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

Texas Instruments SN74LS139AN

Name: SN74LS139AN
Brand: Texas Instruments
SKU: SN74LS139AN
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LS139AN

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

Package:: 16-DIP (0.300", 7.62mm)

Datasheet:: SN74LS139AN.pdf

Description:: IC DECODER/DEMUX 1X2:4 16DIP

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Product details

Overview

SN74LS139AN from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin PDIP package, operating from 4.75 V to 5.25 V with typical propagation delay of 15 ns at V_CC = 5 V and T_A = 25 °C, used for address decoding in TTL-based microprocessor systems and memory selection logic.

For engineers reviewing the SN74LS139AN datasheet, SN74LS139AN pinout, SN74LS139AN application, or SN74LS139AN equivalent, this page delivers verified functional identity, confirmed DC/AC electrical specs, validated pin assignments, real-world use cases in legacy control systems, and two technically documented alternative parts with explicit compatibility boundaries.

Technical Context

The SN74LS139AN implements two independent 2-to-4 line decoders, each with active-low enable (G̅) and active-low outputs (Y₀–Y₃). Each decoder accepts two binary inputs (A, B) and generates four mutually exclusive low-level outputs based on input state and enable status.

It uses standard TTL circuitry with Schottky-clamped transistors, delivering guaranteed fan-out of 20 LS-TTL loads, input clamp diodes for transient protection, and output short-circuit protection rated to 60 mA per channel under continuous operation.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	4.75 V to 5.25 V - Ensures stable operation within standard TTL supply tolerance; outside this range risks incorrect logic states or device damage.
Propagation Delay t_pd	15 ns max (A/B to Y) - Defines maximum time between input change and valid output assertion; critical for synchronous timing budgets in bus decoding.
Output Drive	I_OH = –0.4 mA / I_OL = 8 mA - Specifies high-state sourcing and low-state sinking capability; supports direct interface to multiple LS-TTL inputs without buffers.
Input Voltage Thresholds	V_IH = 2.0 V min / V_IL = 0.8 V max - Guarantees reliable recognition of logic HIGH/LOW from upstream TTL or CMOS drivers.
Operating Temperature	0 °C to +70 °C - Validated for commercial-grade environments only; not rated for extended industrial or military temperature ranges.
Package	PDIP (N), 16-pin - Through-hole mounting compatible with legacy PCB assembly processes and prototyping breadboards.

Pinout & Package

SN74LS139AN is housed in a 16-pin plastic dual in-line package (PDIP-N), 0.300-inch wide body, with 0.100-inch lead pitch and standard DIP footprint (JEDEC MS-001).

Pin/Terminal	Circuit Role	Design Meaning
1, 15	Decoder 1 & 2 Enable (G̅)	Active-low chip select; both must be LOW for respective decoder outputs to respond to A/B inputs.
2, 3, 5, 6	Decoder 1 Inputs (A1, B1, G̅1) & Outputs (Y01–Y31)	First decoder: A1/B1 accept binary address; Y01–Y31 assert LOW for matching codes when G̅1 = LOW.
8, 10, 11, 12, 13	GND, Decoder 2 Inputs (A2, B2, G̅2), Outputs (Y02–Y32)	Second independent decoder with identical function; shares no internal resources with Decoder 1.
16	V_CC	Positive supply rail; must be decoupled locally with 0.1 µF ceramic capacitor to suppress switching noise.

Key Features

Feature	Design Value
Dual independent decoders	Enables simultaneous decoding of two separate 2-bit address buses-e.g., I/O port select and peripheral memory block select-without external gating.
Active-low enable & outputs	Direct compatibility with common active-low chip select architectures in 8-bit microprocessor systems (e.g., Z80, 8085) and legacy memory modules.
TTL-compatible input thresholds	Accepts standard TTL logic levels without level-shifting; eliminates need for interface buffers when driven by 74LS, 74S, or 74F series devices.
Short-circuit protected outputs	Withstands indefinite output short to V_CC or GND at 25 °C without latch-up or permanent degradation-critical for field-serviceable industrial controllers.

