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Texas Instruments SNJ54ALS139J
- Part No.:
- SNJ54ALS139J
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- -
- Datasheet:
-
SNJ54ALS139J.pdf
- Description:
- 54ALS139 DUAL 2-LINE TO 4-LINE D
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Product details
Overview
SNJ54ALS139J from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer designed for high-speed memory decoding and data-routing systems. It features Schottky-clamped TTL logic, operates across –55°C to 125°C, delivers propagation delays as low as 3 ns (tPLH/tPHL), supports 8 mA low-level output drive, and uses active-low enable inputs for cascading. It is deployed in military-grade memory subsystems where minimal system decoding delay is critical.
For engineers reviewing the SNJ54ALS139J datasheet, SNJ54ALS139J pinout, SNJ54ALS139J application, or SNJ54ALS139J equivalent, this page provides verified functional specifications, military-temperature-rated performance data, J-package pin mapping, real-world use cases in memory and data-path systems, and two validated alternative part numbers with documented technical distinctions.
Technical Context
The SNJ54ALS139J integrates two independent decoders, each with fully buffered inputs presenting only one normalized load and Schottky-clamped inputs to suppress line ringing. Its dual active-low enable (1G, 2G) allows synchronous gating of both decoder sections or use as demultiplexing data lines.
It implements positive-logic decoding with active-low outputs (Y0–Y3 per section), accepts standard TTL input thresholds (VIL ≤ 0.8 V, VIH ≥ 2 V), and drives loads directly with totem-pole outputs-no open-collector configuration. All timing parameters are specified over the full –55°C to 125°C military temperature range at VCC = 4.5 V to 5.5 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) TTL - enables higher speed than LS while maintaining compatibility and lower power than standard Schottky. |
| Propagation Delay | 3 ns min / 17 ns max (A/B or G → Y) - ensures sub-20 ns worst-case path delay in memory address decode trees. |
| Output Drive | 8 mA sink capability (IOL) - sufficient to drive multiple TTL inputs or small capacitive bus loads without buffering. |
| Operating Temperature | –55°C to 125°C - qualified for extended military and aerospace applications requiring environmental robustness. |
| Supply Voltage Range | 4.5 V to 5.5 V - compatible with regulated 5 V systems and tolerant of rail variation in ruggedized platforms. |
| Input Load | One normalized TTL load per input - simplifies fanout planning and eliminates need for input current budgeting beyond standard TTL rules. |
| Enable Architecture | Dual independent active-low enables (1G, 2G) - permits selective activation of either decoder or coordinated gating for hierarchical decoding. |
Pinout & Package
Ceramic Dual-In-Line Package (CDIP), 16-pin, 300-mil width, hermetically sealed, lead finish: SNPB (tin-lead), RoHS non-compliant, MSL not applicable.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | 1B (Select B) | Second address input for Decoder 1; referenced to GND/VCC for binary selection (00–11). |
| 2 | 1A (Select A) | First address input for Decoder 1; paired with 1B to select one of four outputs (Y0–Y3). |
| 3 | 1G (Enable) | Active-low chip enable for Decoder 1; when high, all Y outputs forced high (disabled state). |
| 4 | 1Y0 | Active-low decoded output 0 for Decoder 1; asserted low when 1G=L, 1B=0, 1A=0. |
| 5 | 1Y1 | Active-low decoded output 1 for Decoder 1; asserted low when 1G=L, 1B=0, 1A=1. |
| 6 | 1Y2 | Active-low decoded output 2 for Decoder 1; asserted low when 1G=L, 1B=1, 1A=0. |
| 7 | 1Y3 | Active-low decoded output 3 for Decoder 1; asserted low when 1G=L, 1B=1, 1A=1. |
| 8 | GND | Ground reference for logic and power return; must be low-impedance connection in high-speed layouts. |
| 9 | 2Y3 | Active-low decoded output 3 for Decoder 2; independent of Decoder 1 outputs and controls. |
| 10 | 2Y2 | Active-low decoded output 2 for Decoder 2; shares no internal nodes with Decoder 1 section. |
| 11 | 2Y1 | Active-low decoded output 1 for Decoder 2; fully isolated timing and loading behavior from Decoder 1. |
| 12 | 2Y0 | Active-low decoded output 0 for Decoder 2; enables parallel decoding of two independent 2-bit fields. |
| 13 | 2B | Second address input for Decoder 2; electrically isolated but pin-compatible with 1B for layout symmetry. |
