My Inquiry
My Account
Texas Instruments SN74ALS139D
- Part No.:
- SN74ALS139D
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74ALS139D.pdf
- Description:
- IC DECODER/DEMUX 1X2:4 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:295
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS139D from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin SOIC package, designed for high-speed memory decoding and data routing. It features Schottky-clamped TTL logic, 3–14 ns propagation delay (tPLH/tPHL), ±0.4 mA high-level and 4–8 mA low-level output drive, and operates over 0°C to 70°C.
For engineers reviewing the SN74ALS139D datasheet, SN74ALS139D pinout, SN74ALS139D application, or SN74ALS139D equivalent, this device serves as a legacy-compatible, buffered dual decoder with active-low enable inputs, fully specified for industrial memory subsystems and address demultiplexing where low propagation delay and TTL-level compatibility are critical.
Technical Context
The SN74ALS139D integrates two independent 2-to-4 decoders sharing no internal signal paths-each with dedicated A/B select inputs and active-low G enable. Its Schottky-clamped ALS (Advanced Low-Power Schottky) architecture delivers faster switching than standard LS while maintaining TTL voltage thresholds and load compatibility.
All inputs are fully buffered (1 normalized load), and outputs are totem-pole (non-open-collector), supporting direct interfacing with TTL/ALS loads without pull-ups. The device exhibits symmetrical propagation delays from both select (A/B) and enable (G) inputs to any Y output, enabling predictable timing in cascaded or synchronous enable schemes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) - enables higher speed than LS with comparable power |
| Propagation Delay (tPLH/tPHL) | 3–14 ns at VCC = 4.5–5.5 V, CL = 50 pF - ensures sub-15 ns decode latency in memory access paths |
| Output Drive (IOL) | 4 mA min / 8 mA max - drives multiple TTL inputs without fanout limitation in legacy systems |
| Supply Voltage Range | 4.5 V to 5.5 V - compatible with regulated 5 V rails; not tolerant of undervoltage or overvoltage operation |
| Operating Temperature | 0°C to 70°C - rated for commercial-grade embedded and computing applications |
| Input Load | 1 normalized TTL load per input - simplifies driving circuit design and reduces loading on upstream logic |
| Enable Architecture | Dual active-low enables (1G, 2G) - supports independent channel gating or cascaded decoding with minimal external logic |
Pinout & Package
SN74ALS139D uses a 16-pin SOIC (Small Outline Integrated Circuit) package, 3.9 mm wide, 9.9 mm long, 1.75 mm max height, with 1.27 mm pitch and gull-wing leads. Pin 1 is marked by a beveled corner or notch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | 1Y0 | Active-low decoded output for first decoder, select 00 (A=0,B=0) |
| 2 | 1Y1 | Active-low decoded output for first decoder, select 01 (A=0,B=1) |
| 3 | 1Y2 | Active-low decoded output for first decoder, select 10 (A=1,B=0) |
| 4 | 1Y3 | Active-low decoded output for first decoder, select 11 (A=1,B=1) |
| 5 | 1B | Second select input for first decoder (B) |
| 6 | 1A | First select input for first decoder (A) |
| 7 | 1G | Active-low enable for first decoder - must be LOW to activate outputs |
| 8 | GND | Ground reference for all logic and output stages |
| 9 | 2Y0 | Active-low decoded output for second decoder, select 00 |
| 10 | 2Y1 | Active-low decoded output for second decoder, select 01 |
| 11 | 2Y2 | Active-low decoded output for second decoder, select 10 |
| 12 | 2Y3 | Active-low decoded output for second decoder, select 11 |
| 13 | 2B | Second select input for second decoder (B) |
| 14 | 2A | First select input for second decoder (A) |
| 15 | 2G | Active-low enable for second decoder |
| 16 | VCC | +5 V supply - powers both decoder sections and internal buffers |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent decoders | Two fully isolated 2-to-4 decoder blocks in one SOIC-16 package - eliminates need for two discrete devices and saves board space |
| Schottky-clamped ALS logic | Reduces propagation delay by ~30% vs. standard LS while maintaining TTL-compatible voltage levels and noise margins |
| Buffered inputs (1 TTL load) | Minimizes loading on upstream drivers - allows direct connection to microcontroller GPIO or bus transceivers without buffering |
| Active-low enable per decoder | Enables selective channel activation, hierarchical decoding, or time-multiplexed data routing without additional gates |
| High-speed memory interface support | Propagation delay <15 ns ensures decode overhead remains negligible relative to typical 55–70 ns fast SRAM access times |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
Use Scenario: Decoding 2-bit address lines to select among four SRAM or ROM chips in an 8-bit microprocessor system. IC Role / Device Role / Timing Role: Dual decoder provides parallel chip-select signals with matched propagation delay, ensuring simultaneous enable of selected memory banks. Use Value: Eliminates race conditions between chip selects and reduces total decode latency to ≤14 ns - preserving system timing margin in 8 MHz Z80 or 6502 designs. |
Use Scenario: Routing control signals from a microcontroller to four distinct peripheral ICs (e.g., UART, ADC, DAC, I/O expander). IC Role / Device Role / Timing Role: Acts as address-based demultiplexer, using A/B inputs as peripheral ID and G inputs for global enable/disable control. Use Value: Enables single-port peripheral addressing with deterministic 3–14 ns response - critical for real-time interrupt-driven I/O coordination. |
| Cascaded Decoder Tree | Legacy Bus Interface |
Use Scenario: Building a 3-to-8 or 4-to-16 decoder using two SN74ALS139D units with shared select lines and daisy-chained enables. IC Role / Device Role / Timing Role: First device's outputs drive enables of second-stage decoders - leveraging active-low G inputs for hierarchical expansion. Use Value: Achieves full 3-to-8 decoding with worst-case delay of ≤28 ns (two-stage), maintaining compatibility with original TTL-based backplane timing budgets. |
Use Scenario: Interfacing modern FPGA I/O banks to legacy TTL bus systems requiring strict 5 V signaling and fanout capability. IC Role / Device Role / Timing Role: Translates FPGA-configured address/control bits into properly timed, buffered, and level-shifted TTL-compatible outputs. Use Value: Provides guaranteed 4 mA sink current and 1-TTL-load input impedance - eliminating need for discrete buffer arrays in mixed-technology upgrades. |
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 | Standard LS family; 15–25 ns propagation delay, lower drive (IOL = 8 mA typ), same pinout and function | Higher delay limits use in >8 MHz systems; suitable for cost-sensitive, non-critical timing applications | Select when absolute minimum propagation delay is not required and LS-level power/performance trade-off is acceptable |
| SN74HC139DR | CMOS HC family; 13–26 ns delay at 5 V, rail-to-rail voltage operation (2–6 V), lower ICC (<8 µA), but TTL input thresholds not guaranteed | Requires level-shifting or careful VIH/VIL margining when driven by legacy TTL; unsuitable for direct drop-in replacement without validation | Select only when migrating to CMOS infrastructure and redesigning input drive conditions - not a functional substitute for SN74ALS139D in existing TTL systems |
Compared with SN74LS139N, SN74ALS139D offers significantly faster timing and improved noise immunity; compared with SN74HC139DR, it guarantees TTL-compatible input thresholds and drive strength but consumes more static current and lacks wide-voltage flexibility.