Applications

Industrial PLC I/O Expansion	Legacy Microprocessor Address Decoding
Use Scenario: Expanding discrete input/output capacity in programmable logic controllers using parallel bus architecture. IC Role / Device Role / Timing Role: Decoder selects one of four I/O module slots via 2-bit slot address; enables corresponding module's data bus transceivers. Use Value: Reduces address bus routing complexity by replacing discrete NAND/NOR gates; ensures deterministic 15 ns decode latency across all four channels.	Use Scenario: Mapping memory-mapped peripherals in 8-bit embedded systems such as test equipment or instrumentation controllers. IC Role / Device Role / Timing Role: Translates upper address bits into chip-select signals for UART, timer, and ADC peripherals sharing a common data bus. Use Value: Provides glitch-free, fully decoded CS asserts with no external timing components-meeting strict setup/hold requirements of 8085-compatible peripherals.
EPROM Memory Bank Selection	LED Segment Driver Enable Logic
Use Scenario: Selecting among four 8K×8 EPROM banks in vintage computer or firmware development systems. IC Role / Device Role / Timing Role: Uses A14/A15 address lines to activate one EPROM chip-enable while keeping others disabled, preventing bus contention. Use Value: Eliminates need for discrete inverters and AND gates; guarantees monotonic output transitions during address changes-avoiding read corruption during bank switches.	Use Scenario: Controlling common-anode 7-segment displays in multiplexed digital panel meters or diagnostic interfaces. IC Role / Device Role / Timing Role: Drives segment driver enable lines (e.g., ULN2003 inputs) to cycle through four digit positions synchronously with display refresh. Use Value: Delivers precise, low-jitter digit enable timing (15 ns skew) essential for flicker-free display operation at >100 Hz refresh rates.

Industrial PLC I/O Expansion

Legacy Microprocessor Address Decoding

Use Scenario: Expanding discrete input/output capacity in programmable logic controllers using parallel bus architecture.

IC Role / Device Role / Timing Role: Decoder selects one of four I/O module slots via 2-bit slot address; enables corresponding module's data bus transceivers.

Use Value: Reduces address bus routing complexity by replacing discrete NAND/NOR gates; ensures deterministic 15 ns decode latency across all four channels.

Use Scenario: Mapping memory-mapped peripherals in 8-bit embedded systems such as test equipment or instrumentation controllers.

IC Role / Device Role / Timing Role: Translates upper address bits into chip-select signals for UART, timer, and ADC peripherals sharing a common data bus.

Use Value: Provides glitch-free, fully decoded CS asserts with no external timing components-meeting strict setup/hold requirements of 8085-compatible peripherals.

EPROM Memory Bank Selection

LED Segment Driver Enable Logic

Use Scenario: Selecting among four 8K×8 EPROM banks in vintage computer or firmware development systems.

IC Role / Device Role / Timing Role: Uses A14/A15 address lines to activate one EPROM chip-enable while keeping others disabled, preventing bus contention.

Use Value: Eliminates need for discrete inverters and AND gates; guarantees monotonic output transitions during address changes-avoiding read corruption during bank switches.

Use Scenario: Controlling common-anode 7-segment displays in multiplexed digital panel meters or diagnostic interfaces.

IC Role / Device Role / Timing Role: Drives segment driver enable lines (e.g., ULN2003 inputs) to cycle through four digit positions synchronously with display refresh.

Use Value: Delivers precise, low-jitter digit enable timing (15 ns skew) essential for flicker-free display operation at >100 Hz refresh rates.

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual 2-to-4 line decoder applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS139ADR	SOIC-16 package; RoHS-compliant NiPdAu lead finish; MSL Level-1 rating; same electrical specs and pinout.	Suitable for automated SMT assembly; not compatible with through-hole sockets or hand-soldered prototypes.	Select SN74LS139ADR only when board design uses SOIC footprints and reflow process is qualified for Level-1 moisture sensitivity.
SN74HC139N	High-speed CMOS technology; V_CC = 2 V–6 V; t_pd = 19 ns typical at 4.5 V; higher noise immunity but requires level translation if interfacing with legacy TTL.	Enables mixed-voltage system integration (e.g., 3.3 V MCU controlling 5 V peripherals); incompatible with direct TTL fan-out loading.	Choose SN74HC139N only when power supply flexibility or noise margin outweighs need for plug-in TTL compatibility.

