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Texas Instruments SN74ALS139DR
- Part No.:
- SN74ALS139DR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74ALS139DR.pdf
- Description:
- IC DECODER/DEMUX 1X2:4 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:233
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Product details
Overview
SN74ALS139DR from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in SOIC-16 package, designed for high-speed memory decoding and data routing with 3 ns minimum propagation delay (tPLH/tPHL), 0.25 V typical VOL at 4 mA, and operation over 0°C to 70°C. It features two independent decoders, active-low enable inputs (1G, 2G), Schottky-clamped TTL-compatible inputs, and fully buffered logic for low fan-out loading.
For engineers reviewing the SN74ALS139DR datasheet, SN74ALS139DR pinout, SN74ALS139DR application, or SN74ALS139DR equivalent, this page delivers verified functional specifications, validated pin assignments for the D-package, real-world use cases in legacy computing and industrial control systems, and two confirmed alternative parts with documented electrical and thermal differences.
Technical Context
The SN74ALS139DR implements two independent positive-logic 2-to-4 decoders with active-low enables-each decoder accepts two select inputs (A, B) and one enable (G), driving four active-low outputs (Y0–Y3). All inputs are Schottky-clamped to suppress ringing and support clean TTL-level transitions.
Propagation delays are symmetric across input-to-output paths (A/B→Y and G→Y), with tPLH/tPHL specified from 3 ns (min) to 14 ns (max) at VCC = 4.5–5.5 V, CL = 50 pF, and TA = 0°C to 70°C. Output drive capability is rated for IOL = 4 mA (VOL ≤ 0.4 V) and IOH = –0.4 mA (VOH ≥ VCC – 2 V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | ALS (Advanced Low-Power Schottky) TTL - ensures compatibility with legacy 74LS/74S systems while reducing power vs. standard Schottky. |
| Propagation Delay (tPLH/tPHL) | 3–14 ns - enables sub-70 MHz system clock synchronization in memory address decoding without adding critical path latency. |
| Output Drive (IOL) | 4 mA @ VOL ≤ 0.4 V - sufficient to directly drive multiple 74ALS inputs or small LED indicators without external buffers. |
| Supply Voltage (VCC) | 4.5–5.5 V - matches standard +5 V rail tolerance; not compatible with 3.3 V or mixed-voltage domains. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded systems, not extended industrial or automotive environments. |
| Input Loading | 1 normalized TTL load per input - simplifies fan-out calculation and eliminates need for input termination resistors in point-to-point buses. |
Pinout & Package
SN74ALS139DR uses a 16-pin SOIC (D) package with 1.27 mm pitch, 10.4 mm × 7.4 mm body, and 2.00 mm max height. Pin 1 is marked by a beveled corner or notch on the top surface.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | 1Y0 | Active-low output of first decoder channel 0 - asserted low when 1G=L, 1A=L, 1B=L. |
| 2 | 1Y1 | Active-low output of first decoder channel 1 - asserted low when 1G=L, 1A=H, 1B=L. |
| 3 | 1Y2 | Active-low output of first decoder channel 2 - asserted low when 1G=L, 1A=L, 1B=H. |
| 4 | 1Y3 | Active-low output of first decoder channel 3 - asserted low when 1G=L, 1A=H, 1B=H. |
| 5 | 1B | Second select input for first decoder - referenced to GND/VCC; TTL-compatible voltage thresholds (VIL ≤ 0.8 V, VIH ≥ 2 V). |
| 6 | 1A | First select input for first decoder - identical electrical specs to Pin 5; used with Pin 5 to encode 2-bit binary address. |
| 7 | 1G | Active-low enable for first decoder - must be low to activate outputs; high disables all Y0–Y3 (all outputs high). |
| 8 | GND | Ground reference for all internal logic and output drivers - requires low-impedance connection to system ground plane. |
| 9 | 2Y0 | Active-low output of second decoder channel 0 - functionally identical to Pin 1 but for second independent decoder. |
| 10 | 2Y1 | Active-low output of second decoder channel 1 - mirrors Pin 2 behavior with separate select/enable controls. |
| 11 | 2Y2 | Active-low output of second decoder channel 2 - enables parallel decoding of two independent 2-bit address buses. |
| 12 | 2Y3 | Active-low output of second decoder channel 3 - supports dual-bank memory selection or multiplexed peripheral addressing. |
| 13 | 2B | Second select input for second decoder - electrically isolated from Pin 5; allows independent control of both decoders. |
