My Inquiry
My Account
Texas Instruments SN74LS139AD
- Part No.:
- SN74LS139AD
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS139AD.pdf
- Description:
- IC DECODER/DEMUX 1X2:4 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,200
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74LS139AD from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin SOIC package, operating over 0°C to 70°C, with typical propagation delay of 25 ns at VCC = 5 V and IOL = 8 mA, used for address decoding in TTL-based microprocessor systems and memory selection logic.
For engineers reviewing the SN74LS139AD datasheet, SN74LS139AD pinout, SN74LS139AD application, or SN74LS139AD equivalent, this page delivers verified functional specifications, validated pin assignments, confirmed industrial use cases, and two technically documented alternative parts for legacy TTL system design and component obsolescence mitigation.
Technical Context
The SN74LS139AD implements two independent 2-to-4 line decoders, each with active-low enable (G̅) and active-low outputs (Y̅₀–Y̅₃), supporting standard TTL voltage thresholds and fan-out of 20 LS-TTL loads. Its logic function follows Boolean expressions Y̅₀ = G̅·A̅·B̅, Y̅₁ = G̅·A̅·B, Y̅₂ = G̅·A·B̅, Y̅₃ = G̅·A·B.
It operates strictly within the LS-TTL family electrical parameters: VCC = 4.75–5.25 V, ICC = 24 mA max per decoder, and guaranteed noise margin of 0.4 V under worst-case conditions. No internal latching, clocking, or programmability is present - it is purely combinational logic.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures compatibility with legacy 74LS-series systems and defined DC noise immunity |
| Propagation Delay | 25 ns max (tPLH/tPHL) - determines maximum clock rate for synchronous address decode paths |
| Supply Voltage | 4.75–5.25 V - requires stable +5 V rail; not tolerant of undervoltage or overvoltage operation |
| Output Drive | IOL = 8 mA / IOH = –0.4 mA - supports direct interfacing to multiple LS-TTL inputs without buffers |
| Operating Temperature | 0°C to 70°C - rated for commercial-grade environments only, not extended or military range |
| Package Type | SOIC (D) - 300-mil wide, 16-pin surface-mount package compatible with standard reflow profiles |
| Pin Count | 16 - includes dual decoder inputs (A₀/B₀, A₁/B₁), dual enables (G̅₀/G̅₁), eight outputs (Y̅₀–Y̅₇), VCC, and GND |
Pinout & Package
SN74LS139AD uses a 16-pin SOIC (D) package with 1.27 mm pitch, 7.5 mm body width, and 2.0 mm max height. Pin 1 is located at the top-left corner with notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | G̅₀ (Enable 0) | Active-low enable for first decoder; must be low for Y̅₀–Y̅₃ to respond to A₀/B₀ |
| 2 | B₀ | LSB input for first decoder; defines output selection with A₀ |
| 3 | A₀ | MSB input for first decoder; paired with B₀ to select one of four active-low outputs |
| 4–7 | Y̅₀–Y̅₃ | Active-low decoded outputs of first decoder; only one asserted per input combination |
| 8 | GND | Ground reference for all logic and output stages |
| 9–12 | Y̅₄–Y̅₇ | Active-low decoded outputs of second decoder; functionally identical to Y̅₀–Y̅₃ |
| 13 | A₁ | MSB input for second decoder; paired with B₁ to select one of four outputs |
| 14 | B₁ | LSB input for second decoder; defines output selection with A₁ |
| 15 | G̅₁ (Enable 1) | Active-low enable for second decoder; independent control from G̅₀ |
| 16 | VCC | +5 V supply for both decoders; bypass capacitor required near pin for noise suppression |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent decoders | Enables compact address decoding for two separate memory or peripheral blocks without external gating |
| Active-low outputs and enables | Direct interface to common active-low chip-select inputs on RAM, ROM, and I/O devices |
| Standard LS-TTL compatibility | Guaranteed interoperability with 74LS00, 74LS04, 74LS32, and other LS-family logic in mixed-signal boards |
| No internal latch or clock | Eliminates timing constraints from setup/hold requirements - pure combinatorial response to inputs |
| Commercial temperature grade | Validated performance across full 0°C–70°C range, suitable for office, lab, and non-harsh industrial enclosures |
Applications
| Memory Address Decoding | Peripheral Selection Logic |
|---|---|
Use Scenario: Selecting one of four 8K×8 RAM chips in a 32K-byte memory subsystem using upper address bits A14–A15. IC Role / Device Role / Timing Role: Dual decoder maps A14/A15 to four chip-select lines (CS0–CS3), enabling only one RAM bank per access cycle. Use Value: Reduces external logic count by eliminating discrete NAND gates; maintains <25 ns decode latency critical for 4 MHz Z80 or 8085 bus timing. | Use Scenario: Assigning unique chip-select signals to UART, parallel port, timer, and interrupt controller in an 8-bit embedded controller board. IC Role / Device Role / Timing Role: SN74LS139AD provides four dedicated active-low enables, each routed to a different peripheral's CE̅ input. Use Value: Enables deterministic peripheral arbitration without bus contention; supports simultaneous decode of two independent peripheral groups via separate enables G̅₀/G̅₁. |
| I/O Port Expansion | Legacy System Bus Interface |
Use Scenario: Expanding GPIO capability in a vintage industrial PLC using 74LS244 octal buffers controlled by decoded address lines. IC Role / Device Role / Timing Role: SN74LS139AD generates strobe enables for four banks of 74LS244, allowing dynamic selection of 32 total I/O lines. Use Value: Achieves scalable I/O without FPGA or microcontroller - leverages fixed-function TTL for deterministic real-time response. | Use Scenario: Interfacing modern peripherals to a 1980s-era S-100 bus system requiring strict TTL-level timing and voltage compliance. IC Role / Device Role / Timing Role: SN74LS139AD serves as bus-address decoder, translating S-100 address lines A14/A15 into device-specific selects while meeting 40 ns max decode window. Use Value: Preserves original bus timing integrity; avoids level-shifting or delay penalties introduced by CMOS translators. |