Compared with SN74LS139AN, SN74LS139ADR offers identical functionality in surface-mount form for modern production, while SN74HC139N provides wider voltage range and lower static current but requires careful interface design to avoid logic threshold mismatch in pure TTL systems.

Availability

SN74LS139AN is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment refurbishment, and educational electronics labs requiring stable component supply with full traceability and long-term obsolescence management.

Supply support for SN74LS139AN 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 consumer market reach.

The SN74LS139AN belongs to TI's legacy 74LS logic family, designed specifically for robust, low-cost, TTL-compatible digital control functions in non-automotive commercial and industrial equipment where reliability and second-source availability are prioritized over ultra-low power or high speed.

FAQ

What is the maximum clock frequency supported by SN74LS139AN?

The SN74LS139AN is not a clocked sequential device-it is a combinational decoder with no internal clock. Its usable switching rate is limited by propagation delay (15 ns max) and system-level setup/hold timing. In practice, SN74LS139AN reliably supports address decoding in 8-bit systems running up to 10 MHz bus cycles, provided external timing margins accommodate its 15 ns t_pd.

Can SN74LS139AN drive LEDs directly?

No-SN74LS139AN outputs are designed for logic-level interfacing, not power driving. Its I_OL = 8 mA is insufficient for most indicator LEDs (typically requiring 10–20 mA). To drive LEDs, use SN74LS139AN outputs to control transistor switches or dedicated LED drivers like ULN2003. Direct connection risks output voltage droop and accelerated wear.

Is SN74LS139AN pin-compatible with SN74LS138N?

No-SN74LS139AN and SN74LS138N are functionally and physically distinct. SN74LS139AN is a dual 2-to-4 decoder in 16-pin PDIP with two independent enables and eight total outputs. SN74LS138N is a single 3-to-8 decoder in 16-pin PDIP with three enables and eight outputs. Pin assignments, truth tables, and enable logic differ fundamentally; they are not interchangeable without PCB redesign.

Does SN74LS139AN support mixed-voltage operation (e.g., 3.3 V inputs)?

No-SN74LS139AN is strictly a 5 V TTL device. Its input thresholds (V_IL = 0.8 V, V_IH = 2.0 V) are optimized for 5 V logic families. Applying 3.3 V signals may result in marginal or undefined logic states due to insufficient noise margin. For 3.3 V–5 V interfacing, use level translators or select a CMOS variant like SN74HC139N.

What is the recommended bypass capacitor for SN74LS139AN?

A 0.1 µF ceramic capacitor placed as close as possible between V_CC (Pin 16) and GND (Pin 8) is mandatory for stable operation. This suppresses high-frequency switching noise generated during output transitions. For systems with multiple SN74LS139AN devices, add one 0.1 µF cap per IC plus a bulk 4.7 µF electrolytic capacitor near the power entry point to handle low-frequency ripple.

SN74LS139AN Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LS

Package/Case:: 16-DIP (0.300", 7.62mm)

Packaging:: Tube

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:: 4.75V ~ 5.25V

Operating Temperature:: 0°C ~ 70°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 16-PDIP

SN74LS139AN FAQ

1.How can I place an order for SN74LS139AN through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS139AN 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 SN74LS139AN reliable?

The price and inventory of SN74LS139AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS139AN is usually 5 days.

3.What payment methods are accepted for SN74LS139AN?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS139AN transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS139AN?

SN74LS139AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS139AN 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 SN74LS139AN?

For technical support, including SN74LS139AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS139AN requirements.

6.How does Aetrix verify that SN74LS139AN is sourced from the original manufacturer or authorized distributors?

All SN74LS139AN 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 SN74LS139AN meets industry standards.

7.What is the process for return or replacement of SN74LS139AN?

All SN74LS139AN units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS139AN, 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 SN74LS139AN part is unused and in its original packaging.

Return procedure for SN74LS139AN:

1.Submit a request within 90 days.

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

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