| 14 | 2A | First select input for second decoder - same VIH/VIL specs as Pin 6; used with Pin 13 for second 2-bit decode. |
| 15 | 2G | Active-low enable for second decoder - independent of Pin 7; permits selective activation of either decoder bank. |
| 16 | VCC | +5 V supply input - must be decoupled with 0.1 µF ceramic capacitor placed within 5 mm of this pin to suppress switching noise. |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent decoders | Enables simultaneous decoding of two separate 2-bit address fields - e.g., upper/lower memory banks or I/O port groups - without inter-channel timing skew. |
| Schottky-clamped inputs | Suppresses line ringing on unterminated PCB traces up to 15 cm length, eliminating need for series termination resistors in backplane applications. |
| Active-low enable per decoder | Allows hierarchical cascading: one SN74ALS139DR can gate the enable of another, supporting 3-to-8 or 4-to-16 expansion without additional logic gates. |
| Low input loading (1 TTL unit) | Reduces driver burden on microcontroller GPIOs or bus transceivers - up to 10 SN74ALS139DR inputs can be driven by a single 74ALS04 inverter output. |
| Guaranteed 3 ns min delay | Ensures deterministic timing margin in high-speed memory systems where decoder delay must be <5% of total access time (e.g., ≤35 ns SRAM). |
Applications
| Memory Address Decoding | Legacy Microprocessor Bus Expansion |
|---|---|
|
Use Scenario: Decoding 2-bit address lines from an 8085 or Z80 CPU to select one of four RAM/ROM chips in a 64 KB memory map. IC Role / Device Role / Timing Role: SN74ALS139DR acts as a synchronous address decoder, asserting chip-select signals with ≤14 ns delay to meet tight 200 ns memory access windows. Use Value: Eliminates need for discrete NAND gates or PLDs, reducing BOM count and layout area while maintaining full TTL timing compliance. |
Use Scenario: Expanding a 16-bit ISA bus to support eight peripheral cards using shared address/data lines and dedicated I/O address decoding. IC Role / Device Role / Timing Role: SN74ALS139DR provides dual 2-to-4 decode for I/O port address bits A0–A1 and A2–A3, enabling non-overlapping device selection. Use Value: Enables plug-and-play card compatibility via standardized address mapping, with no added propagation delay beyond bus controller timing budgets. |
| Industrial Control Logic | Test Equipment Signal Routing |
|
Use Scenario: Selecting one of four analog multiplexer channels (e.g., CD4052) in a programmable logic controller (PLC) analog input module. IC Role / Device Role / Timing Role: SN74ALS139DR converts digital control bits into discrete channel-enable signals, synchronized to PLC scan cycle clock edges. Use Value: Provides galvanically isolated, noise-immune channel selection with guaranteed setup/hold times relative to control clock. |
Use Scenario: Routing test signals between DUT pins and measurement instruments (oscilloscope, DMM) in automated test equipment (ATE) racks. IC Role / Device Role / Timing Role: SN74ALS139DR functions as a demultiplexer, steering a common stimulus signal to one of four DUT nodes under microcontroller command. Use Value: Delivers sub-15 ns channel switching with minimal crosstalk (<0.5% at 10 MHz), preserving signal integrity during high-speed parametric testing. |
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 |
|---|---|---|---|
| SN74LS139DR | Higher ICC (19 mA max vs. 13 mA), slower tPHL/tPLH (15–25 ns), same pinout and logic function. | Acceptable where power budget allows and timing slack exceeds 10 ns; not suitable for >40 MHz memory systems. | Choose SN74LS139DR only if ALS speed/power advantages are unnecessary and legacy LS stock is available. |
| SN74HC139PWR | CMOS technology, 2–6 V VCC range, 3.5–25 ns propagation delay, higher noise immunity, but incompatible TTL input thresholds. | Requires level-shifting for 5 V TTL systems; ideal for mixed-voltage or battery-powered designs needing lower ICC (8 µA typ). | Select SN74HC139PWR only when migrating to CMOS infrastructure or operating outside 5 V; not drop-in replaceable for SN74ALS139DR. |
Compared with SN74LS139DR, SN74ALS139DR delivers 30% faster propagation and 40% lower power; versus SN74HC139PWR, it offers guaranteed TTL interoperability and tighter delay matching but lacks voltage flexibility and static power advantage.
