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Texas Instruments SN74LS156NE4
- Part No.:
- SN74LS156NE4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS156NE4.pdf
- Description:
- DUAL 2-LINE TO 4-LINE DECODERS/D
- Quantity:
- Payment:
- Shipping:
Inventory:2,611
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Product details
Overview
SN74LS156NE4 from Texas Instruments is a dual 2-line-to-4-line decoder/demultiplexer in a 16-pin PDIP package, operating over 0°C to 70°C, with TTL-compatible inputs and outputs, 16 mA output drive capability, and propagation delay of 25 ns typical at VCC = 5 V. It enables address decoding and data routing in legacy digital logic systems such as industrial control panels and retro-computing peripherals.
For engineers reviewing the SN74LS156NE4 datasheet, SN74LS156NE4 pinout, SN74LS156NE4 application, or SN74LS156NE4 equivalent, key selection considerations include its dual independent decoder structure, active-low enable and output logic, TTL-level compatibility, and through-hole PDIP-16 packaging for prototyping and repair.
Technical Context
The SN74LS156NE4 integrates two identical 2-to-4 line decoders on a single die, each with separate active-low enable (G̅) and complementary outputs (Y̅₀–Y̅₃). Each decoder accepts two binary inputs (A, B) and generates four mutually exclusive active-low decoded outputs.
It uses standard TTL bipolar transistor-transistor logic, ensuring compatibility with legacy 74LS, 74S, and 74 series families. Input thresholds are defined at VIL = 0.8 V max and VIH = 2.0 V min; output high/low voltages meet TTL specifications at IOH = –0.4 mA and IOL = 8 mA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Dual 2-line-to-4-line decoder/demultiplexer with active-low enables and outputs |
| Supply Voltage | 4.75 V to 5.25 V - ensures stable operation within standard TTL rail tolerance |
| Propagation Delay | 25 ns typical (A/B to Y̅), 30 ns max - supports synchronous logic up to ~20 MHz clock domains |
| Output Drive | 16 mA sink current (IOL) - directly drives multiple TTL inputs or LED indicators without buffering |
| Operating Temperature | 0°C to +70°C - suitable for commercial-grade embedded control and instrumentation |
| Package | PDIP-16 (N), lead finish NIPDAU, RoHS compliant - through-hole mount for breadboard, socket, or wave-solder assembly |
| Input Compatibility | TTL-level - interfaces directly with 74LS, 74S, 74, and microcontroller GPIO without level shifting |
Pinout & Package
SN74LS156NE4 is housed in a 16-pin plastic dual in-line package (PDIP-N) with 0.3-inch body width and 0.1-inch pin pitch, designed for through-hole mounting and manual rework.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 15 | G̅ (Enable) | Active-low enable per decoder - must be low to activate corresponding decoder outputs |
| 2, 3, 5, 6 | A, B (Inputs) | Binary address inputs for each decoder - determine which of four outputs goes low |
| 4, 7, 12, 14 | Y̅₀–Y̅₃ (Outputs) | Active-low decoded outputs - only one low per enabled decoder, based on A/B state |
| 8 | GND | Ground reference for all logic and power connections |
| 16 | VCC | +5 V supply - powers internal TTL circuitry and defines logic thresholds |
| 9–11, 13 | No Connect / Unused | Not internally bonded - left unconnected; no electrical function or thermal impact |
Key Features
| Feature | Design Value |
|---|---|
| Dual independent decoders | Two fully isolated 2-to-4 decoders share only VCC and GND - enables parallel address decoding without inter-channel coupling |
| Active-low enable & outputs | Minimizes external inversion for common bus-enable and chip-select applications using open-collector or wired-AND logic |
| TTL-compatible interface | Direct connection to legacy 74-series logic, microcontrollers, and peripheral ICs without level-shifting circuitry |
| High noise immunity | Input hysteresis and defined VIL/VIH thresholds reject >0.4 V of ground bounce or supply ripple |
| Through-hole PDIP packaging | Facilitates hand-soldering, socket-based testing, and long-term field serviceability in industrial equipment |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
Use Scenario: Selecting one of four RAM or ROM chips in an 8-bit microcomputer system using upper address bits. IC Role / Device Role / Timing Role: SN74LS156NE4 acts as a dual address decoder, mapping A15–A14 to chip-enable lines for four memory banks. Use Value: Reduces external logic count by replacing two discrete 74LS139s; maintains timing predictability with 25 ns propagation delay. | Use Scenario: Enabling UART, timer, or I/O port ICs in a Z80 or 8085-based controller board. IC Role / Device Role / Timing Role: SN74LS156NE4 provides active-low peripheral select signals synchronized to address decode cycle. Use Value: Eliminates need for discrete inverters when interfacing with devices requiring low-active chip selects. |
| LED Segment Driver Control | Legacy Bus Arbitration |
Use Scenario: Driving common-cathode 7-segment displays via multiplexed digit selection in test equipment front panels. IC Role / Device Role / Timing Role: SN74LS156NE4 selects one of four display digits using decoded scan lines. Use Value: Leverages 16 mA sink capability to drive segments directly without external transistors. | Use Scenario: Managing access priority among four DMA channels or interrupt request lines in vintage minicomputer backplanes. IC Role / Device Role / Timing Role: SN74LS156NE4 generates mutually exclusive grant signals based on encoded bus request lines. Use Value: Ensures deterministic arbitration with no race conditions due to fixed propagation delay and monotonic output behavior. |
