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Texas Instruments SN74LS251NG4
- Part No.:
- SN74LS251NG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74LS251NG4.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,363
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Product details
Overview
SN74LS251NG4 from Texas Instruments is a dual 4-line to 1-line data selector/multiplexer with three-state outputs, implemented in TTL logic, operating at VCC = 4.75–5.25 V, with propagation delay tpd = 22 ns (max) and fan-out of 20 LS-TTL loads, used in digital address/data routing and bus arbitration circuits.
For engineers reviewing the SN74LS251NG4 datasheet, SN74LS251NG4 pinout, SN74LS251NG4 application, or SN74LS251NG4 equivalent, this device supports 8-input selection via 3-bit address lines, enables bidirectional bus control through active-low output enable (OE̅), and delivers guaranteed noise margin of 0.4 V under standard TTL loading conditions.
Technical Context
The SN74LS251NG4 integrates eight input channels (I0–I7), three binary select inputs (S0, S1, S2), an active-low output enable (OE̅), and complementary outputs Y and Y̅. It implements standard TTL voltage thresholds: VIH = 2.0 V (min), VIL = 0.8 V (max), and drives both Y and Y̅ simultaneously with identical timing.
Its internal architecture uses discrete transistor-level logic gates to decode the 3-bit select code and gate the selected input to the output stage, which features a totem-pole output with three-state capability. Output leakage current is limited to ±10 µA when disabled, and DC output voltage levels meet TTL specifications: VOH = 2.7 V (min), VOL = 0.5 V (max) at IO = –0.4 mA / 8 mA.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Supply | 4.75 V to 5.25 V - ensures compatibility with standard TTL power rails and stable operation across industrial voltage tolerances. |
| Propagation Delay | 22 ns (max) - defines worst-case signal routing latency for synchronous bus switching and address decoding timing budgets. |
| Output Drive | –0.4 mA (source), 8 mA (sink) - supports direct interfacing with LS-TTL inputs without external pull-ups or buffers. |
| Noise Margin | 0.4 V (min) - guarantees reliable logic-level discrimination in electrically noisy industrial control environments. |
| Operating Temperature | 0 °C to +70 °C - validated for commercial-grade embedded systems including instrumentation and legacy computing peripherals. |
| Input Loading | 1 LS-TTL unit load per input - allows up to 20 inputs to be driven by a single output without signal degradation. |
Pinout & Package
SN74LS251NG4 is supplied in a 16-pin plastic dual in-line package (PDIP-N), with 0.3-inch body width, 0.1-inch lead pitch, and through-hole mounting compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Y) | True Output | Active-high selected data output; three-state when OE̅ = HIGH. |
| 2 (I0) | Data Input 0 | Low-order input channel selected when S2S1S0 = 000. |
| 3 (I1) | Data Input 1 | Input channel selected when S2S1S0 = 001. |
| 4 (I2) | Data Input 2 | Input channel selected when S2S1S0 = 010. |
| 5 (I3) | Data Input 3 | Input channel selected when S2S1S0 = 011. |
| 6 (I4) | Data Input 4 | Input channel selected when S2S1S0 = 100. |
| 7 (I5) | Data Input 5 | Input channel selected when S2S1S0 = 101. |
| 8 (GND) | Ground Reference | Signal and power return path; must be low-impedance for TTL noise immunity. |
| 9 (I6) | Data Input 6 | Input channel selected when S2S1S0 = 110. |
| 10 (I7) | Data Input 7 | High-order input channel selected when S2S1S0 = 111. |
| 11 (S0) | Select Bit 0 | Least-significant address bit controlling input selection. |
| 12 (S1) | Select Bit 1 | Middle-significance address bit for 3-bit decode. |
| 13 (S2) | Select Bit 2 | Most-significant address bit completing 8:1 selection. |
| 14 (OE̅) | Output Enable (active low) | Disables Y and Y̅ outputs to high-impedance state when HIGH. |
| 15 (Y̅) | Inverted Output | Complementary true output; mirrors Y with identical timing and drive strength. |
| 16 (VCC) | Positive Supply | +5 V power rail connection; requires local 0.1 µF bypass capacitor. |
Key Features
| Feature | Design Value |
|---|---|
| Three-State Outputs | Enables direct connection to shared data buses without external bus transceivers or isolation logic. |
| Complementary Outputs (Y/Y̅) | Provides simultaneous true and inverted signals for differential sensing or dual-rail logic interfaces. |
| Standard TTL Compatibility | Accepts and drives LS-TTL, S-TTL, and original TTL families without level-shifting circuitry. |
| Low Power Consumption | Typical ICC = 24 mA at VCC = 5 V - reduces thermal load in dense logic arrays and legacy backplanes. |
| Guaranteed AC/DC Performance | Specified over full commercial temperature range with no derating required for timing or voltage margins. |
Applications
| Microprocessor Address Decoding | Legacy Bus Arbitration |
|---|---|
|
Use Scenario: Selecting memory-mapped peripheral registers in 8-bit microprocessor systems such as Z80 or 8085-based designs. IC Role / Device Role / Timing Role: Acts as address-space decoder, routing I/O read/write strobes to specific peripheral chips based on A2–A0 address bits. Use Value: Eliminates need for discrete AND/OR gate networks, reducing board area and propagation skew in critical timing paths. |
Use Scenario: Managing shared data bus access among multiple controllers in industrial PLC backplanes. IC Role / Device Role / Timing Role: Functions as priority-controlled bus multiplexer, enabling one master to assert control while others tri-state their drivers. Use Value: Provides deterministic bus ownership handoff with sub-25 ns switching, preventing bus contention faults. |
| Digital Signal Routing | Test Equipment Multiplexing |
|
