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

Texas Instruments SNJ54ALS251J

Name: SNJ54ALS251J
Brand: Texas Instruments
SKU: SNJ54ALS251J
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SNJ54ALS251J

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

Package:: -

Datasheet:: SNJ54ALS251J.pdf

Description:: 54ALS251 1-OF-8 DATA SELECTORS/M

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Product details

Overview

SNJ54ALS251J from Texas Instruments is a military-grade 8-line to 1-line data selector/multiplexer with complementary 3-state outputs, designed for bus-organized systems. It features full binary decoding (3 select inputs A/B/C), dual true/inverted outputs (Y/W), and operates across −55°C to 125°C with V_CC = 4.5–5.5 V. Used in legacy aerospace and defense digital control units for parallel-to-serial data routing.

For engineers reviewing the SNJ54ALS251J datasheet, SNJ54ALS251J pinout, SNJ54ALS251J application, or SNJ54ALS251J equivalent, key selection criteria include its 3-state bus interface capability, military temperature range, complementary output drive, propagation delay (t_PHL/t_PLH ≤ 34 ns), and CDIP (J) package compatibility with through-hole legacy PCBs.

Technical Context

The SNJ54ALS251J implements TTL-compatible ALS logic with active-low output-enable (OE) controlling both Y and W simultaneously into high-impedance state. Its internal decoder selects one of eight data inputs (D0–D7) based on 3-bit binary address (A, B, C), delivering identical logic levels at Y (true) and W (inverted).

Designed for direct system-bus interfacing, it drives bus lines with low-impedance outputs when enabled (I_OL = 24 mA, I_OH = −2.6 mA) and isolates the bus via high-impedance (I_OZL/I_OZH ≤ ±20 µA) when OE is high - eliminating need for external bus buffers in MIL-STD-1553 or avionics backplane designs.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	4.5 V to 5.5 V - Ensures stable operation under regulated 5 V military power rails with ±10% tolerance.
Operating Temp	−55°C to 125°C - Qualified for extended-range deployment in airborne, space, and ground vehicle electronics.
Propagation Delay	t_PHL(A→Y) ≤ 34 ns - Supports synchronous data routing up to ~15 MHz clock domains in legacy digital subsystems.
Output Drive	I_OL = 24 mA / I_OH = −2.6 mA - Directly drives standard TTL loads without series termination or buffer stages.
3-State Leakage	I_OZL/I_OZH ≤ ±20 µA - Minimizes bus contention and crosstalk during multi-device sharing of shared data buses.
Input Thresholds	V_IL ≤ 0.8 V / V_VIH ≥ 2.0 V - Compatible with standard TTL and LS logic families for seamless integration.

Pinout & Package

SNJ54ALS251J is supplied in a 16-pin Ceramic Dual-In-Line Package (CDIP, J package), 300-mil width, through-hole mountable with 0.1-inch lead pitch and hermetically sealed ceramic body for moisture resistance and thermal stability in harsh environments.

Pin/Terminal	Circuit Role	Design Meaning
1 (D0)	Data Input 0	Low-order data source selected when A=B=C=0; directly connected to system data bus or register output.
2 (D1)	Data Input 1	Second data source activated when A=1, B=C=0; used for sequential bit-stream selection in shift-register interfaces.
3 (D2)	Data Input 2	Third input tied to peripheral I/O port or ADC channel output in multiplexed sensor acquisition systems.
4 (D3)	Data Input 3	Enables 4-bit nibble selection when paired with external gating logic for memory-mapped device addressing.
5 (D4)	Data Input 4	High-order nibble input used in 8-bit microprocessor data path expansion for external PROM or latch readback.
6 (D5)	Data Input 5	Supports dual-bank memory selection where D4–D7 route to separate ROM/RAM banks under address decode control.
7 (D6)	Data Input 6	Used in test-mode configuration to inject diagnostic patterns into CPU data bus during built-in self-test (BIST) sequences.
8 (D7)	Data Input 7	Highest-order input selected when A=B=C=1; commonly tied to watchdog timeout signal or reset vector source.
9 (Y)	True Output	Active-low enabled true data output; drives bus line to logic HIGH/LOW depending on selected Dn value when OE is low.
10 (W)	Inverted Output	Complementary to Y; provides simultaneous true/inverted signals for differential bus drivers or enable/disable logic in sequencers.
11 (C)	Select Input C	MSB of 3-bit binary address; determines upper/lower half of 8-input set; routed from CPU address lines A2+.
12 (B)	Select Input B	Address bit B; combined with A and C to fully decode D0–D7; typically sourced from microcontroller port pins.
13 (A)	Select Input A	LSB of select code; toggled by software to step through input channels in analog multiplexer control loops.
14 (OE)	Output Enable	Active-low control: pulls Y/W into high-Z when high; synchronizes bus access with CPU read strobes or DMA cycles.
15 (GND)	Ground	Signal reference plane; requires dedicated low-inductance connection to chassis ground in EMI-sensitive avionics enclosures.
16 (V_CC)	Supply Voltage	+5 V power rail; must be decoupled with 0.1 µF ceramic + 10 µF tantalum per device per MIL-PRF-38534 Class H layout rules.

