Texas Instruments SN74LVC1G123DCTT

Overview

SN74LVC1G123 from Texas Instruments is a single retriggerable monostable multivibrator with Schmitt-trigger inputs, designed for 1.65 V to 5.5 V operation. It supports mixed-mode voltage translation, delivers ≤8 ns propagation delay at 3.3 V, and enables pulse durations from nanoseconds to milliseconds via external R/C network - used in switch debouncing, timing control, and edge-sensitive event capture in consumer electronics.

For engineers reviewing the SN74LVC1G123 datasheet, SN74LVC1G123 pinout, SN74LVC1G123 application, or SN74LVC1G123 equivalent, key selection criteria include retriggerable pulse extension capability, Ioff-enabled live insertion support, Schmitt-trigger input hysteresis for slow-edge immunity, and NanoFree™ package compatibility with high-density PCB layouts.

Technical Context

The SN74LVC1G123 implements a CMOS-based retriggerable monostable architecture where output pulse duration is externally set by Rext and Cext connected to dedicated pins (Rext/Cext and Cext). Triggering occurs on either rising edge of B (with A low), falling edge of A (with B high), or rising edge of CLR (with A low and B high).

Schmitt-trigger inputs on A and B provide ≥0.3×VCC hysteresis, enabling jitter-free response to slow-rising/falling signals. The Ioff feature disables outputs during partial power-down, preventing back-drive current - critical for hot-swap and multi-rail systems.

Key Specifications

Pinout & Package

SN74LVC1G123 is packaged in an 8-pin SSOP (DCT) with 2.95 mm × 2.80 mm body size, optimized for space-constrained applications requiring manual assembly or automated pick-and-place.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LVC1G123, the DBVR variant offers identical functionality in a smaller VSSOP package for space-critical layouts, while the MC74VHC1G123DTT1G provides wider supply range but sacrifices speed and Schmitt hysteresis consistency - making SN74LVC1G123 optimal for mixed-voltage, high-speed, noise-immune timing.

Availability

SN74LVC1G123 is available at Aetrix Electronics and suitable for switch debouncing, power sequencing control, event pulse stretching, and edge-detection interface applications requiring stable component supply across industrial, consumer, and embedded design cycles.

Supply support for SN74LVC1G123 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 focused on analog and embedded processing technologies, serving automotive, industrial, personal electronics, and communications markets.

The SN74LVC1G123 belongs to TI's LVC logic family, engineered for low-voltage operation, mixed-signal interoperability, and robustness in real-world signal conditioning and timing applications.

FAQ

What is the minimum external timing capacitance supported by the SN74LVC1G123?

The SN74LVC1G123 supports external timing capacitances down to 10 pF, as verified in Figure 5-3 through Figure 5-5 of the datasheet. At VCC = 3.3 V and Rext = 1 kΩ, a 10 pF Cext yields a nominal pulse width of ~225 ns. Lower values risk timing instability due to parasitic capacitance dominance, so 10 pF is the practical lower limit for predictable operation.

Can the SN74LVC1G123 operate with a 1.65 V supply and still meet its specified tpd?

Yes, the SN74LVC1G123 is fully characterized down to 1.65 V. At this minimum VCC, the maximum propagation delay (tpd) is 52 ns (per Table 5.7, CL = 15 pF, –40°C to 85°C), which remains within datasheet limits. Performance degrades predictably with voltage, but all timing and drive specifications are guaranteed across the full 1.65–5.5 V range.

How does the CLR pin function in retriggerable mode for the SN74LVC1G123?

In retriggerable mode, the CLR pin serves dual roles: it terminates the current output pulse when driven low (asynchronous clear), and it can also initiate a new pulse when driven high while A is low and B is high. This dual functionality enables both emergency pulse cancellation and alternative trigger path - confirmed in Table 7-1 and Section 7.4 of the SN74LVC1G123 datasheet.

Is the SN74LVC1G123 compatible with 5 V input signals when powered from a 3.3 V supply?

Yes, the SN74LVC1G123 accepts input voltages up to 5.5 V regardless of VCC, as stated in Section 5.1 (Absolute Maximum Ratings) and Section 5.3 (Recommended Operating Conditions). This overvoltage-tolerant input design allows direct interfacing with 5 V logic while operating at 3.3 V, eliminating level-shifters in mixed-voltage systems.

What is the purpose of the Rext/Cext pin on the SN74LVC1G123?

The Rext/Cext pin is a bidirectional node connecting both the external timing resistor (to VCC) and the external timing capacitor (to Cext). It forms the RC time constant that determines output pulse duration. As specified in Section 3 and Figure 5-1, this pin must not be tied directly to VCC or GND - doing so disables timing functionality and violates recommended operating conditions.