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

Texas Instruments SN74HCT139N

Name: SN74HCT139N
Brand: Texas Instruments
SKU: SN74HCT139N
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74HCT139N

Manufacturer:: Texas Instruments

Category:: Signal Switches, Multiplexers, Decoders

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

Datasheet:: SN74HCT139N.pdf

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

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Product details

Overview

SN74HCT139N from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in 16-pin PDIP package, operating at 4.5–5.5 V, with 10 ns typical propagation delay, ±4-mA output drive, and TTL-compatible inputs. It serves as a high-speed memory address decoder in industrial control systems requiring precise enable-controlled signal routing.

For engineers reviewing the SN74HCT139N datasheet, SN74HCT139N pinout, SN74HCT139N application, or SN74HCT139N equivalent, key selection criteria include active-low enable architecture, dual independent decoder functionality, LSTTL load drive capability (up to 10 loads), and compatibility with 5-V logic families in space-constrained through-hole designs.

Technical Context

The SN74HCT139N integrates two fully buffered, independent 2-to-4 line decoders sharing no internal logic-each with its own active-low enable (G) input. Its positive-logic decoding function maps binary inputs A/B to four active-low outputs (Y0–Y3), while G enables/disables the entire decoder section.

Designed for memory-decoding applications, it features low input current (≤1 µA), 80-µA max ICC supply current, and guaranteed switching performance across −40°C to +85°C. Propagation delay is specified at 12–51 ns depending on voltage and temperature, with output drive validated at ±4 mA at 5 V.

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage	4.5 V to 5.5 V - Ensures stable operation in standard 5-V TTL/CMOS systems without level-shifting.
Propagation Delay (tpd)	12 ns (min) to 40 ns (max) at 5.5 V - Enables sub-25-MHz address decoding in fast memory subsystems.
Output Drive	±4 mA at 5 V - Directly interfaces with 10 LSTTL loads without external buffers.
Input Compatibility	TTL-voltage compatible - Accepts standard TTL logic thresholds (VIH = 2 V, VIL = 0.8 V) while powered from 5-V rail.
Quiescent Current (ICC)	80 µA max - Minimizes standby power in battery-backed or energy-sensitive control modules.
Operating Temperature	−40°C to +85°C - Qualified for industrial-grade embedded applications including PLC I/O modules.

Pinout & Package

SN74HCT139N uses a 16-pin plastic dual in-line package (PDIP-N) with 19.31 mm × 6.35 mm body size and through-hole mounting. Pin 1 is located at the top-left corner adjacent to the notch or dot marking.

Pin/Terminal	Circuit Role	Design Meaning
1, 15	G1, G2 (Enable)	Active-low enables for Decoder 1 and Decoder 2 - tied low to activate; high disables all outputs (Y0–Y3) to high-impedance state.
2, 3, 5, 6	A1, B1, A2, B2 (Select Inputs)	Binary address inputs per decoder - A/B determine which of four outputs (Y0–Y3) goes low; unused inputs must be tied to VCC or GND.
4, 7, 10, 13, 12, 14, 9, 11	Y01–Y31, Y02–Y32 (Outputs)	Eight active-low decoded outputs - each decoder drives four independent outputs; outputs sink current when active.
8	GND	Ground reference for all logic and power domains - requires low-impedance connection to system ground plane.
16	VCC	Positive supply rail - requires local 0.1-µF ceramic bypass capacitor placed within 5 mm of pin for noise suppression.

Key Features

Feature	Design Value
Dual independent decoders	Two fully isolated 2-to-4 line decoders share only VCC/GND - enables parallel address decoding or split data routing without crosstalk.
Active-low enable control	G1/G2 pins allow hierarchical cascading - one decoder can gate another's enable, supporting 3-to-8 or 4-to-16 expansion without external logic.
Full input buffering	Each input presents only one normalized LSTTL load - reduces fanout burden on upstream drivers and maintains timing integrity.
High-speed memory interface	Typical tpd = 10 ns at 5 V - ensures decoder delay is negligible versus typical SRAM access times (>25 ns), preserving system timing margins.
TTL-compatible input thresholds	VIH = 2 V, VIL = 0.8 V - interoperates directly with legacy 74LS/74ALS devices without level translation in mixed-logic systems.