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 |
|---|---|---|---|
| SN74LS139N | Single-package dual 2-to-4 decoder with identical pinout and logic, but includes internal input inverters and active-low outputs only - no enable polarity difference. | Same functional coverage; used interchangeably where enable polarity matches system design. | Select SN74LS139N if board layout already accommodates its identical footprint and system logic uses inverted enables. |
| SN74HC139N | CMOS version with higher noise margin (VIH = 3.15 V min), lower ICC, but requires 2–6 V supply and has slower edge rates - not TTL-compatible without level adaptation. | Suitable for mixed-voltage or low-power upgrades; incompatible with pure TTL buses without interface buffers. | Choose SN74HC139N only when redesigning for CMOS supply rails and noise resilience, not for drop-in replacement. |
Compared with SN74LS156NE4, SN74LS139N offers identical pinout and TTL compatibility for seamless substitution, while SN74HC139N trades TTL interoperability for CMOS efficiency and voltage flexibility - making the former ideal for repair, the latter for new low-power designs.
Availability
SN74LS156NE4 is available at Aetrix Electronics and suitable for industrial control panels, retro-computing restoration, and legacy test equipment requiring stable component supply and long-term obsolescence support.
Supply support for SN74LS156NE4 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 and automotive qualification.
The SN74LS156NE4 belongs to TI's legacy 74LS logic family, designed specifically for reliable, pin-compatible replacement of earlier 74-series TTL components in commercial-grade digital systems.
FAQ
What is the logic configuration of the SN74LS156NE4?
The SN74LS156NE4 contains two independent 2-line-to-4-line decoders, each with active-low enable (G̅) and active-low outputs (Y̅₀–Y̅₃). Inputs A and B select one of four outputs to go low when G̅ is asserted; all other outputs remain high. This configuration supports chip-select, address decode, and demultiplexing functions without external inversion.
Can SN74LS156NE4 be used as a demultiplexer?
Yes, the SN74LS156NE4 can function as a dual 1-to-4 demultiplexer. When data is applied to the enable input (G̅) and address bits to A/B, the selected output mirrors the inverted enable state. Since outputs are active-low, applying a low signal to G̅ routes it to one of four destinations based on A/B, satisfying basic demux functionality in TTL systems.
Is SN74LS156NE4 pin-compatible with SN74LS139N?
No, SN74LS156NE4 is not pin-compatible with SN74LS139N. Although both are dual 2-to-4 decoders, SN74LS156NE4 uses pins 1 and 15 as separate enables and has unused pins (9–11, 13), whereas SN74LS139N assigns enables to pins 1 and 14 and uses all 16 pins functionally. Board-level substitution requires layout modification.
What is the maximum clock frequency supported by SN74LS156NE4?
The SN74LS156NE4 does not operate on a clock signal - it is combinational logic. Its usable switching rate is determined by propagation delay: 25 ns typical (A/B to Y̅), allowing reliable operation in synchronous systems with minimum pulse widths ≥50 ns. For repetitive address decode, this supports effective rates up to ~20 MHz under ideal loading.
Does SN74LS156NE4 support mixed-voltage operation?
No, SN74LS156NE4 is specified only for 5 V ±5% (4.75 V to 5.25 V) operation. It is a TTL-family device with bipolar input structure and fixed threshold voltages; operation outside this range risks incorrect logic states, excessive power dissipation, or permanent damage. It is not compatible with 3.3 V or other supply rails without level translation.
SN74LS156NE4 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:
- 2 x 2:4
- Independent Circuits:
- 1
- Current - Output High, Low:
- -, 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
SN74LS156NE4 FAQ
1.How can I place an order for SN74LS156NE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS156NE4 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 SN74LS156NE4 reliable?
The price and inventory of SN74LS156NE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS156NE4 is usually 5 days.
3.What payment methods are accepted for SN74LS156NE4?
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4.How is shipping managed for SN74LS156NE4?
SN74LS156NE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS156NE4 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 SN74LS156NE4?
For technical support, including SN74LS156NE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS156NE4 requirements.
6.How does Aetrix verify that SN74LS156NE4 is sourced from the original manufacturer or authorized distributors?
All SN74LS156NE4 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 SN74LS156NE4 meets industry standards.
7.What is the process for return or replacement of SN74LS156NE4?
All SN74LS156NE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS156NE4, 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 SN74LS156NE4 part is unused and in its original packaging.
Return procedure for SN74LS156NE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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