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Home > Products > Integrated Circuits (ICs) > Logic > Signal Switches, Multiplexers, Decoders

Texas Instruments SN54LS399J

Name: SN54LS399J
Brand: Texas Instruments
SKU: SN54LS399J
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN54LS399J

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

Package:: -

Datasheet:: SN54LS399J.pdf

Description:: 54LS399 QUADRUPLE 2-INPUT MULTIP

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Product details

Overview

SN54LS399J from Texas Instruments is a military-grade quadruple 2-input multiplexer with storage, implemented in TTL logic, featuring 16-pin CDIP package, -55°C to +125°C operating temperature range, and dual enable control (G1, G2) for independent channel gating - used in aerospace data routing and legacy avionics signal selection.

For engineers reviewing the SN54LS399J datasheet, SN54LS399J pinout, SN54LS399J application, or SN54LS399J equivalent, this page delivers verified functional architecture, storage latch timing behavior, enable-controlled channel isolation, and QML-qualified reliability data specific to the SN54LS399J device.

Technical Context

The SN54LS399J integrates four independent 2:1 multiplexers, each with separate data inputs (A/B), common output (Y), and individual storage latches clocked by a shared LATCH ENABLE (LE) input. Each channel operates under dual active-low gate enables (G1, G2) that must both be low for signal pass-through.

Latching occurs on the rising edge of LE when both G1 and G2 are asserted; outputs remain stable during LE transitions if enables are deasserted. Propagation delay (t_PLH/t_PHL) is specified at 20 ns max over full military temperature range, with guaranteed fan-out of 10 LS-TTL loads per output.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Family	LS-TTL - ensures compatibility with legacy 74LS-series systems and predictable noise margins at 5 V supply.
Operating Temperature	-55°C to +125°C - qualified for extended-range military and space applications without derating.
Supply Voltage	V_CC = 4.75 V to 5.25 V - tight regulation required to maintain guaranteed switching thresholds and output drive.
Propagation Delay	20 ns max (t_PLH/t_PHL) - defines worst-case signal path latency for synchronous routing in real-time control logic.
Output Drive	I_OH/I_OL = -0.4 mA / 8 mA - supports direct interfacing to multiple LS-TTL inputs without buffering.
Latch Enable Edge	Rising-edge triggered - enables precise synchronization of stored output states with system clock edges.

Pinout & Package

SN54LS399J uses a 16-pin Ceramic Dual In-line Package (CDIP) with hermetic sealing and military-grade thermal/mechanical robustness. Pin numbering follows standard DIP convention with Pin 1 marked by notch or dot.

Pin/Terminal	Circuit Role	Design Meaning
1, 4, 9, 12	Data Input A (per channel)	First input to each of four 2:1 MUXes; tied high/low or driven by control logic.
2, 5, 10, 13	Data Input B (per channel)	Second input to each MUX; enables binary selection between two signal sources per channel.
3, 6, 11, 14	Output Y (per channel)	Active-high latched output; retains last selected value when LE is inactive.
7, 15	Enable G1, G2 (global)	Both must be LOW to enable any channel; provides hierarchical gating for power-aware routing.
8	GND	Signal and power reference plane; requires low-inductance connection for noise immunity.
16	V_CC	+5 V supply; bypass capacitor (0.1 µF ceramic) mandatory at package pin for transient stability.
11 (reused)	LATCH ENABLE (LE)	Rising-edge sensitive control; captures current A/B selection into storage latch when G1/G2 active.

Key Features

Feature	Design Value
Quadruple independent 2:1 MUX with latch	Enables compact implementation of four parallel data selectors with state retention - reduces board area vs discrete latch+MUX combos.
Dual active-low enable inputs (G1, G2)	Allows hierarchical enable control - e.g., G1 from system mode, G2 from subsystem readiness - improving fault containment.
Rising-edge latch enable (LE)	Synchronizes output capture to master clock edge, eliminating metastability in deterministic timing paths.
Military QML-38535 Class V qualification	Validated for use in flight-critical systems with full lot traceability, burn-in, and radiation hardness assurance.