| 14 | 2A | First address input for Decoder 2; matches 1A function and timing spec, allowing identical routing. |
| 15 | 2G | Active-low enable for Decoder 2; permits independent or synchronized control with 1G via external logic. |
| 16 | VCC | +5 V supply input; requires local 0.1 µF ceramic bypass capacitor placed within 5 mm of pin per MIL-STD-883. |
Key Features
| Feature | Design Value |
|---|---|
| Schottky-clamped inputs | Suppresses transmission-line ringing on long PCB traces or backplanes, eliminating need for external termination in most memory bus implementations. |
| Dual independent enables (1G/2G) | Enables hierarchical decoding (e.g., bank select + row/column) without external AND gates, reducing component count and propagation latency. |
| 3 ns minimum propagation delay | Allows integration into sub-25 ns memory access cycles - critical for 16-bit minicomputer and military avionics address decode paths. |
| One normalized TTL input load | Permits direct fanout to up to 10 standard TTL inputs without buffer stages, simplifying address distribution networks. |
| Military temperature qualification | Validated operation from –55°C to 125°C per MIL-PRF-38535, supporting deployment in unheated airborne or space-qualified systems. |
Applications
| Memory Address Decoding | Data Path Demultiplexing |
|---|---|
|
Use Scenario: Selecting one of four memory banks in a 16-bit military computer using two high-order address bits and a bank-enable signal. IC Role / Device Role / Timing Role: SNJ54ALS139J acts as a bank-select decoder, asserting active-low chip-select lines with ≤17 ns worst-case delay to meet tight 45 ns memory cycle timing. Use Value: Eliminates added gate delay from discrete logic, preserving margin in legacy TTL-based memory subsystems operating at maximum rated speed. |
Use Scenario: Routing a single data stream from a shared bus to one of four test instrumentation channels under microcontroller control. IC Role / Device Role / Timing Role: SNJ54ALS139J functions as a synchronous 1:4 demultiplexer, using 1G/2G as channel-enable strobes synchronized to system clock edges. Use Value: Provides deterministic, glitch-free channel selection with no hold-time violations, even when input select lines change near clock transitions. |
| Priority Interrupt Encoding | Legacy System Bus Expansion |
|
Use Scenario: Encoding four asynchronous interrupt request lines (IRQ0–IRQ3) into a 2-bit priority-encoded vector for an 8086-based controller. IC Role / Device Role / Timing Role: SNJ54ALS139J serves as a fixed-priority encoder by wiring IRQ lines to enables and tying selects to fixed logic levels. Use Value: Delivers deterministic 3–17 ns response latency - faster than software polling - while requiring zero firmware overhead or CPU cycles. |
Use Scenario: Expanding a 16-bit ISA-compatible backplane to support eight peripheral slots using two-level address decoding. IC Role / Device Role / Timing Role: SNJ54ALS139J implements second-stage slot decoding, driven by upper address bits and board-select signals. Use Value: Maintains strict timing alignment with ISA specification's 250 ns address setup/hold windows due to guaranteed sub-20 ns propagation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual 2-to-4 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SNJ54AS139J | AS family: 1.5 ns typical propagation delay, higher ICC (18 mA), tighter VIL/VOL specs, but reduced noise margin at temperature extremes. | Better suited for ultra-high-speed systems where <10 ns total decode path is mandatory; less tolerant of marginal VCC or EMI in field-deployed hardware. | Select SNJ54AS139J only if measured system timing closure requires <3 ns improvement and thermal environment is controlled. |
| SNJ54LS139J | LS family: 22 ns max propagation delay, 8 mA IOL, lower ICC (3 mA), wider industrial temp range (–55°C to 125°C retained), but no Schottky clamping. | Appropriate for cost-sensitive, lower-speed upgrades where board-level ringing is mitigated externally and timing budget exceeds 20 ns. | Choose SNJ54LS139J for legacy repair or inventory rationalization where speed penalty is acceptable and power reduction is prioritized. |
Compared with SNJ54ALS139J, SNJ54AS139J trades higher power and reduced noise immunity for measurable speed gain, while SNJ54LS139J sacrifices 30%+ propagation performance for lower static power and broader design margin in non-critical paths.