Applications

Industrial PLC Address Decoding	Legacy Bus Interface Logic
Use Scenario: Selecting one of four I/O expansion modules on a Modbus RTU slave board using 2-bit address lines from microcontroller GPIO. IC Role / Device Role / Timing Role: Dual decoder provides simultaneous chip-select signals for up to four peripheral ICs; active-low enables synchronize with bus cycle timing. Use Value: Eliminates need for discrete NAND gates or CPLD-based decoding, reducing BOM count and PCB area in cost-sensitive automation hardware.	Use Scenario: Translating 2-bit ISA bus address lines (A0–A1) into four separate device-select signals for legacy PC add-in cards. IC Role / Device Role / Timing Role: Acts as address-space partitioner - each decoder section handles one pair of peripherals; enables coexistence of multiple legacy devices on shared data bus. Use Value: Maintains strict ISA timing compliance with ≤40 ns max propagation delay, avoiding bus contention or setup violations during 8-MHz bus cycles.
Memory Expansion in Microcontroller Systems	LED Matrix Row Driver Enable Logic
Use Scenario: Expanding external SRAM capacity on an MSP430F5xx-based data logger by selecting between four 32-KB memory banks. IC Role / Device Role / Timing Role: Provides bank-select outputs synchronized to address strobe; G inputs accept write-enable polarity matching. Use Value: Delivers deterministic 12–40 ns decode latency across full temperature range, ensuring reliable memory access under varying ambient conditions.	Use Scenario: Driving row-enable lines in a 16×16 LED matrix where two microcontroller pins select one of four 4-row segments. IC Role / Device Role / Timing Role: Converts binary row-group address into active-low segment enables; outputs sink current directly into PNP transistor bases. Use Value: Leverages ±4-mA output drive to eliminate base resistors for discrete transistors, simplifying layout and improving scan rate consistency.

Industrial PLC Address Decoding

Legacy Bus Interface Logic

Use Scenario: Selecting one of four I/O expansion modules on a Modbus RTU slave board using 2-bit address lines from microcontroller GPIO.

IC Role / Device Role / Timing Role: Dual decoder provides simultaneous chip-select signals for up to four peripheral ICs; active-low enables synchronize with bus cycle timing.

Use Value: Eliminates need for discrete NAND gates or CPLD-based decoding, reducing BOM count and PCB area in cost-sensitive automation hardware.

Use Scenario: Translating 2-bit ISA bus address lines (A0–A1) into four separate device-select signals for legacy PC add-in cards.

IC Role / Device Role / Timing Role: Acts as address-space partitioner - each decoder section handles one pair of peripherals; enables coexistence of multiple legacy devices on shared data bus.

Use Value: Maintains strict ISA timing compliance with ≤40 ns max propagation delay, avoiding bus contention or setup violations during 8-MHz bus cycles.

Memory Expansion in Microcontroller Systems

LED Matrix Row Driver Enable Logic

Use Scenario: Expanding external SRAM capacity on an MSP430F5xx-based data logger by selecting between four 32-KB memory banks.

IC Role / Device Role / Timing Role: Provides bank-select outputs synchronized to address strobe; G inputs accept write-enable polarity matching.

Use Value: Delivers deterministic 12–40 ns decode latency across full temperature range, ensuring reliable memory access under varying ambient conditions.

Use Scenario: Driving row-enable lines in a 16×16 LED matrix where two microcontroller pins select one of four 4-row segments.

IC Role / Device Role / Timing Role: Converts binary row-group address into active-low segment enables; outputs sink current directly into PNP transistor bases.

Use Value: Leverages ±4-mA output drive to eliminate base resistors for discrete transistors, simplifying layout and improving scan rate consistency.

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual decoder/demultiplexer applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74HC139N	Higher VCC range (2–6 V); slower tpd (24–60 ns); lower drive (±4 mA at 6 V only).	Preferred for mixed-voltage systems (3.3 V/5 V) but unsuitable for timing-critical memory decoding above 10 MHz.	Select SN74HC139N only if supply flexibility outweighs speed requirements; verify VIH/VIL thresholds match host logic family.
74LS139N	Bipolar TTL technology; higher ICC (18 mA typ); faster tpd (15 ns typ) but incompatible with CMOS input leakage specs.	Legacy replacement in existing LS-based designs; not recommended for new designs due to power and noise sensitivity.	Use 74LS139N solely for drop-in repair of vintage equipment; avoid in new designs requiring low power or ESD robustness.

