Texas Instruments SN74LV123APWT

Overview

SN74LV123APWT from Texas Instruments is a dual retriggerable monostable multivibrator IC with Schmitt-trigger inputs, operating from 2 V to 5.5 V supply, delivering ≤11 ns propagation delay at 5 V, ±1% pulse-duration matching between channels, and programmable output pulse width up to 100% duty cycle via external R/C network - used for edge-sensitive timing control in digital interrupt conditioning and signal debouncing circuits.

For engineers reviewing the SN74LV123APWT datasheet, SN74LV123APWT pinout, SN74LV123APWT application, or SN74LV123APWT equivalent, key selection considerations include its dual-channel retriggerability, Ioff partial-power-down support, mixed-mode voltage operation on all ports, and TSSOP-16 package compatibility with legacy 'AHC123A/'AHCT123A footprints.

Technical Context

The SN74LV123APWT implements two independent monostable multivibrators, each triggered by combinations of A (falling-edge active-low), B (rising-edge active-high), or CLR (active-high override) inputs. Pulse duration is externally set via Rext/Cext network, with tw = K × RT × CT where K ≈ 1.0 for CT ≥ 1000 pF.

Each channel features Schmitt-trigger inputs enabling jitter-free response to slow or noisy transitions, glitch-free power-up reset (Q low, Q high), and Ioff protection preventing backflow during partial power-down. Timing is fully characterized across –40°C to 125°C and 2 V–5.5 V VCC.

Key Specifications

Pinout & Package

TSSOP-16 package (6.40 mm × 5.00 mm), thermally enhanced for industrial temperature range (–40°C to 125°C), pin-compatible with SN74LV123A family variants including SOIC, SSOP, SO, and VQFN.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC123APW and 74HC123D,653, the SN74LV123APWT uniquely combines Ioff-enabled partial-power-down, Schmitt-triggered CLR, and sub-11 ns speed at 5 V - making it optimal for modern low-power, mixed-voltage, and noise-prone embedded timing applications.

Availability

SN74LV123APWT is available at Aetrix Electronics and suitable for desktop PCs or notebook PCs, digital video cameras (DVC), server PSU, and wireless headsets, keyboard, and mice requiring stable component supply across extended temperature and voltage ranges.

Supply support for SN74LV123APWT 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 logic solutions, with over 50 years of innovation in high-reliability timing and interface ICs.

The SN74LV123A product line delivers low-voltage, retriggerable monostable functionality for precision edge-triggered timing in consumer, industrial, and computing systems - designed for robustness, interoperability, and seamless migration from legacy 74AHC/74AHCT families.

FAQ

What is the minimum external timing capacitance supported by SN74LV123APWT?

The SN74LV123APWT supports external timing capacitance down to 28 pF (per datasheet Figure 7.9). At Cext = 28 pF and Rext = 2 kΩ, typical pulse duration is 240 ns with CL = 50 pF load. For values below 1000 pF, the multiplier factor K deviates from 1.0 and must be read from Figure 3 in the datasheet. The device does not specify a hard lower limit, but practical stability requires ≥10 pF with appropriate layout.

Does SN74LV123APWT support both rising- and falling-edge triggering on the same input pair?

Yes, SN74LV123APWT supports configurable edge triggering per channel: rising-edge mode when 1A is held low and 1B receives a high-going transition; falling-edge mode when 1B is held high and 1A receives a low-going transition. This dual-mode flexibility is confirmed in the Function Table (Section 9.4) and allows one hardware design to serve multiple timing configurations without redesign.

How does the Ioff feature function in SN74LV123APWT during system power-down?

In SN74LV123APWT, the Ioff circuitry disables all outputs when VCC = 0 V, blocking current flow into or out of I/O pins even if external signals remain active. This prevents damaging back-current through protection diodes - critical in hot-swap or modular power architectures. Ioff is specified at ±5 µA maximum leakage (Section 7.5), verified across –40°C to 125°C.

Can SN74LV123APWT generate identical pulse widths on both channels simultaneously?

Yes, SN74LV123APWT guarantees ±1% pulse-duration matching (Δtw) between Channel 1 and Channel 2 under identical Rext/Cext conditions and temperature (Section 7.9). This tight matching is process-trimmed and tested - enabling precise dual-event timing in applications like differential clock stretching or mirrored signal conditioning where skew must be minimized.

What is the maximum recommended external timing resistance for SN74LV123APWT?

The datasheet specifies Rext up to 1 MΩ (Section 7.3), but practical limits arise from leakage and noise. At VCC ≥ 3 V, Rext = 10 kΩ is used in timing examples (Section 7.9–7.11); for longer pulses, Rext = 100 kΩ with Cext = 0.1 µF yields ~1 ms tw. Values above 500 kΩ increase susceptibility to parasitic leakage and require guarded layout - TI recommends verifying stability with actual board-level testing.