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 | Same logic function and pinout; RoHS-compliant NiPdAu lead finish; MSL Level-1 rating; tape-and-reel packaging (2500 pcs) | Identical use cases; preferred for new production due to RoHS compliance and automated assembly support | Select SN74LS139ADR when initiating new designs or high-volume manufacturing requiring lead-free compliance and SMT placement. |
| SN74LS139AN | Same logic and timing; PDIP (N) through-hole package; 25-piece tube packaging; same 0°C–70°C range | Suitable for prototyping, repair, and legacy board rework where SOIC footprint is unavailable | Choose SN74LS139AN for hand-soldered prototypes, field repairs, or replacement on through-hole PCBs originally designed for DIP sockets. |
Compared with SN74LS139AD, SN74LS139ADR offers RoHS compliance and optimized packaging for SMT lines, while SN74LS139AN retains identical functionality in a serviceable through-hole format - neither is pin-compatible with the obsolete SN74LS139AD, but both share identical logic behavior and timing.
Availability
SN74LS139AD is available at Aetrix Electronics and suitable for memory address decoding, peripheral selection logic, I/O port expansion, and legacy system bus interface applications requiring stable component supply and long-term sourcing continuity.
Supply support for SN74LS139AD 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 communications product portfolios.
The SN74LS139AD belongs to TI's legacy 74LS logic family, designed specifically for reliable, low-power, TTL-compatible digital control and address decoding in commercial-grade computing and instrumentation systems.
FAQ
Is SN74LS139AD still in active production?
No, SN74LS139AD is marked as Obsolete in TI's official packaging documentation. It is no longer manufactured, though limited legacy stock may be available through authorized distributors. For new designs, TI recommends SN74LS139ADR (RoHS-compliant SOIC) or SN74LS139AN (PDIP) as functionally identical replacements with active production status and full datasheet support.
What is the maximum operating frequency supported by SN74LS139AD?
SN74LS139AD does not specify a maximum clock frequency because it is a purely combinational device with no internal clock. Its usable switching speed is determined by propagation delay: 25 ns max (tPLH/tPHL) at VCC = 5 V and IOL = 8 mA. This supports reliable operation in systems with address strobe widths ≥40 ns, such as 4 MHz Z80 or 8085-based buses.
Can SN74LS139AD drive LEDs directly?
Yes, SN74LS139AD can drive standard 5 mA LEDs directly via its active-low outputs (Y̅₀–Y̅₇), provided a current-limiting resistor is used between VCC and the LED anode. Each output sinks up to 8 mA (IOL), sufficient for low-current indicator LEDs. Do not connect LEDs between output and GND without the resistor, as that would exceed absolute maximum ratings.
Does SN74LS139AD require pull-up resistors on its outputs?
No, SN74LS139AD does not require external pull-up resistors on its outputs when driving standard LS-TTL or LSTTL-compatible inputs, as its outputs are fully buffered and specified to drive 20 LS-TTL loads directly. Pull-ups are only needed if interfacing with open-collector systems, CMOS inputs, or when implementing wired-OR logic - which is not the intended use case for SN74LS139AD.
How does SN74LS139AD differ from SN74LS138?
SN74LS139AD is a dual 2-line-to-4-line decoder with two independent enables (G̅₀/G̅₁) and active-low outputs, while SN74LS138 is a single 3-line-to-8-line decoder with three enables (E₁, E₂̅, E₃̅) and active-low outputs. The SN74LS139AD cannot replace SN74LS138 in 3-bit decode applications, nor vice versa - they serve distinct address-width requirements and have incompatible pinouts and truth tables.
SN74LS139AD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- 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:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74LS139AD FAQ
1.How can I place an order for SN74LS139AD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS139AD 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 SN74LS139AD reliable?
The price and inventory of SN74LS139AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS139AD is usually 5 days.
3.What payment methods are accepted for SN74LS139AD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS139AD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS139AD?
SN74LS139AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS139AD 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 SN74LS139AD?
For technical support, including SN74LS139AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS139AD requirements.
6.How does Aetrix verify that SN74LS139AD is sourced from the original manufacturer or authorized distributors?
All SN74LS139AD 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 SN74LS139AD meets industry standards.
7.What is the process for return or replacement of SN74LS139AD?
All SN74LS139AD units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS139AD, 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 SN74LS139AD part is unused and in its original packaging.
Return procedure for SN74LS139AD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74LS139AD 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…