Compared with SN74HC139N and 74LS139N, the SN74HCT139N uniquely balances TTL input compatibility, 5-V-only optimization, and sub-40 ns timing - making it the optimal choice for industrial 5-V systems where signal integrity and legacy interoperability are critical.

Availability

SN74HCT139N is available at Aetrix Electronics and suitable for industrial PLCs, legacy bus adapters, microcontroller memory expansion, and LED matrix controllers requiring stable component supply and long-term obsolescence management.

Supply support for SN74HCT139N 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 global semiconductor leader specializing in analog, embedded processing, and logic solutions, with over 90 years of innovation in industrial, automotive, and communications markets.

The SN74HCT139N belongs to TI's 74HCT logic family, engineered specifically for high-speed memory decoding and data-routing applications where TTL compatibility, low power, and precise timing are essential.

FAQ

What is the maximum clock frequency supported by SN74HCT139N in demultiplexing mode?

The SN74HCT139N does not operate on a clock signal-it is combinational logic. Its effective maximum operating frequency depends on propagation delay and system timing margins. With a worst-case tpd of 51 ns (at 4.5 V, −40°C), it supports address/data routing in systems with cycle times ≥102 ns (≈9.8 MHz), assuming setup/hold constraints are met by upstream drivers.

Can SN74HCT139N drive LEDs directly without current-limiting resistors?

No. While SN74HCT139N outputs can sink up to 4 mA per pin, direct LED connection risks exceeding absolute maximum ratings and violates recommended operating conditions. A series current-limiting resistor is mandatory to constrain forward current within 4 mA and maintain VOL ≤ 0.33 V at 4 mA, as specified in the datasheet.

Is SN74HCT139N pin-compatible with SN74LS139N?

Yes-SN74HCT139N and SN74LS139N share identical 16-pin PDIP pinout, terminal functions, and logic behavior. However, SN74HCT139N draws significantly less supply current (80 µA vs. 18 mA) and offers improved noise immunity, making it a functional upgrade with no PCB changes required.

How should unused inputs be handled on SN74HCT139N?

All unused inputs on SN74HCT139N-including A, B, and G pins not assigned to active decoders-must be tied to either VCC or GND. Floating inputs cause undefined output states and increased ICC. For example, unused G2 should be pulled high to disable Decoder 2, preventing unintended output activation.

Does SN74HCT139N support mixed-voltage operation (e.g., 3.3-V inputs with 5-V supply)?

No. SN74HCT139N inputs are TTL-compatible (VIH = 2 V min), not 3.3-V CMOS-compatible. Applying 3.3-V logic levels may result in marginal or non-functional VIH recognition. For mixed-voltage systems, use SN74AHCT139N (which guarantees VIH = 2 V min at VCC = 4.5–5.5 V) or add level-shifting circuitry.

SN74HCT139N Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74HCT

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:: 4mA, 4mA

Voltage Supply Source:: Single Supply

Voltage - Supply:: 4.5V ~ 5.5V

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 16-PDIP

SN74HCT139N FAQ

1.How can I place an order for SN74HCT139N through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74HCT139N 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 SN74HCT139N reliable?

The price and inventory of SN74HCT139N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HCT139N is usually 5 days.

3.What payment methods are accepted for SN74HCT139N?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HCT139N transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74HCT139N?

SN74HCT139N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74HCT139N 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 SN74HCT139N?

For technical support, including SN74HCT139N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HCT139N requirements.

6.How does Aetrix verify that SN74HCT139N is sourced from the original manufacturer or authorized distributors?

All SN74HCT139N 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 SN74HCT139N meets industry standards.

7.What is the process for return or replacement of SN74HCT139N?

All SN74HCT139N units undergo pre-shipment inspection (PSI). If there is an issue with SN74HCT139N, 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 SN74HCT139N part is unused and in its original packaging.

Return procedure for SN74HCT139N:

1.Submit a request within 90 days.

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

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