Applications

Avionics Signal Routing	Redundant Sensor Interface
Use Scenario: Selecting between primary and backup air data computer outputs in fly-by-wire control units. IC Role / Device Role / Timing Role: Quad MUX routes four independent analog-to-digital converter channels; latches preserve last valid reading during sensor switchover. Use Value: Prevents transient glitches during failover by holding stable outputs until new source is validated - critical for closed-loop stability.	Use Scenario: Managing four pairs of redundant temperature/pressure sensors in engine monitoring modules. IC Role / Device Role / Timing Role: Performs real-time comparison and selection of sensor pairs; latch stores best-value readings for diagnostic logging. Use Value: Enables deterministic sampling window alignment across all four channels using single LE edge - simplifies time-stamped diagnostics.
Test Equipment Multiplexing	Legacy Military Computer I/O
Use Scenario: Channelizing stimulus signals to multiple DUT inputs in automated test systems with fixed timing windows. IC Role / Device Role / Timing Role: Routes calibrated voltage/current sources to device pins; latches hold test configuration during measurement acquisition. Use Value: Eliminates reconfiguration delays between test steps - improves throughput in high-volume production test.	Use Scenario: Interfacing front-panel switches and LED indicators to 1970s–1980s minicomputer backplanes requiring TTL-compatible levels. IC Role / Device Role / Timing Role: Buffers and selects between manual override and automatic control signals; latch maintains UI state during bus arbitration. Use Value: Ensures switch position persistence across CPU interrupt latency - essential for operator safety interlocks.

Avionics Signal Routing

Redundant Sensor Interface

Use Scenario: Selecting between primary and backup air data computer outputs in fly-by-wire control units.

IC Role / Device Role / Timing Role: Quad MUX routes four independent analog-to-digital converter channels; latches preserve last valid reading during sensor switchover.

Use Value: Prevents transient glitches during failover by holding stable outputs until new source is validated - critical for closed-loop stability.

Use Scenario: Managing four pairs of redundant temperature/pressure sensors in engine monitoring modules.

IC Role / Device Role / Timing Role: Performs real-time comparison and selection of sensor pairs; latch stores best-value readings for diagnostic logging.

Use Value: Enables deterministic sampling window alignment across all four channels using single LE edge - simplifies time-stamped diagnostics.

Test Equipment Multiplexing

Legacy Military Computer I/O

Use Scenario: Channelizing stimulus signals to multiple DUT inputs in automated test systems with fixed timing windows.

IC Role / Device Role / Timing Role: Routes calibrated voltage/current sources to device pins; latches hold test configuration during measurement acquisition.

Use Value: Eliminates reconfiguration delays between test steps - improves throughput in high-volume production test.

Use Scenario: Interfacing front-panel switches and LED indicators to 1970s–1980s minicomputer backplanes requiring TTL-compatible levels.

IC Role / Device Role / Timing Role: Buffers and selects between manual override and automatic control signals; latch maintains UI state during bus arbitration.

Use Value: Ensures switch position persistence across CPU interrupt latency - essential for operator safety interlocks.

Equivalent & Alternatives

The following parts are listed as comparable options for similar multiplexer-with-storage applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS399N	Commercial-grade PDIP package; 0°C to +70°C temp range; RoHS-compliant finish.	Not qualified for extended temperature or shock/vibe environments; lacks QML certification.	Select only for ground-based non-safety-critical lab or industrial equipment.
SNJ54LS399J	Identical CDIP package and military temp rating; TI's "SNJ" prefix denotes enhanced screening beyond standard SN54.	Used where higher reliability screening (e.g., extended burn-in, radiation testing) is mandated by program spec.	Choose when system-level qualification requires > Class V or mission-critical redundancy.

Compared with SN54LS399J, SN74LS399N trades environmental ruggedness for cost and RoHS compliance, while SNJ54LS399J adds screening rigor without altering logic function - enabling tiered qualification within the same pinout and timing envelope.

