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Texas Instruments SN74ALS139N
- Part No.:
- SN74ALS139N
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS139N.pdf
- Description:
- IC DECODER/DEMUX 1X2:4 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:406
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Product details
Overview
SN74ALS139N from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin PDIP package, designed for high-speed memory decoding and data routing. It features Schottky-clamped TTL logic, 0°C to 70°C operating range, 3–14 ns propagation delay (tPLH/tPHL), and fully buffered inputs with one normalized load per input.
For engineers reviewing the SN74ALS139N datasheet, SN74ALS139N pinout, SN74ALS139N application, or SN74ALS139N equivalent, this device supports fast-enable memory systems, cascaded decoding architectures, and demultiplexing where active-low enable doubles as a data line - critical for legacy industrial control and instrumentation bus interfaces.
Technical Context
The SN74ALS139N implements two independent decoders, each with active-low enable (1G/2G), two select inputs (A/B), and four active-low outputs (Y0–Y3). Its Schottky-clamped bipolar architecture delivers TTL-compatible voltage thresholds (VIH = 2 V, VIL = 0.8 V) and drive capability (IOL = 8 mA, IOH = –0.4 mA).
Propagation delays are symmetric across input-to-output paths (A/B→Y and G→Y), with tPLH/tPHL specified at 3–14 ns under CL = 50 pF, RL = 500 Ω. Input clamping diodes suppress ringing, and all outputs are totem-pole (non-open-collector), eliminating external pull-ups in standard logic interfacing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) TTL - enables higher speed than LS with lower power than standard TTL. |
| Propagation Delay | 3–14 ns (tPLH/tPHL) - ensures minimal added latency in memory address decode paths. |
| Supply Voltage | 4.5–5.5 V - compatible with standard 5 V TTL rails without regulation overhead. |
| Output Drive | IOL = 8 mA / IOH = –0.4 mA - sufficient to directly drive multiple TTL inputs or small capacitive loads. |
| Input Load | One normalized TTL load per input - simplifies fanout calculation and eliminates need for input buffering. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded systems and industrial control panels. |
| Package | 16-pin PDIP (N) - through-hole compatible for prototyping, legacy repair, and ruggedized PCBs. |
Pinout & Package
SN74ALS139N uses a 16-pin plastic dual in-line package (PDIP-N) with 0.3-inch width and standard DIP footprint. Pin 1 is marked by a notch or dot; pin numbering follows counterclockwise convention from top-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1G, 2G | Active-low enable inputs | Enable/disable respective decoder; double as data lines in demux mode - no external gating required. |
| 1A, 1B / 2A, 2B | Binary select inputs | Address bits for 2-to-4 decoding; fully buffered to minimize loading on upstream drivers. |
| 1Y0–1Y3 / 2Y0–2Y3 | Active-low decoded outputs | Assert low for selected output; totem-pole structure ensures defined logic levels without pull-ups. |
| VCC (Pin 16) | Positive supply | 5 V nominal; internal decoupling not required due to low ICC (8–13 mA typical). |
| GND (Pin 8) | Ground reference | Common return for all logic and output currents; shared ground plane recommended. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent decoders | Two complete 2:4 decode blocks in one IC - reduces board space vs. discrete 74ALS138 + gate solutions. |
| Schottky-clamped inputs | Clamping diodes suppress transmission-line ringing - improves signal integrity in backplane or long-trace applications. |
| Active-low enable as data line | Eliminates need for external AND gates in demux configurations - simplifies timing-critical data path design. |
| Normalized input loading | Each input presents exactly one TTL load - enables precise fanout planning without derating. |
| Low propagation skew | tPLH/tPHL match within 1 ns across A/B/G inputs - ensures deterministic timing in synchronous decode trees. |
Applications
| Memory Address Decoding | Bus Demultiplexing |
|---|---|
Use Scenario: Selecting one of four RAM/ROM chips in a 16-bit microprocessor system using A1–A2 address lines. IC Role / Device Role / Timing Role: Dual decoder maps 2-bit address to chip-select signals; active-low outputs directly assert /CS pins. Use Value: Propagation delay ≤14 ns ensures decode completes before memory access window closes - no wait-state insertion needed. | Use Scenario: Routing a single data stream from a microcontroller UART to one of four peripheral UART receivers. IC Role / Device Role / Timing Role: Acts as 1:4 data switch; enable pin driven by control register bit to select destination channel. Use Value: Enables zero-latency channel selection with no additional glue logic - supports real-time serial protocol switching. |
| Cascaded Decoder Tree | Legacy Industrial I/O Expansion |
Use Scenario: Building a 4-to-16 line decoder using two SN74ALS139N devices with hierarchical enable chaining. IC Role / Device Role / Timing Role: First-stage decoder selects second-stage enable; both stages use identical timing behavior. Use Value: Matched tPLH/tPHL across devices guarantees predictable worst-case decode latency - critical for deterministic PLC scan cycles. | Use Scenario: Expanding discrete I/O points on an older PLC rack using parallel control bus and status feedback. IC Role / Device Role / Timing Role: Translates 2-bit command codes into 4-channel enable signals for opto-isolated output drivers. Use Value: Schottky clamping prevents false triggering from EMI on long I/O cables - improves reliability in factory-floor environments. |
