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Texas Instruments SN74LS139ANSR
- Part No.:
- SN74LS139ANSR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74LS139ANSR.pdf
- Description:
- IC DECODER/DEMUX 1 X 2:4 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,824
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Product details
Overview
SN74LS139ANSR from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin SOP (NS) package, operating at 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 SN74LS139ANSR datasheet, SN74LS139ANSR pinout, SN74LS139ANSR application, or SN74LS139ANSR 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 obsolescence mitigation.
Technical Context
The SN74LS139ANSR contains 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-active outputs based on input state and enable assertion.
It operates strictly within the LS-TTL logic family voltage and current thresholds: VCC = 4.75–5.25 V, IOH = –0.4 mA (max), IOL = 8 mA (min), and features standard TTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL - ensures compatibility with legacy 74LS-series bus interfaces and drive capability matching. |
| Propagation Delay | 25 ns max (tPD) - defines worst-case timing margin for synchronous address decode in 8-bit/16-bit CPU systems. |
| Supply Voltage | 4.75 V to 5.25 V - requires regulated +5 V rail; not tolerant of undervoltage or overvoltage operation. |
| Output Drive | 8 mA sink (IOL) - sufficient to directly drive multiple TTL inputs or small LED indicators without buffering. |
| Operating Temp | 0°C to 70°C - commercial-grade rating; unsuitable for extended industrial or automotive ambient environments. |
| Package | SOP (NS), 16-pin - surface-mount footprint compatible with automated assembly; 1.27 mm pitch, 8.1 mm × 10.4 mm body. |
Pinout & Package
SOP (NS) package: 16-pin small-outline plastic package, 1.27 mm lead pitch, 8.1 mm × 10.4 mm body size, 2.00 mm max height, tape-and-reel delivery (2000 pcs/reel), RoHS-compliant NiPdAu lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 15 | G̅ (Enable) | Active-low chip select per decoder; both must be low for output activation; open-collector compatible when pulled up. |
| 2, 3, 5, 6 | A, B (Inputs) | Binary address inputs per decoder; A = LSB, B = MSB; TTL-compatible thresholds ensure noise immunity in mixed-signal boards. |
| 4, 7, 12, 14, 16 | Y0–Y3, GND | Four active-low decoded outputs per decoder (pins 4,7 for U1; 12,14,16 include Y0–Y3 and GND); outputs assert low only when corresponding input code matches and G̅ is active. |
| 8 | GND | Power ground reference for both decoders; must be low-impedance connection to avoid switching noise coupling. |
| 13, 11, 9, 10 | VCC, Y0–Y3 | VCC (pin 13) supplies both sections; Y0–Y3 (pins 11,9,10,13 unused as VCC) - actual Y outputs are pins 4,7 (decoder 1) and 12,14,16 (decoder 2, with pin 16 = Y3, pin 14 = Y2, pin 12 = Y1, pin 11 = Y0). |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent decoders | Enables compact implementation of two separate 2:4 decode functions-e.g., I/O port selection and memory bank decoding-in single IC. |
| Active-low enable & outputs | Direct interface with common active-low control buses (e.g., /CS, /OE) without inverters; reduces component count in legacy designs. |
| TTL-compatible input thresholds | VIL ≤ 0.8 V / VIH ≥ 2.0 V ensures reliable recognition of signals from 74LS, 74S, and microcontroller GPIOs without level-shifting. |
| Standard 16-pin SOP footprint | Drop-in replacement for PDIP variants in space-constrained layouts; supports reflow soldering with Level-1 MSL rating. |
Applications
| Memory Address Decoding | I/O Port Selection |
|---|---|
|
Use Scenario: Selecting one of four RAM/ROM chips in an 8080 or Z80-based embedded controller using A15–A14 address lines. IC Role / Device Role / Timing Role: Dual decoder maps high-order address bits to individual /CS lines; enables banked memory architecture with zero wait-state access. Use Value: Eliminates discrete gate logic; provides deterministic 25 ns decode latency aligned with CPU clock timing budgets. |
Use Scenario: Routing data between microprocessor and four peripheral devices (UART, ADC, DAC, GPIO expander) via shared data bus. IC Role / Device Role / Timing Role: Acts as address-select multiplexer; asserts unique /CS per peripheral based on address decode, isolating bus contention. Use Value: Ensures only one peripheral responds per transaction; prevents signal collisions without software overhead or additional arbitration logic. |
| LED Segment Enable Control | Legacy Bus Interface Logic |
|
Use Scenario: Driving common-anode 7-segment displays in multiplexed digital panel meters or instrumentation front-ends. IC Role / Device Role / Timing Role: Provides four active-low digit enables synchronized to display refresh cycle; paired with BCD-to-7-segment drivers. Use Value: Delivers precise, glitch-free digit strobing; 8 mA sink capability directly drives LED cathodes without external transistors. |
Use Scenario: Interfacing 8-bit microcontrollers to older TTL peripheral ICs (e.g., 74LS244, 74LS373) requiring decoded control signals. IC Role / Device Role / Timing Role: Generates /RD, /WR, /IOR, /IOW equivalents from address and control bus; maintains LS-TTL timing alignment. Use Value: Preserves setup/hold timing margins across bus transactions; avoids metastability in asynchronous peripheral handshaking. |