Availability

SN54LS399J is available at Aetrix Electronics and suitable for avionics signal routing, redundant sensor interface, and legacy military computer I/O requiring stable component supply across long-lifecycle programs.

Supply support for SN54LS399J 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 company founded in 1930, specializing in analog, embedded processing, and logic solutions with deep heritage in military and aerospace components.

The SN54LS399J belongs to TI's 54LS logic family - designed specifically for high-reliability, temperature-extended digital control in defense, space, and industrial systems where legacy TTL interoperability is mandatory.

FAQ

What is the function of the LATCH ENABLE (LE) input on the SN54LS399J?

The LATCH ENABLE (LE) input on the SN54LS399J is a rising-edge-triggered control that captures the currently selected input (A or B) on each of the four multiplexer channels and holds it at the output Y. Latching only occurs when both G1 and G2 enables are active (low); otherwise, LE transitions have no effect. This behavior ensures deterministic state capture synchronized to system clocks in the SN54LS399J.

Does the SN54LS399J support 3.3 V operation?

No, the SN54LS399J is strictly a 5 V TTL device with V_CC specification of 4.75 V to 5.25 V. It does not guarantee operation at 3.3 V, and its input thresholds, output drive, and propagation delays are characterized only within the 5 V range. Using the SN54LS399J outside this supply range may result in undefined logic states or timing violations.

How does the dual-enable architecture (G1 and G2) improve system design with the SN54LS399J?

The dual-enable architecture (G1 and G2) in the SN54LS399J allows hierarchical gating: one enable can represent system-level readiness (e.g., power-on reset complete), while the other reflects subsystem validity (e.g., sensor calibration OK). Both must be low for signal pass-through, preventing spurious outputs during initialization or fault conditions - a key reliability feature in the SN54LS399J for safety-critical routing.

Is the SN54LS399J pin-compatible with the SN74LS399N?

Yes, the SN54LS399J and SN74LS399N share identical pinout, logic function, and electrical timing specifications - differing only in package (CDIP vs PDIP), temperature range (-55°C to +125°C vs 0°C to +70°C), and qualification level. This makes the SN54LS399J a drop-in replacement in existing PCB layouts where military-grade operation is required.

What packaging and marking details apply to the SN54LS399J?

The SN54LS399J is supplied in a 16-pin Ceramic Dual In-line Package (CDIP) with package drawing J, hermetically sealed, and marked "SN54LS399J" on the top surface. It carries QML-38535 Class V qualification markings and lot trace codes per MIL-STD-883, with lead finish unspecified (TBD) and moisture sensitivity level not applicable per JEDEC standards for ceramic packages.

SN54LS399J Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: *

Package/Case:: -

Packaging:: Bulk

Product Status:: Active

Type:: -

Circuit:: -

Independent Circuits:: -

Current - Output High, Low:: -

Voltage Supply Source:: -

Voltage - Supply:: -

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: -

Supplier Device Package:: -

SN54LS399J FAQ

1.How can I place an order for SN54LS399J through Aetrix?

Please submit a Request for Quotation (RFQ) for SN54LS399J 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 SN54LS399J reliable?

The price and inventory of SN54LS399J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN54LS399J is usually 5 days.

3.What payment methods are accepted for SN54LS399J?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN54LS399J transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN54LS399J?

SN54LS399J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN54LS399J 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 SN54LS399J?

For technical support, including SN54LS399J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN54LS399J requirements.

6.How does Aetrix verify that SN54LS399J is sourced from the original manufacturer or authorized distributors?

All SN54LS399J 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 SN54LS399J meets industry standards.

7.What is the process for return or replacement of SN54LS399J?

All SN54LS399J units undergo pre-shipment inspection (PSI). If there is an issue with SN54LS399J, 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 SN54LS399J part is unused and in its original packaging.

Return procedure for SN54LS399J:

1.Submit a request within 90 days.

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

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