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Texas Instruments SN74F251BD
- Part No.:
- SN74F251BD
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74F251BD.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,162
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Product details
Overview
SN74F251BD from Texas Instruments is an 8-line-to-1-line data selector/multiplexer with 3-state complementary outputs (Y and W), binary address decoding (A, B, C), strobe-controlled enable (G), and operation over 0°C to 70°C at VCC = 4.5–5.5 V. It performs parallel-to-serial data routing in bus-organized systems and supports true/inverted output delivery.
For engineers reviewing the SN74F251BD datasheet, SN74F251BD pinout, SN74F251BD application, or SN74F251BD equivalent, this device is selected for TTL-compatible data path control where low propagation delay (<12.5 ns), high-output drive (24 mA sink), and bus-isolation capability are required in legacy industrial logic designs.
Technical Context
The SN74F251BD implements full binary decoding of three select inputs (A, B, C) to route one of eight data inputs (D0–D7) to complementary 3-state outputs Y and W. Strobe input G controls output enable: when high, both outputs enter high-impedance state, decoupling the device from the bus.
Its logic diagram confirms totem-pole output structure with dual-transistor drivers per output, and absolute maximum ratings specify −0.5 V to 7 V supply range, −1.2 V to 7 V input voltage tolerance, and 48 mA low-level output current capability - consistent with F-series TTL performance envelopes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V TTL power rails and noise margin stability |
| tPHL (max) | 9 ns (Y output, D→Y) - enables sub-10 ns data selection critical for synchronous bus timing in 20+ MHz systems |
| IOL | 24 mA - drives heavy capacitive loads or multiple TTL inputs without external buffering |
| Output Type | 3-state complementary (Y/W) - allows bidirectional bus sharing and eliminates need for external bus transceivers |
| Operating Temp | 0°C to 70°C - qualified for commercial-grade embedded control and instrumentation applications |
| Input Thresholds | VIL ≤ 0.8 V, VIH ≥ 2.0 V - provides robust noise immunity against typical TTL-level signal degradation |
| Package | SOIC-16 (D package) - surface-mount footprint compatible with automated assembly and space-constrained PCB layouts |
Pinout & Package
SN74F251BD is housed in a 16-pin SOIC (Small-Outline Integrated Circuit) package with 1.27 mm pitch, JEDEC MS-012AC compliant outline, and moisture sensitivity level (MSL) Level-1 (unlimited floor life at ≤30°C/60% RH).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (D3) | Data input 3 | Selectable source for 3-bit binary address 011; routed to Y/W when A=1,B=1,C=0 |
| 2 (D2) | Data input 2 | Selectable source for binary address 010; active during A=1,B=0,C=0 |
| 3 (D1) | Data input 1 | Selectable source for binary address 001; used in low-order data routing |
| 4 (D0) | Data input 0 | Least-significant data source; selected when A=B=C=0 |
| 5 (Y) | True output | Active-high 3-state output delivering selected Dn value; drives bus when G=LOW |
| 6 (W) | Inverted output | Complementary to Y; provides simultaneous true/inverted logic for differential sensing or latch interfaces |
| 7 (G) | Strobe / Output enable | Active-low enable: G=HIGH forces Y/W into high-Z; essential for bus arbitration |
| 8 (GND) | Ground reference | Power return path for all internal logic and output drivers; must be low-impedance |
| 9 (VCC) | Supply voltage | +5 V nominal rail; powers all internal gates and totem-pole output stages |
| 10 (D4) | Data input 4 | Selectable source for binary address 100; routes D4 to Y/W when A=0,B=0,C=1 |
| 11 (D5) | Data input 5 | Selectable source for binary address 101; used in mid-range data selection |
| 12 (D6) | Data input 6 | Selectable source for binary address 110; supports upper-half data channeling |
| 13 (D7) | Data input 7 | Most-significant data source; selected when A=B=C=1 |
| 14 (A) | Select line A | LSB of 3-bit address bus; determines D0/D1/D2/D3 vs D4/D5/D6/D7 group selection |
| 15 (B) | Select line B | Middle bit of address; combines with A/C to uniquely decode one of eight inputs |
| 16 (C) | Select line C | MSB of address; primary determinant of upper/lower half selection |
Key Features
| Feature | Design Value |
|---|---|
| 3-State Complementary Outputs | Y and W outputs simultaneously provide true and inverted signals while enabling bus isolation via G control |
| Full Binary Decoding | Internal logic directly maps A/B/C inputs to exact D0–D7 selection without external address decoding logic |
| Bus-Compatible Drive Strength | 24 mA sink current supports direct connection to standard TTL loads without buffer amplification |
| Low Propagation Delay | Max 9 ns tPHL (D→Y) ensures tight timing alignment in high-speed data multiplexing paths |
| TTL-Compatible Input Thresholds | VIH ≥ 2.0 V and VIL ≤ 0.8 V guarantee interoperability with legacy 74-series and microcontroller GPIOs |
Applications
| Industrial PLC I/O Expansion | Legacy Microprocessor Data Bus Multiplexing |
|---|---|
Use Scenario: Expanding discrete input monitoring in programmable logic controllers using shared data bus architecture. IC Role / Device Role / Timing Role: SN74F251BD selects among eight field sensor inputs and presents them sequentially to the CPU data bus under address control. Use Value: Eliminates need for dedicated I/O port lines by time-multiplexing sensor readings onto existing 8-bit data bus with <10 ns switching latency. | Use Scenario: Routing memory-mapped peripheral registers to Z80 or 8085 CPU data bus during instruction fetch cycles. IC Role / Device Role / Timing Role: SN74F251BD acts as address-decoded data switch, selecting one of eight peripheral register banks based on A/B/C address bits. Use Value: Enables compact peripheral addressing scheme with hardware-level bus arbitration via G-strobe synchronization. |
| Test Equipment Signal Routing | Digital Logic Analyzer Channel Selection |
