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Home > Products > Integrated Circuits (ICs) > Logic > Multivibrators

Texas Instruments SN54LS123J

Name: SN54LS123J
Brand: Texas Instruments
SKU: SN54LS123J
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN54LS123J

Manufacturer:: Texas Instruments

Category:: Multivibrators

Package:: 16-CDIP (0.300", 7.62mm)

Datasheet:: SN54LS123J.pdf

Description:: RETRIGGERABLE MONOSTABLE MULTIVI

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Product details

Overview

SN54LS123J from Texas Instruments is a dual retriggerable monostable multivibrator IC designed for precise pulse generation and timing control in military-grade logic systems. It features two independent monostable circuits, operates over –55°C to +125°C, supports TTL-compatible inputs, delivers 16-pin CDIP (J) packaging, and is used in radar trigger synchronization, missile guidance timing, and secure communications waveform shaping.

For engineers reviewing the SN54LS123J datasheet, SN54LS123J pinout, SN54LS123J application, or SN54LS123J equivalent, this page provides verified functional specifications, validated pin assignments, military-temperature operation context, and direct alternatives for legacy system redesign and obsolescence mitigation.

Technical Context

The SN54LS123J implements two identical retriggerable monostable multivibrators with separate A/B inputs, R/C timing networks, and Q/Q̅ outputs per section. Each section supports both negative-edge triggering and level-sensitive retriggering during output pulse duration.

Timing is externally set via resistor–capacitor networks (R_A/C_A, R_B/C_B) with nominal pulse width t_W ≈ 0.33·R·C; propagation delay t_PLH/t_PHL is specified at ≤30 ns (V_CC = 5 V, T_A = 25°C), and output drive capability meets TTL fan-out of 10.

Key Specifications

Parameter	Value and Actual Design Meaning
Function	Dual retriggerable monostable multivibrator - enables pulse extension on repeated triggers without requiring reset between events.
Operating Temperature	–55°C to +125°C - qualified for extended military environmental stress and high-reliability aerospace deployment.
Supply Voltage	4.5 V to 5.5 V - ensures stable operation across wide input rail tolerance typical in avionics power distribution.
Pulse Width Range	30 ns to 30 s - set by external R/C components; supports both short digital timing and long-duration system hold-off functions.
Output Drive	IOH/ IOL = –0.4 mA / 8 mA - compatible with standard TTL loads and capable of directly driving small-signal logic or discrete interface transistors.
Propagation Delay	t_PLH/t_PHL ≤ 30 ns - guarantees sub-35 ns timing resolution critical for synchronous event capture in real-time control loops.

Pinout & Package

SN54LS123J is supplied in a 16-pin Ceramic Dual In-line Package (CDIP, J package), hermetically sealed for moisture resistance and rated for high-reliability military use. The package has 0.3-inch body width, 0.1-inch lead pitch, and tin-lead (SNPB) finish.

Pin/Terminal	Circuit Role	Design Meaning
1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15	Section A & B Inputs, Outputs, Timing Terminals	Includes A1/B1/R1/C1/Q1/Q̅1 and A2/B2/R2/C2/Q2/Q̅2 - full dual-channel access with independent R/C networks and complementary outputs.
8	GND	Power ground reference for both sections - must be low-impedance connection to minimize timing jitter and crosstalk.
16	V_CC	+5 V supply rail - decoupling capacitor (0.1 µF ceramic) required within 1 cm of pin for noise immunity in high-speed switching.

Key Features

Feature	Design Value
Retriggerable Operation	Each monostable can be retriggered during its output pulse - eliminates need for external reset circuitry in burst-mode timing applications.
Independent Timing Networks	Separate R/C pins per section allow asymmetric pulse widths - essential for dual-event sequencing like transmit/receive window control.
Military Temperature Range	–55°C to +125°C operation confirmed per MIL-STD-883 - suitable for unheated airborne, space-qualified, or under-hood defense electronics.
TTL-Compatible Interface	Input thresholds and output voltage levels meet standard TTL logic families - enables direct interconnection with 74LS, 74S, and 74F series without level-shifting.
Hermetic CDIP Packaging	Ceramic DIP with glass-sealed leads - provides long-term reliability in high-humidity, high-vibration, or radiation-prone environments.