Availability
SN74ALS139D is available at Aetrix Electronics and suitable for legacy system repair, industrial controller refurbishment, and educational electronics labs requiring stable component supply of discontinued yet widely documented TTL logic.
Supply support for SN74ALS139D 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 broad industrial, automotive, and aerospace reach.
The SN74ALS139D belongs to TI's legacy Advanced Schottky TTL (ALS) logic family, engineered specifically for high-speed memory decoding and data transmission systems where propagation delay and TTL interoperability were primary design constraints.
FAQ
What is the maximum operating frequency supported by the SN74ALS139D?
The SN74ALS139D does not specify a maximum clock or toggle frequency in its datasheet because it is a combinational logic device-not a clocked sequential circuit. Its usable speed is determined by propagation delay: worst-case tPHL/tPLH is 14 ns at 5 V, enabling reliable operation in systems with address/data setup times ≥15 ns. For example, it supports clean decoding in 8 MHz Z80 systems where address valid time exceeds 62.5 ns.
Can the SN74ALS139D be used as a 1-to-4 demultiplexer?
Yes, the SN74ALS139D can function as a dual 1-to-4 demultiplexer. In each section, the active-low G input serves as the data input, while A and B act as select lines. When G is LOW, the selected Y output goes LOW (active); all others remain HIGH. This configuration is explicitly supported in the device's function table and application notes, and is commonly used for signal routing in test equipment and protocol analyzers.
Is the SN74ALS139D pin-compatible with the SN74LS139?
Yes, the SN74ALS139D is pin-compatible and functionally identical to the SN74LS139 in D, N, and J packages. Both share identical pin assignments, truth tables, and electrical interface requirements. However, SN74ALS139D delivers faster propagation delay (3–14 ns vs. 15–25 ns) and slightly higher ICC, making it a performance upgrade within the same PCB footprint.
Does the SN74ALS139D have open-collector outputs?
No, the SN74ALS139D features totem-pole (push-pull) outputs, not open-collector. All Y outputs actively drive both HIGH and LOW states. This eliminates the need for external pull-up resistors and ensures defined logic levels under all operating conditions - a key distinction from open-collector variants like the SN74ALS138 or SN7406.
What is the recommended bypass capacitor for the SN74ALS139D?
A 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 16) and GND (pin 8) pins is recommended for the SN74ALS139D. This mitigates high-frequency supply noise generated during rapid output transitions, especially important in dense TTL layouts. For systems with multiple SN74ALS139D units, a bulk 10 µF electrolytic capacitor per 5–10 devices is also advised on the 5 V rail.
SN74ALS139D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- 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:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74ALS139D FAQ
1.How can I place an order for SN74ALS139D through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS139D 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 SN74ALS139D reliable?
The price and inventory of SN74ALS139D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS139D is usually 5 days.
3.What payment methods are accepted for SN74ALS139D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS139D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS139D?
SN74ALS139D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS139D 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 SN74ALS139D?
For technical support, including SN74ALS139D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS139D requirements.
6.How does Aetrix verify that SN74ALS139D is sourced from the original manufacturer or authorized distributors?
All SN74ALS139D 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 SN74ALS139D meets industry standards.
7.What is the process for return or replacement of SN74ALS139D?
All SN74ALS139D units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS139D, 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 SN74ALS139D part is unused and in its original packaging.
Return procedure for SN74ALS139D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS139D Tags
-
SN74HC138DR
Texas Instruments
-
TC7SB3157CFU,LF(CT
Toshiba Semiconductor and Storage
-
74CBTLV3257PW,118
Nexperia USA Inc.
-
SN74CBTLV3257PWR
Texas Instruments
-
74CBTLV3257GUX
Nexperia USA Inc.
-
74HC154BQ,118
Nexperia USA Inc.
-
P3S0200GMX
NXP USA Inc.
-
SN74CB3Q3245PWR
Texas Instruments
-
SN74CB3Q3257RGYR
Texas Instruments
-
TCA9543APWR
Texas Instruments
-
TCA9546APWR
Texas Instruments
-
SN74HC138N
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
