Texas Instruments SN74AHC123AMDREPG4

Overview

SN74AHC123AMDREPG4 from Texas Instruments is a dual retriggerable monostable multivibrator IC operating from 2 V to 5.5 V, featuring Schmitt-trigger inputs on A, B, and CLR pins, ±1% output pulse-duration variation between channels, and extended temperature range (–55°C to 125°C). It delivers programmable pulse widths via external R_ext/C_ext networks and supports edge-triggered operation with active-high or active-low gated logic inputs - used in precision timing control for industrial sensor interfaces and power sequencing circuits.

For engineers reviewing the SN74AHC123AMDREPG4 datasheet, SN74AHC123AMDREPG4 pinout, SN74AHC123AMDREPG4 application, or SN74AHC123AMDREPG4 equivalent, key selection considerations include its dual-channel retriggerability, ±1% inter-channel pulse-matching, SOIC-16 package compatibility, and guaranteed glitch-free power-up reset behavior across –55°C to 125°C.

Technical Context

The SN74AHC123AMDREPG4 implements two independent monostable multivibrators with identical timing architecture: each uses an external R_ext/C_ext network to set pulse duration (t_w), supports three trigger modes (A↓/B↑, A↑/B↓, or CLR↑ with A low/B high), and features Schmitt-trigger input hysteresis to reject slow or noisy transitions. Pulse width is calculated as t_w = K × R_ext × C_ext, where K = 1 for C_ext ≥ 1000 pF.

Retriggering occurs when a new valid input edge arrives before t_w expires, extending the output pulse; CLR overrides all triggers and forces immediate output reset. Propagation delays range from 5.3 ns (t_PHL, V_CC = 5 V, CL = 15 pF) to 27.5 ns (t_PLH, V_CC = 3.3 V, CL = 50 pF), with inter-channel pulse-duration variation limited to ±1% under matched external components.

Key Specifications

Pinout & Package

SN74AHC123AMDREPG4 is housed in a 16-pin SOIC (D) package with 1.27 mm pitch, JEDEC MS-012 compliant, and RoHS-compliant NiPdAu lead finish. The package supports automated placement and reflow up to 260°C (MSL Level-1).

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHCT123AD and CD74HC123M96, SN74AHC123AMDREPG4 uniquely combines extended temperature operation, ultra-low I_CC, and ±1% inter-channel pulse matching - making it the only option qualified for mission-critical timing in aerospace, defense, and industrial control systems requiring long-term supply continuity.

Availability

SN74AHC123AMDREPG4 is available at Aetrix Electronics and suitable for industrial power sequencing, avionics watchdog timers, and automotive sensor signal conditioning requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for SN74AHC123AMDREPG4 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 high-reliability logic solutions, with over 50 years of innovation in timing, power management, and signal chain technologies.

The SN74AHC123A product line delivers radiation-tolerant, extended-temperature monostable multivibrators for mission-critical timing in defense electronics, space systems, and industrial automation where deterministic pulse generation and long-term supply assurance are essential.

FAQ

What is the maximum external timing capacitance supported by SN74AHC123AMDREPG4?

The SN74AHC123AMDREPG4 supports external timing capacitors up to 28 µF, as validated in the datasheet's switching characteristics table (tw = 240 ns with C_ext = 28 µF, R_ext = 2 kΩ). Larger values risk excessive energy storage during power-down, potentially damaging input protection diodes unless clamped externally. For stable operation, TI recommends C_ext ≤ 1 µF unless specific retriggering or long-pulse requirements justify larger values with proper discharge path design.

Does SN74AHC123AMDREPG4 require external pull-up or pull-down resistors on unused inputs?

Yes - all unused inputs of SN74AHC123AMDREPG4 must be held at V_CC or GND to ensure proper device operation and prevent floating-node-induced current leakage or erratic triggering. TI's application report SCBA004 explicitly states that unconnected A, B, or CLR inputs can cause increased ICC and unpredictable output behavior. Pull-up/pull-down values of 10 kΩ to 100 kΩ are typical, selected to dominate over input leakage while minimizing power draw.

Can SN74AHC123AMDREPG4 generate asymmetric pulse widths on Q and Q̅ outputs?

No - SN74AHC123AMDREPG4 generates strictly complementary Q and Q̅ outputs with identical pulse duration (t_w) and propagation delays (t_PLH/t_PHL). The internal logic guarantees matched rise/fall times and pulse widths within ±1% variation between channels, but not between Q and Q̅ of the same channel. Any observed asymmetry would result from external loading imbalance or PCB trace mismatch, not device functionality.

What is the minimum retrigger time (t_MIR) for SN74AHC123AMDREPG4?

The minimum input retrigger time (t_MIR) for SN74AHC123AMDREPG4 is 0.3 × t_w, where t_w is the programmed pulse width. For example, with t_w = 100 µs, t_MIR = 30 µs. This ensures the internal timing circuit fully recovers before accepting a new trigger. Experimental data in Figure 3 of the datasheet confirms this relationship holds across V_CC = 2 V to 5.5 V and TA = –55°C to 125°C.

Is SN74AHC123AMDREPG4 pin-compatible with SN74AHC123AMDREP?

Yes - SN74AHC123AMDREPG4 is a tape-and-reel variant of SN74AHC123AMDREP with identical SOIC-16 (D) package, pinout, electrical specifications, and thermal ratings. The "G4" suffix denotes TI's green packaging standard (lead-free, RoHS-compliant NiPdAu finish) and does not affect functionality, timing, or compatibility. Both share the same top-side marking "AHC123AEP" and MSL Level-1 rating.