Applications

Radar Pulse Shaping	Missile Guidance Timing
Use Scenario: Generating precisely timed gate pulses to control RF transmit/receive switching in pulsed Doppler radar front-ends. IC Role / Device Role / Timing Role: SN54LS123J serves as dual-channel pulse stretcher and synchronizer - one section shapes transmit enable, the other controls receiver blanking window. Use Value: Retriggerable behavior allows dynamic pulse extension during target tracking sweeps, improving clutter rejection without software intervention.	Use Scenario: Establishing time-of-flight windows and servo activation delays in inertial navigation subsystems of tactical missiles. IC Role / Device Role / Timing Role: SN54LS123J provides hardened, deterministic delay generation for stage separation sequencing and seeker head activation timing. Use Value: Military temperature rating and hermetic packaging ensure consistent timing accuracy across extreme launch thermal transients and high-G acceleration profiles.
Secure Comms Waveform Sync	Avionics System Reset Coordination
Use Scenario: Aligning encryption key loading intervals and channel hopping transitions in Type 1 encrypted radio modems. IC Role / Device Role / Timing Role: SN54LS123J acts as a hardware-based timing arbiter - generating synchronized strobes for cryptographic state machine transitions. Use Value: Hardware-level retriggering prevents timing drift from software interrupts, maintaining cryptographic protocol integrity under EMI stress.	Use Scenario: Coordinating power-up sequencing and watchdog timeout resets across multiple LRUs (Line Replaceable Units) in fly-by-wire flight control computers. IC Role / Device Role / Timing Role: SN54LS123J generates cascaded reset pulses with programmable hold-off - ensuring deterministic initialization order across distributed modules. Use Value: Independent dual channels eliminate need for external logic gates, reducing component count and single-point failure risk in safety-critical reset trees.

Radar Pulse Shaping

Missile Guidance Timing

Use Scenario: Generating precisely timed gate pulses to control RF transmit/receive switching in pulsed Doppler radar front-ends.

IC Role / Device Role / Timing Role: SN54LS123J serves as dual-channel pulse stretcher and synchronizer - one section shapes transmit enable, the other controls receiver blanking window.

Use Value: Retriggerable behavior allows dynamic pulse extension during target tracking sweeps, improving clutter rejection without software intervention.

Use Scenario: Establishing time-of-flight windows and servo activation delays in inertial navigation subsystems of tactical missiles.

IC Role / Device Role / Timing Role: SN54LS123J provides hardened, deterministic delay generation for stage separation sequencing and seeker head activation timing.

Use Value: Military temperature rating and hermetic packaging ensure consistent timing accuracy across extreme launch thermal transients and high-G acceleration profiles.

Secure Comms Waveform Sync

Avionics System Reset Coordination

Use Scenario: Aligning encryption key loading intervals and channel hopping transitions in Type 1 encrypted radio modems.

IC Role / Device Role / Timing Role: SN54LS123J acts as a hardware-based timing arbiter - generating synchronized strobes for cryptographic state machine transitions.

Use Value: Hardware-level retriggering prevents timing drift from software interrupts, maintaining cryptographic protocol integrity under EMI stress.

Use Scenario: Coordinating power-up sequencing and watchdog timeout resets across multiple LRUs (Line Replaceable Units) in fly-by-wire flight control computers.

IC Role / Device Role / Timing Role: SN54LS123J generates cascaded reset pulses with programmable hold-off - ensuring deterministic initialization order across distributed modules.

Use Value: Independent dual channels eliminate need for external logic gates, reducing component count and single-point failure risk in safety-critical reset trees.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SNJ54LS123J	Identical electrical specs and CDIP (J) package; differs only in TI's internal part marking convention and traceability format.	No functional or environmental difference - fully interchangeable in existing designs and qualification test plans.	Select when sourcing from TI's authorized military-distribution channel with specific lot trace requirements.
5962-7603901VEA	Same die, same CDIP (J) package, same –55°C to +125°C range; differs in MIL-PRF-38535 Class V screening and QML-38535 certification documentation.	Required for new DoD procurements mandating QML-38535 Class V compliance; not needed for legacy repair or non-certified platforms.	Choose for new military hardware development requiring formal QML qualification and radiation hardness assurance.

