feature Schmitt-trigger hysteresis for robust operation with slow or noisy signals.

Key Specifications

Pinout & Package

TSSOP-16 package (6.40 mm × 5.00 mm), thin shrink small-outline package with exposed pad not present; lead finish is matte tin.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC123A and 74AHC123, the SN74LV123APW uniquely balances wide VCC range (2–5.5 V), Ioff-enabled system-level power management, Schmitt-trigger noise resilience, and compact TSSOP-16 footprint - making it optimal for modern mixed-voltage embedded timing where reliability and layout density are critical.

Availability

SN74LV123APW is available at Aetrix Electronics and suitable for consumer electronics timing, industrial control signal conditioning, and embedded power sequencing requiring stable component supply and long-term lifecycle support.

Supply support for SN74LV123APW 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies with over 50 years of innovation in precision timing and logic solutions.

The SN74LV123APW belongs to TI's LV logic family, engineered for low-voltage, high-noise-immunity applications in consumer, industrial, and automotive systems where reliable edge-triggered timing is essential.

FAQ

What is the minimum external timing capacitance supported by the SN74LV123APW?

The SN74LV123APW supports external timing capacitance down to 10 pF, as verified in the datasheet's switching characteristics tables (e.g., Cext = 28 pF tested at VCC = 5 V). For values below 1000 pF, the multiplier factor K deviates from 1.0 and must be read from Figure 3 in the datasheet. The SN74LV123APW remains functional and stable at 10 pF, enabling nanosecond-range pulse generation when paired with appropriate Rext.

Does the SN74LV123APW support true 5-V TTL input compatibility?

Yes, the SN74LV123APW supports 5-V tolerant inputs across its full operating range (2–5.5 V VCC). Its VIH and VIL thresholds scale with VCC (e.g., VIH = 0.7×VCC min), and absolute input voltage rating is 0–5.5 V - allowing direct connection to 5-V TTL outputs without level-shifting circuitry, even when VCC = 3.3 V or 2.5 V.

How does the Ioff feature of the SN74LV123APW protect the system during partial power-down?

The Ioff feature in the SN74LV123APW disables all outputs when VCC = 0 V, blocking current flow from live I/O lines into the unpowered device. This prevents damaging back-current through input protection diodes - a critical safeguard in multi-rail systems where one supply may be active while another is off, such as in modular server or automotive ECU designs using the SN74LV123APW.

Can both monostable channels of the SN74LV123APW be triggered simultaneously without interference?

Yes, the two monostable channels in the SN74LV123APW are fully independent - each has dedicated A, B, CLR, Q, Q, Cext, and Rext/Cext terminals. Simultaneous triggering produces independent output pulses with no crosstalk, matched timing (Δtw ≤ ±1%), and identical electrical characteristics, as confirmed in the datasheet's functional block diagram and timing test conditions.

What is the maximum recommended value for Rext to maintain timing accuracy in the SN74LV123APW?

The datasheet specifies Rext up to 100 kΩ for stable operation, with timing characterization validated at 1 kΩ and 10 kΩ. At Rext = 100 kΩ and Cext = 100 pF, tw ≈ 10 µs (K ≈ 1.0); higher values increase sensitivity to leakage and parasitic capacitance. For production designs, TI recommends Rext ≤ 50 kΩ to ensure ±5% pulse width accuracy across temperature and process variation - a constraint explicitly applied to the SN74LV123APW in TI application note SCBA004.