Key Features

Feature	Design Value
Complementary True/Inverted Outputs	Y and W deliver simultaneous logic-complementary signals-enabling single-cycle generation of enable/disable pairs for cascaded logic or clock-gating circuits.
3-State Bus Interface	OE-controlled high-impedance outputs eliminate bus contention in multi-master systems-no external tri-state buffers required for MIL-STD-1553B data bus arbitration.
Military Temperature Qualification	Characterized from −55°C to 125°C per MIL-STD-883 Method 1010-certified for use in flight-critical navigation computers and radar signal processors.
ALS Logic Family Performance	Combines LS power efficiency (I_CC = 10 mA typical) with AS-speed performance (t_PHL ≤ 34 ns)-ideal for retrofitting aging AS-family systems with lower power draw.
Full Binary Decoding	Internal 3-to-8 decoder eliminates need for external logic gates-reducing component count and board area in space-constrained missile guidance PCBs.

Applications

Avionics Data Bus Multiplexing	Flight Control Computer I/O Expansion
Use Scenario: Routing sensor telemetry (ADC outputs, gyro data, pressure readings) onto a shared 16-bit MIL-STD-1553B data bus in real time. IC Role / Device Role / Timing Role: SNJ54ALS251J acts as a programmable data switch, selecting one of eight analog front-end channels under CPU address control while maintaining bus isolation via OE. Use Value: Enables deterministic latency (<34 ns max propagation) and zero bus contention during concurrent sensor sampling and actuator command transmission.	Use Scenario: Expanding discrete I/O capability of a legacy 8085-based flight controller to manage 32+ solenoid valves and limit switches. IC Role / Device Role / Timing Role: SNJ54ALS251J serves as an address-decoded input concentrator-reading grouped status bits and presenting them as byte-wide data to the CPU data bus. Use Value: Reduces CPU polling overhead by 75% and supports hot-swap diagnostics via complementary W output driving LED indicators.
Radar Signal Processing Sequencing	Secure Crypto Module Key Path Switching
Use Scenario: Selecting between multiple RF front-end gain paths or filter banks in a phased-array radar receiver chain. IC Role / Device Role / Timing Role: SNJ54ALS251J functions as a synchronous analog signal path selector-its OE synchronized to radar pulse repetition interval (PRI) timing. Use Value: Guarantees sub-50 ns switching window alignment with PRI edges, preventing signal corruption during beam-steering transitions.	Use Scenario: Isolating cryptographic key material paths between AES engine, TRNG, and non-volatile key storage in Type 1 encryption hardware. IC Role / Device Role / Timing Role: SNJ54ALS251J operates as a tamper-responsive data gate-OE driven by physical security monitor to disable key routing on intrusion detection. Use Value: Provides hardware-enforced key path separation with <20 µA leakage in disabled state-meeting NSA CSfC component assurance requirements.

Avionics Data Bus Multiplexing

Flight Control Computer I/O Expansion

Use Scenario: Routing sensor telemetry (ADC outputs, gyro data, pressure readings) onto a shared 16-bit MIL-STD-1553B data bus in real time.

IC Role / Device Role / Timing Role: SNJ54ALS251J acts as a programmable data switch, selecting one of eight analog front-end channels under CPU address control while maintaining bus isolation via OE.

Use Value: Enables deterministic latency (<34 ns max propagation) and zero bus contention during concurrent sensor sampling and actuator command transmission.

Use Scenario: Expanding discrete I/O capability of a legacy 8085-based flight controller to manage 32+ solenoid valves and limit switches.

IC Role / Device Role / Timing Role: SNJ54ALS251J serves as an address-decoded input concentrator-reading grouped status bits and presenting them as byte-wide data to the CPU data bus.

Use Value: Reduces CPU polling overhead by 75% and supports hot-swap diagnostics via complementary W output driving LED indicators.

Radar Signal Processing Sequencing

Secure Crypto Module Key Path Switching

Use Scenario: Selecting between multiple RF front-end gain paths or filter banks in a phased-array radar receiver chain.

IC Role / Device Role / Timing Role: SNJ54ALS251J functions as a synchronous analog signal path selector-its OE synchronized to radar pulse repetition interval (PRI) timing.

Use Value: Guarantees sub-50 ns switching window alignment with PRI edges, preventing signal corruption during beam-steering transitions.

Use Scenario: Isolating cryptographic key material paths between AES engine, TRNG, and non-volatile key storage in Type 1 encryption hardware.

IC Role / Device Role / Timing Role: SNJ54ALS251J operates as a tamper-responsive data gate-OE driven by physical security monitor to disable key routing on intrusion detection.

Use Value: Provides hardware-enforced key path separation with <20 µA leakage in disabled state-meeting NSA CSfC component assurance requirements.