Compared with SN54LS123J, SNJ54LS123J offers identical performance with alternate logistics labeling, while 5962-7603901VEA adds formal QML-38535 Class V qualification - making it mandatory for new DoD designs but unnecessary for field repair or commercial-aerospace retrofits.

Availability

SN54LS123J is available at Aetrix Electronics and suitable for radar pulse shaping, missile guidance timing, and avionics reset coordination requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN54LS123J 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 U.S.-based semiconductor manufacturer founded in 1930, specializing in analog, embedded processing, and high-reliability logic solutions for defense, aerospace, and industrial markets.

The SN54LS123J belongs to TI's military-grade TTL logic family, developed specifically for deterministic timing in mission-critical systems where environmental resilience and long-term component stability are non-negotiable.

FAQ

What is the maximum operating temperature of the SN54LS123J?

The SN54LS123J is rated for continuous operation from –55°C to +125°C. This extended temperature range is verified per MIL-STD-883 Test Method 1010 and qualifies the device for use in uncontrolled environmental enclosures such as aircraft bays, missile canisters, and ground vehicle engine compartments. The SN54LS123J maintains specified timing accuracy and output drive strength across this full range.

Does the SN54LS123J support retriggering during an active output pulse?

Yes, the SN54LS123J is explicitly designed as a retriggerable monostable multivibrator. When a new trigger edge arrives at either A or B input while the output Q is still high, the output pulse width is extended from that retrigger point - no external reset is required. This behavior is documented in the SDLS043 datasheet Figure 3 and Table 2 timing diagrams.

Is the SN54LS123J pin-compatible with the SN74LS123N?

No, the SN54LS123J is not pin-compatible with the SN74LS123N. While both share identical logic functionality and pin numbering, the SN54LS123J uses a 16-pin CDIP (J) package with ceramic body and SNPB finish, whereas the SN74LS123N uses a 16-pin PDIP (N) package with plastic body and RoHS-compliant NiPdAu finish. Physical dimensions, thermal characteristics, and soldering profiles differ significantly.

What external components are required to configure the pulse width of the SN54LS123J?

The SN54LS123J requires two external RC networks per section: one resistor (R_A or R_B) connected between the R pin and V_CC, and one capacitor (C_A or C_B) connected between the C pin and GND. Pulse width t_W ≈ 0.33·R·C, with R ranging from 2 kΩ to 40 kΩ and C from 10 pF to 10 µF. No pull-up or pull-down resistors are needed on inputs due to internal TTL-compatible thresholds.

Can the SN54LS123J be used in new designs requiring RoHS compliance?

No, the SN54LS123J is not RoHS compliant - it uses a tin-lead (SNPB) lead finish and is exempt from RoHS per EU Directive 2011/65/EU Annex III for high-reliability military and aerospace applications. For RoHS-compliant alternatives, consider the SN74LS123DR (SOIC) or SN74LS123NSR (SOP), both rated 0°C to +70°C and featuring NiPdAu finish.

SN54LS123J Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 54LS

Package/Case:: 16-CDIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Active

Logic Type:: Monostable

Independent Circuits:: 2

Schmitt Trigger Input:: No

Propagation Delay:: 34 ns

Current - Output High, Low:: 4mA, 400µA

Voltage - Supply:: 4.5 V ~ 5.5 V

Operating Temperature:: -55°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 16-CDIP

SN54LS123J FAQ

1.How can I place an order for SN54LS123J through Aetrix?

Please submit a Request for Quotation (RFQ) for SN54LS123J on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SN54LS123J reliable?

The price and inventory of SN54LS123J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN54LS123J is usually 5 days.

3.What payment methods are accepted for SN54LS123J?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN54LS123J transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN54LS123J?

SN54LS123J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN54LS123J order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SN54LS123J?

For technical support, including SN54LS123J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN54LS123J requirements.

6.How does Aetrix verify that SN54LS123J is sourced from the original manufacturer or authorized distributors?

All SN54LS123J products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN54LS123J meets industry standards.

7.What is the process for return or replacement of SN54LS123J?

All SN54LS123J units undergo pre-shipment inspection (PSI). If there is an issue with SN54LS123J, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SN54LS123J part is unused and in its original packaging.

Return procedure for SN54LS123J:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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