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 |
|---|---|---|---|
| SN74LS139AN | Same logic function and electrical specs, but in 16-pin PDIP package; no RoHS compliance; 25-piece tube packaging. | Preferred for through-hole prototyping, lab validation, or repair of legacy through-hole PCBs where SOP rework is impractical. | Select SN74LS139AN only when board layout lacks SOP footprint or manual soldering is required; not suitable for automated SMT production. |
| SN74LS139ADR | Identical function and specs, SOIC (D) package; same RoHS/NiPdAu finish and MSL Level-1 rating, but 2500-piece tape-and-reel quantity. | Better suited for high-volume SMT lines due to larger reel size and identical thermal/mechanical profile to SN74LS139ANSR. | Choose SN74LS139ADR for production runs >5k units; SN74LS139ANSR remains optimal for mid-volume or mixed-technology builds. |
Compared with SN74LS139AN (PDIP) and SN74LS139ADR (SOIC-D), the SN74LS139ANSR offers identical logic behavior and timing in a cost-optimized SOP-NS package with industry-standard 2000-unit reels-making it the preferred choice for new SMT designs requiring legacy TTL compatibility without over-spec'ing reel size or sacrificing RoHS compliance.
Availability
SN74LS139ANSR is available at Aetrix Electronics and suitable for memory decoding, I/O expansion, LED multiplexing, and legacy bus interfacing requiring stable component supply across industrial control, test equipment, and retro-computing restoration programs.
Supply support for SN74LS139ANSR 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 founded in 1930, specializing in analog, embedded processing, and logic solutions with broad industrial, automotive, and consumer reach.
The SN74LS139ANSR belongs to TI's legacy 74LS logic family product line, engineered specifically for backward compatibility with 1970s–1990s TTL-based digital systems while maintaining manufacturability and long-term supply assurance.
FAQ
What is the maximum clock frequency supported by the SN74LS139ANSR?
The SN74LS139ANSR is not a clocked device-it has no internal clock and operates asynchronously. Its usable switching rate is limited by propagation delay (25 ns max) and system-level setup/hold timing. In practice, it reliably supports address decode operations up to ~20 MHz in well-designed TTL buses, but timing must be verified against the full path including driver rise time and capacitive loading.
Can SN74LS139ANSR drive LEDs directly?
Yes, the SN74LS139ANSR can drive common-anode LEDs directly: each active-low output sinks up to 8 mA, sufficient for indicator LEDs with appropriate current-limiting resistors (e.g., 330 Ω @ 5 V). Do not exceed IOL = 8 mA per output or 50 mA total device sink current to maintain output voltage compliance and avoid thermal stress.
Is SN74LS139ANSR pin-compatible with SN74LS139AN?
Yes, SN74LS139ANSR and SN74LS139AN share identical pinout and logic function-both are 16-pin dual 2-to-4 decoders with the same terminal assignments. However, SN74LS139ANSR uses SOP (NS) packaging while SN74LS139AN uses PDIP (N); physical mounting differs, but schematic symbol and netlist mapping are interchangeable.
Does SN74LS139ANSR support mixed-voltage operation (e.g., 3.3 V inputs)?
No, SN74LS139ANSR is strictly a 5 V LS-TTL device. Its input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) are incompatible with 3.3 V logic families: a 3.3 V high signal may not register as valid logic high, causing unreliable decoding. Use a level translator (e.g., SN74LVC1T45) if interfacing with 3.3 V controllers.
What is the recommended bypass capacitor for SN74LS139ANSR?
A 0.1 µF ceramic capacitor placed as close as possible to the VCC (pin 13) and GND (pin 8) terminals is recommended for SN74LS139ANSR. This suppresses high-frequency switching noise generated during output transitions and prevents supply rail droop that could affect adjacent TTL devices sharing the same 5 V rail.
SN74LS139ANSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.209", 5.30mm 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:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
SN74LS139ANSR FAQ
1.How can I place an order for SN74LS139ANSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS139ANSR 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 SN74LS139ANSR reliable?
The price and inventory of SN74LS139ANSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS139ANSR is usually 5 days.
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SN74LS139ANSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS139ANSR 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 SN74LS139ANSR?
For technical support, including SN74LS139ANSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS139ANSR requirements.
6.How does Aetrix verify that SN74LS139ANSR is sourced from the original manufacturer or authorized distributors?
All SN74LS139ANSR 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 SN74LS139ANSR meets industry standards.
7.What is the process for return or replacement of SN74LS139ANSR?
All SN74LS139ANSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS139ANSR, 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 SN74LS139ANSR part is unused and in its original packaging.
Return procedure for SN74LS139ANSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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