Use Scenario: Configurable signal path selection in automated test equipment for routing DUT outputs to measurement subsystems. IC Role / Device Role / Timing Role: SN74F251BD serves as front-end multiplexer, directing up to eight DUT signals to a single ADC or comparator input. Use Value: Provides deterministic, low-jitter signal routing with guaranteed 24 mA drive to maintain signal integrity across PCB traces. | Use Scenario: Dynamic channel assignment in portable logic analyzers with limited capture depth per channel. IC Role / Device Role / Timing Role: SN74F251BD selects which of eight probe inputs feeds the analyzer's sampling latch under microcontroller command. Use Value: Delivers sub-10 ns channel switching with complementary outputs supporting both active-high and active-low trigger detection modes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar data selector/multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS251N | Lower drive (8 mA IOL), higher tPHL (25 ns max), same pinout and function | Suitable only for low-speed, low-load applications; not recommended for bus-driving roles | Choose SN74F251BD when >20 mA sink current or <12 ns propagation is required |
| SN74HC251DR | CMOS technology, wider VCC (2–6 V), lower IOL (4 mA), no 3-state W output | Requires level-shifting for TTL bus interfacing; lacks inverted output for differential capture | Prefer SN74F251BD for direct TTL bus integration and true/inverted dual-output capability |
Compared with SN74LS251N and SN74HC251DR, the SN74F251BD delivers superior bus-drive strength and faster switching - making it the only option among the three that meets both 24 mA sink and complementary 3-state output requirements in legacy 5 V TTL systems.
Availability
SN74F251BD is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy microprocessor data bus multiplexing, and test equipment signal routing requiring stable component supply and long-term obsolescence management.
Supply support for SN74F251BD 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 SN74F251BD belongs to TI's 74F (Fast TTL) logic family, engineered for high-speed digital systems requiring improved speed-power tradeoffs over standard 74LS devices while maintaining pin compatibility and electrical interoperability.
FAQ
What is the operating temperature range specified for the SN74F251BD?
The SN74F251BD is characterized for operation from 0°C to 70°C, meeting commercial-grade environmental requirements. This range is explicitly defined in the recommended operating conditions table of the SDFS066A datasheet and applies to the D-package variant. The SN74F251BD does not support extended or military temperature ranges - those are reserved for the SN54F251B variant.
Does the SN74F251BD support true and inverted outputs simultaneously?
Yes, the SN74F251BD provides complementary outputs Y (true) and W (inverted) that reflect the selected data input Dn in real time. Both outputs are 3-state controlled by the same strobe input G, and their simultaneous availability enables direct interface with latches, comparators, or differential receivers without external inverters - a key feature confirmed in the function table and logic diagram of the SN74F251BD datasheet.
What is the maximum output sink current rating for the SN74F251BD?
The SN74F251BD is rated for 24 mA low-level output current (IOL) under recommended operating conditions (VCC = 4.5 V, TA = 0°C to 70°C). This specification is documented in the "recommended operating conditions" table and verified in the "electrical characteristics" section of the SDFS066A datasheet, confirming its ability to drive multiple TTL inputs or moderate capacitive loads directly.
Is the SN74F251BD pin-compatible with the SN74LS251N?
Yes, the SN74F251BD and SN74LS251N share identical pin assignments, function tables, and logic symbols - both use the same 16-pin DIP or SOIC footprint and implement identical 8-to-1 multiplexing with strobe-enabled 3-state outputs. However, SN74F251BD offers faster propagation (≤12.5 ns vs. ≤25 ns) and higher drive strength (24 mA vs. 8 mA), so direct substitution is electrically valid but may require timing validation in high-speed designs.
What package type is used for the SN74F251BD orderable part number?
The SN74F251BD is supplied in a 16-pin SOIC (Small-Outline Integrated Circuit) package, designated as "D" in TI's packaging nomenclature. This surface-mount package has 1.27 mm lead pitch, conforms to JEDEC MS-012AC, and is RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating - as confirmed in TI's official packaging addendum for SN74F251BD.
SN74F251BD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74F
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- Multiplexer
- Circuit:
- 1 x 8:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 3mA, 24mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74F251BD FAQ
1.How can I place an order for SN74F251BD through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74F251BD 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 SN74F251BD reliable?
The price and inventory of SN74F251BD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74F251BD is usually 5 days.
3.What payment methods are accepted for SN74F251BD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74F251BD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74F251BD?
SN74F251BD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74F251BD 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 SN74F251BD?
For technical support, including SN74F251BD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74F251BD requirements.
6.How does Aetrix verify that SN74F251BD is sourced from the original manufacturer or authorized distributors?
All SN74F251BD 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 SN74F251BD meets industry standards.
7.What is the process for return or replacement of SN74F251BD?
All SN74F251BD units undergo pre-shipment inspection (PSI). If there is an issue with SN74F251BD, 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 SN74F251BD part is unused and in its original packaging.
Return procedure for SN74F251BD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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