Texas Instruments SNJ54123J

Overview

SNJ54123J from Texas Instruments is a retriggerable monostable multivibrator in a 16-pin ceramic dual in-line package (CDIP), designed for precise pulse generation and timing control in military-grade systems. It features two independent monostable circuits, TTL-compatible inputs/outputs, 10 ns typical propagation delay, 25 ns minimum output pulse width, and operates across –55°C to +125°C.

For engineers reviewing the SNJ54123J datasheet, SNJ54123J pinout, SNJ54123J application, or SNJ54123J equivalent, this device serves critical timing functions in radar pulse shaping, digital test equipment synchronization, and missile guidance subsystems where retriggerability, wide temperature range, and radiation-tolerant packaging are mandatory.

Technical Context

The SNJ54123J implements two identical retriggerable monostable multivibrators with edge-triggered inputs (A and B) and complementary outputs (Q and Q̅). Each circuit uses internal RC timing networks with external R_EXT and C_EXT components to set pulse width, supporting adjustable delays from 30 ns to >10 s. The retriggerable architecture allows new triggers to reset and extend the output pulse before timeout.

It conforms to the SN54LS123 functional specification and is fully compatible with standard TTL logic levels. Input thresholds are V_IL = 0.8 V max and V_IH = 2.0 V min; output drive capability is I_OH = –0.4 mA at V_OH = 2.4 V and I_OL = 8 mA at V_OL = 0.5 V under full military temperature range.

Key Specifications

Pinout & Package

Ceramic Dual In-Line Package (CDIP), 16-pin, hermetically sealed, with 0.3-inch body width and 0.1-inch lead pitch. Pin 1 identified by notch or dot; leads are straight and solder-dip compatible.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SNJ54123J, SNJ54LS123J offers lower power and better noise margins in the same military-grade package, while SN74LS123N sacrifices environmental robustness for cost and RoHS compliance - making SNJ54123J the sole choice for flight-critical timing where retriggerability and extreme temperature resilience are non-negotiable.

Availability

SNJ54123J is available at Aetrix Electronics and suitable for radar pulse shaping, digital test equipment, missile guidance interface, and secure communication sync requiring stable component supply across extended temperature ranges and long-lifecycle programs.

Supply support for SNJ54123J 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 with over 60 years of analog and logic IC innovation, serving defense, aerospace, industrial, and automotive markets with high-reliability components.

The SNJ54123J belongs to TI's military-qualified 54-series logic family, engineered specifically for mission-critical timing applications demanding guaranteed performance across extreme environmental conditions and long service life.

FAQ

What is the maximum operating temperature for SNJ54123J?

The SNJ54123J is rated for continuous operation from –55°C to +125°C, validated per MIL-STD-883 methods. This full military temperature range ensures reliable timing performance in jet engine bays, missile canisters, and satellite payload bays where ambient extremes exceed commercial-grade limits. The SNJ54123J maintains specified propagation delay and output drive strength across this entire span.

Does SNJ54123J support retriggering during an active output pulse?

Yes, SNJ54123J is explicitly designed as a retriggerable monostable multivibrator. A new trigger applied to either A or B input during an active Q output pulse will immediately reset the internal timing circuit and extend the output pulse duration by the full R_EXT/C_EXT-defined interval - enabling adaptive pulse generation in real-time signal processing systems.

What package type and lead finish does SNJ54123J use?

SNJ54123J uses a 16-pin ceramic dual in-line package (CDIP, J suffix) with tin-lead (SNPB) lead finish. This hermetically sealed package meets MIL-PRF-38535 Class V requirements and provides superior moisture resistance, thermal cycling endurance, and long-term solderability compared to plastic alternatives - critical for aerospace and defense deployments.

Can SNJ54123J be used with modern 3.3 V logic systems?

No - SNJ54123J is a 5 V TTL device with V_CC = 4.5–5.5 V and TTL input thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V). Direct interfacing with 3.3 V logic requires level-shifting circuitry. For native 3.3 V compatibility, consider newer alternatives like the SN74LVC1G123, but note these lack military qualification and extended temperature range.

Are pins 8 and 9 on SNJ54123J internally connected?

No - pins 8 and 9 on SNJ54123J are designated No Connect (NC) and are not bonded internally. These pins must remain unconnected in the PCB layout; tying them to V_CC, GND, or any signal violates the device specification and may cause unpredictable behavior or increased leakage current. Refer to TI's SDLS043 datasheet Figure 1 for confirmed pin mapping.