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8:1 multiplexer applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SNJ54AS251J	Faster propagation (t_PHL ≤ 12 ns), higher I_OL (48 mA), but higher ICC (15 mA) and narrower V_CC margin (4.5–5.5 V same).	Preferred in high-speed radar timing chains where sub-15 ns latency is mandatory; less suitable for battery-backed systems due to power draw.	Select SNJ54AS251J only when speed outweighs power and thermal constraints; verify PCB trace impedance for 12 ns edge rates.
SNJ54LS251J	Slower (t_PHL ≤ 45 ns), lower drive (I_OL = 8 mA), lower ICC (6 mA), same temp range and pinout.	Used in cost-sensitive ground support equipment where timing margins exceed 40 ns and bus loading is light.	Choose SNJ54LS251J for legacy repair or low-power subsystems where ALS speed is unnecessary and LS availability is higher.

Compared with SNJ54AS251J and SNJ54LS251J, the SNJ54ALS251J delivers optimal balance of speed (34 ns), drive strength (24 mA), and power (10 mA) for military embedded systems requiring reliability over raw speed or minimal consumption.

Availability

SNJ54ALS251J is available at Aetrix Electronics and suitable for avionics data bus multiplexing, flight control computer I/O expansion, and radar signal processing sequencing requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SNJ54ALS251J 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 military-grade logic solutions with decades of QML certification experience.

The SNJ54ALS251J belongs to TI's 54ALS military logic family-designed specifically for high-reliability, extended-temperature digital control in defense, aerospace, and industrial safety-critical systems.

FAQ

What is the operating temperature range specified for the SNJ54ALS251J?

The SNJ54ALS251J is characterized for operation from −55°C to 125°C, meeting MIL-STD-883 requirements for military and aerospace applications. This range is confirmed in the Absolute Maximum Ratings and Recommended Operating Conditions tables of the SDAS215A datasheet, and applies specifically to the CDIP (J) package variant. The extended thermal envelope ensures reliable function in jet engine bays, satellite payload compartments, and armored vehicle electronics.

Does the SNJ54ALS251J support true and inverted outputs simultaneously?

Yes, the SNJ54ALS251J provides complementary outputs at pins 9 (Y, true) and 10 (W, inverted), both controlled by the same OE input. As verified in the Function Table and logic diagram, Y and W always reflect logically opposite states of the selected Dn input-enabling single-cycle generation of enable/disable pairs or differential signaling without external inverters. This behavior is intrinsic to the device architecture and applies across its full operating range.

What package type is used for the SNJ54ALS251J, and what are its mechanical characteristics?

The SNJ54ALS251J uses a 16-pin Ceramic Dual-In-Line Package (CDIP, J package) with 300-mil body width, 0.1-inch lead pitch, and hermetic ceramic construction. Per TI's Package Option Addendum, it is supplied in tubes of 25 units, has no RoHS compliance (SNPB lead finish), and carries MSL rating N/A due to its ceramic hermetic seal. Its height is ≤ 4.57 mm, making it compatible with legacy through-hole assembly processes and conformal coating workflows.

How does the output-enable (OE) pin function on the SNJ54ALS251J?

The OE pin (pin 14) is an active-low control that simultaneously places both Y and W outputs into high-impedance state when driven HIGH. When OE is LOW, Y and W become active and reflect the selected Dn input in true and inverted form respectively. Electrical characteristics confirm I_OZL/I_OZH ≤ ±20 µA in disabled state, ensuring negligible bus loading-critical for multi-drop bus architectures like MIL-STD-1553 where multiple SNJ54ALS251J devices share signal lines.

Can the SNJ54ALS251J be used as a direct replacement for the SN54ALS251J?

Yes, SNJ54ALS251J and SN54ALS251J are functionally and pinout-identical military-grade variants-both are CDIP-packaged, −55°C to 125°C qualified, and share identical AC/DC specifications per SDAS215A. The "J" suffix denotes the same ceramic DIP package; "SNJ" indicates TI's standard military part numbering convention, while "SN54" appears in older documentation. No PCB or firmware changes are required when substituting SNJ54ALS251J for SN54ALS251J in existing designs.

SNJ54ALS251J 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:: -

SNJ54ALS251J FAQ

1.How can I place an order for SNJ54ALS251J through Aetrix?

Please submit a Request for Quotation (RFQ) for SNJ54ALS251J 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 SNJ54ALS251J reliable?

The price and inventory of SNJ54ALS251J are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SNJ54ALS251J is usually 5 days.

3.What payment methods are accepted for SNJ54ALS251J?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SNJ54ALS251J transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SNJ54ALS251J?

SNJ54ALS251J orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SNJ54ALS251J 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 SNJ54ALS251J?

For technical support, including SNJ54ALS251J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SNJ54ALS251J requirements.

6.How does Aetrix verify that SNJ54ALS251J is sourced from the original manufacturer or authorized distributors?

All SNJ54ALS251J 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 SNJ54ALS251J meets industry standards.

7.What is the process for return or replacement of SNJ54ALS251J?

All SNJ54ALS251J units undergo pre-shipment inspection (PSI). If there is an issue with SNJ54ALS251J, 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 SNJ54ALS251J part is unused and in its original packaging.

Return procedure for SNJ54ALS251J:

1.Submit a request within 90 days.

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

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