Use Scenario: Switching between multiple sensor inputs (e.g., thermocouples, RTDs) into a single ADC channel in data acquisition modules. IC Role / Device Role / Timing Role: Serves as analog front-end signal selector, synchronized to ADC conversion start pulses via OE̅ control. Use Value: Maintains signal integrity with <0.5 V output low and >2.7 V output high under full load, minimizing quantization error. |
Use Scenario: Configuring stimulus/response paths in automated test equipment (ATE) for IC functional verification. IC Role / Device Role / Timing Role: Routes pattern generator outputs to DUT pins and captures responses via Y/Y̅ dual outputs for pass/fail comparison. Use Value: Enables real-time pass/fail decision logic using complementary outputs without additional XOR gates. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8:1 multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS151N | Identical pinout, function, and AC/DC specs; differs only in part marking and packaging suffix (no G4 suffix). | No functional difference; SN74LS151N is the base catalog version without green-compliance designation. | Select SN74LS151N if RoHS exemption or legacy procurement tracking is required; otherwise SN74LS251NG4 preferred for modern compliance. |
| SN74HC251N | CMOS implementation: VCC = 2–6 V, tpd = 20 ns (typ), ICC = 8 µA (max); incompatible TTL input thresholds. | Requires level-shifting when interfacing with legacy TTL systems; unsuitable for direct replacement in 5-V-only designs. | Choose SN74HC251N only in new low-power, mixed-voltage designs where supply flexibility and static current matter more than TTL compatibility. |
Compared with SN74LS151N, SN74LS251NG4 adds RoHS-compliant finish and updated traceability marking, while SN74HC251N trades TTL interoperability for wide-supply operation and micropower standby - making SN74LS251NG4 the sole drop-in solution for maintaining legacy TTL bus integrity.
Availability
SN74LS251NG4 is available at Aetrix Electronics and suitable for microprocessor address decoding, legacy bus arbitration, digital signal routing, and test equipment multiplexing requiring stable component supply across long-lifecycle industrial programs.
Supply support for SN74LS251NG4 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 solutions for industrial, automotive, and communications markets.
The SN74LS251NG4 belongs to TI's legacy 74LS logic family, designed specifically for robust, low-cost digital control and data routing in commercial-grade systems where TTL compatibility and predictable timing are essential.
FAQ
What is the function of the SN74LS251NG4?
The SN74LS251NG4 is an 8-line to 1-line data selector/multiplexer with three-state outputs and complementary Y/Y̅ outputs. It routes one of eight digital inputs (I0–I7) to the output based on a 3-bit binary address (S2, S1, S0), and disables both outputs when OE̅ is high. This functionality makes SN74LS251NG4 ideal for bus sharing, address decoding, and signal routing in TTL-based systems.
Is SN74LS251NG4 pin-compatible with SN74LS151N?
Yes, SN74LS251NG4 is fully pin-compatible and functionally identical to SN74LS151N, sharing the same PDIP-16 footprint, pin assignments, electrical specifications, and timing behavior. The "G4" suffix denotes RoHS-compliant finish and updated manufacturing traceability, but SN74LS251NG4 operates identically to SN74LS151N in all circuit implementations.
What is the maximum operating temperature for SN74LS251NG4?
The SN74LS251NG4 is rated for operation from 0 °C to +70 °C, consistent with commercial-grade TTL logic. This range is validated across all AC and DC parameters in the official Texas Instruments datasheet SDLS085, and applies to the NG4 variant packaged in PDIP (N) format with NIPDAU lead finish.
Can SN74LS251NG4 drive standard LS-TTL loads directly?
Yes, SN74LS251NG4 can drive up to 20 LS-TTL unit loads per output, with guaranteed VOH ≥ 2.7 V at –0.4 mA and VOL ≤ 0.5 V at 8 mA. Its output structure meets standard TTL interface requirements, allowing direct connection to other LS-TTL devices without buffering or level translation - a key design feature of SN74LS251NG4.
Does SN74LS251NG4 support bidirectional data flow?
No, SN74LS251NG4 is a unidirectional multiplexer: data flows only from inputs (I0–I7) to outputs (Y/Y̅). It does not support reverse signal paths or bus transceiver functionality. For bidirectional operation, external control logic or dedicated transceivers must be used alongside SN74LS251NG4 in system-level design.
SN74LS251NG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Discontinued at Digi-Key
- Type:
- Multiplexer
- Circuit:
- 1 x 8:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 2.6mA, 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
SN74LS251NG4 FAQ
1.How can I place an order for SN74LS251NG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS251NG4 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 SN74LS251NG4 reliable?
The price and inventory of SN74LS251NG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS251NG4 is usually 5 days.
3.What payment methods are accepted for SN74LS251NG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS251NG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS251NG4?
SN74LS251NG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS251NG4 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 SN74LS251NG4?
For technical support, including SN74LS251NG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS251NG4 requirements.
6.How does Aetrix verify that SN74LS251NG4 is sourced from the original manufacturer or authorized distributors?
All SN74LS251NG4 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 SN74LS251NG4 meets industry standards.
7.What is the process for return or replacement of SN74LS251NG4?
All SN74LS251NG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS251NG4, 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 SN74LS251NG4 part is unused and in its original packaging.
Return procedure for SN74LS251NG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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