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 |
|---|---|---|---|
| SN74LS139N | Slower propagation (15–25 ns), higher ICC (19 mA), same pinout and logic function. | Acceptable where timing margin >10 ns exists; less suitable for high-speed memory systems. | Choose for cost-sensitive legacy designs where ALS speed is unnecessary. |
| SN74HC139N | CMOS technology, wider VCC range (2–6 V), lower ICC (<8 µA), but slower at 5 V (20–30 ns). | Requires level-shifting when interfacing with TTL buses; unsuitable for direct replacement in existing ALS/LS systems. | Prefer only in new low-power 5 V or mixed-voltage designs with adequate timing budget. |
Compared with SN74LS139N and SN74HC139N, the SN74ALS139N uniquely balances speed (≤14 ns), TTL compatibility, and power efficiency (8–13 mA ICC) - making it the optimal choice for upgrading legacy LS-based memory controllers without redesigning timing or interface circuitry.
Availability
SN74ALS139N is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment upgrades, and military-grade commercial electronics requiring stable component supply over extended production lifecycles.
Supply support for SN74ALS139N 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 products for industrial, automotive, and communications markets.
The SN74ALS139N belongs to TI's legacy Advanced Schottky TTL logic family, engineered specifically for high-speed memory decoding and data-routing systems where propagation delay and interface compatibility outweigh ultra-low power requirements.
FAQ
What is the maximum operating temperature range for the SN74ALS139N?
The SN74ALS139N is characterized for operation from 0°C to 70°C - the commercial temperature grade. This range is confirmed in the "recommended operating conditions" table of the SDAS204A datasheet and applies specifically to the SN74ALS139N variant, distinguishing it from the military-grade SN54ALS139 (–55°C to 125°C).
Does the SN74ALS139N support 3-state outputs?
No, the SN74ALS139N does not feature 3-state outputs. All eight outputs (1Y0–1Y3 and 2Y0–2Y3) are totem-pole, active-low, push-pull structures. The datasheet contains no mention of output enable/disable control beyond the active-low G inputs, and no electrical characteristics for high-impedance states are specified for SN74ALS139N.
Can the SN74ALS139N be used as a demultiplexer?
Yes, the SN74ALS139N can be used as a dual 1-to-4 demultiplexer. The active-low enable inputs (1G, 2G) serve as data inputs, while the select lines (A/B) determine which output is asserted low. This functionality is explicitly described in the device description and supported by the function table showing G as the primary enable/data control.
What is the supply current consumption of the SN74ALS139N under typical operation?
The SN74ALS139N draws 8–13 mA of supply current (ICC) at VCC = 5.5 V, as specified in the "electrical characteristics" table. This value represents total quiescent current for both decoders and is measured with all inputs static - no dynamic switching current is included, and actual consumption scales with toggle rate.
Is the SN74ALS139N pin-compatible with the SN74LS139N?
Yes, the SN74ALS139N is pin-compatible with the SN74LS139N. Both devices use identical 16-pin PDIP (N) packaging and share identical pin functions, pin numbering, and logic behavior - enabling direct drop-in replacement in existing LS-based designs where improved speed and reduced power are beneficial.
SN74ALS139N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 2:4
- Independent Circuits:
- 2
- Current - Output High, Low:
- 400µA, 8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
SN74ALS139N FAQ
1.How can I place an order for SN74ALS139N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS139N 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 SN74ALS139N reliable?
The price and inventory of SN74ALS139N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS139N is usually 5 days.
3.What payment methods are accepted for SN74ALS139N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS139N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS139N?
SN74ALS139N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS139N 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 SN74ALS139N?
For technical support, including SN74ALS139N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS139N requirements.
6.How does Aetrix verify that SN74ALS139N is sourced from the original manufacturer or authorized distributors?
All SN74ALS139N 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 SN74ALS139N meets industry standards.
7.What is the process for return or replacement of SN74ALS139N?
All SN74ALS139N units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS139N, 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 SN74ALS139N part is unused and in its original packaging.
Return procedure for SN74ALS139N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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