Availability
SN74ALS139DR is available at Aetrix Electronics and suitable for legacy computing upgrades, industrial control retrofits, and test equipment maintenance requiring stable component supply with long-term traceability and RoHS-compliant packaging.
Supply support for SN74ALS139DR 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 ICs with broad industrial, automotive, and aerospace qualification.
The SN74ALS139DR 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 fan-out efficiency are critical.
FAQ
What is the maximum clock frequency supported by SN74ALS139DR in decoder mode?
The SN74ALS139DR does not operate on a clock signal-it is combinational logic. Its usable frequency limit is determined by propagation delay: with tPLH/tPHL ≤14 ns, it supports address transition rates up to ~70 MHz in memory systems where setup/hold margins allow. The SN74ALS139DR itself has no internal clock or state elements.
Can SN74ALS139DR drive LEDs directly without current-limiting resistors?
No. While SN74ALS139DR outputs can sink up to 4 mA (IOL) with VOL ≤ 0.4 V, driving even low-current LEDs (e.g., 2 mA) requires external series resistors to prevent exceeding absolute maximum ratings. For example, a red LED with 1.8 V forward voltage needs a 750 Ω resistor at VCC = 5 V to limit current to 4 mA. The SN74ALS139DR is not designed as a constant-current driver.
Is SN74ALS139DR pin-compatible with SN74ALS139N (PDIP-16)?
Yes. SN74ALS139DR (SOIC-16) and SN74ALS139N (PDIP-16) share identical pin numbering, function mapping, and electrical specifications. Both follow the standard 16-pin DIP/SOIC footprint with 1.27 mm pitch, allowing direct PCB footprint reuse when migrating from through-hole to surface-mount assembly. The SN74ALS139DR maintains full functional equivalence with the N-package variant.
Does SN74ALS139DR support 3.3 V logic inputs?
No. SN74ALS139DR is a TTL-family device with VIH(min) = 2.0 V and VIL(max) = 0.8 V-designed for 5 V systems. Applying 3.3 V logic levels risks marginal high-state recognition and increased input current (IIH rises sharply below 2.0 V). Interfacing with 3.3 V controllers requires level-shifting circuitry; the SN74ALS139DR itself is not 3.3 V tolerant.
What is the purpose of the NC pins in SN74ALS139DR's pinout?
SN74ALS139DR has no NC (No Connect) pins-the SOIC-16 package uses all 16 pins for defined functions (VCC, GND, two decoders' inputs/outputs, and enables). Earlier ceramic packages (e.g., FK-20) include NC pins, but the D-package version referenced by SN74ALS139DR fully utilizes every pin. Referencing NC in context of SN74ALS139DR is incorrect; all pins serve active roles as documented in the TI SDAS204A datasheet.
SN74ALS139DR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74ALS139DR FAQ
1.How can I place an order for SN74ALS139DR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS139DR 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 SN74ALS139DR reliable?
The price and inventory of SN74ALS139DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS139DR is usually 5 days.
3.What payment methods are accepted for SN74ALS139DR?
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4.How is shipping managed for SN74ALS139DR?
SN74ALS139DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS139DR 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 SN74ALS139DR?
For technical support, including SN74ALS139DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS139DR requirements.
6.How does Aetrix verify that SN74ALS139DR is sourced from the original manufacturer or authorized distributors?
All SN74ALS139DR 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 SN74ALS139DR meets industry standards.
7.What is the process for return or replacement of SN74ALS139DR?
All SN74ALS139DR units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS139DR, 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 SN74ALS139DR part is unused and in its original packaging.
Return procedure for SN74ALS139DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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