Availability
SNJ54ALS139J is available at Aetrix Electronics and suitable for military computing, avionics subsystems, and ruggedized industrial controllers requiring stable component supply across extended temperature ranges and long product lifecycles.
Supply support for SNJ54ALS139J 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 high-reliability logic solutions for defense, aerospace, and industrial markets.
The SNJ54ALS139J belongs to TI's military-qualified ALS logic family, engineered specifically for high-speed memory decoding and data-routing in systems where propagation delay, temperature resilience, and long-term obsolescence management are primary design constraints.
FAQ
What is the maximum operating temperature range for the SNJ54ALS139J?
The SNJ54ALS139J is characterized for continuous operation from –55°C to 125°C, meeting MIL-PRF-38535 Class B requirements. This full military temperature range is confirmed in the SDAS204A datasheet absolute maximum and recommended operating conditions tables, and applies specifically to the J-package variant.
Does the SNJ54ALS139J support 3-state outputs?
No, the SNJ54ALS139J does not feature 3-state outputs. It uses standard totem-pole TTL outputs with active-low logic levels (Y0–Y3 sink current when asserted). The datasheet logic diagram, function table, and electrical characteristics confirm only high/low output states - no high-impedance mode or output-enable control pins are present.
Can the SNJ54ALS139J be used as a demultiplexer?
Yes, the SNJ54ALS139J can be used as a demultiplexer: its active-low enable inputs (1G, 2G) serve as data inputs, while select lines (1A/1B, 2A/2B) route the asserted enable to one of four active-low outputs (1Y0–1Y3 or 2Y0–2Y3). This is explicitly stated in the device description and supported by the function table.
What is the typical propagation delay of the SNJ54ALS139J at 25°C?
The typical propagation delay of the SNJ54ALS139J is 7 ns for tPLH and tPHL (A/B or G → Y) at VCC = 5 V and TA = 25°C, as listed in the "electrical characteristics" table under "TYP‡" column. This value is derived from characterization data and applies to the J-package under nominal conditions.
Is the SNJ54ALS139J RoHS compliant?
No, the SNJ54ALS139J is not RoHS compliant. Per TI's Package Option Addendum, the J-package variant carries "No" in the RoHS column and uses SNPB (tin-lead) lead finish. This reflects its heritage as a military-specification part intended for applications exempt from RoHS directives.
SNJ54ALS139J 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:
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- Mounting Type:
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- Supplier Device Package:
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SNJ54ALS139J FAQ
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For technical support, including SNJ54ALS139J datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SNJ54ALS139J requirements.
6.How does Aetrix verify that SNJ54ALS139J is sourced from the original manufacturer or authorized distributors?
All SNJ54ALS139J 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 SNJ54ALS139J meets industry standards.
7.What is the process for return or replacement of SNJ54ALS139J?
All SNJ54ALS139J units undergo pre-shipment inspection (PSI). If there is an issue with SNJ54ALS139J, 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 SNJ54ALS139J part is unused and in its original packaging.
Return procedure for SNJ54ALS139J:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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