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Texas Instruments SN74HC251DT
- Part No.:
- SN74HC251DT
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74HC251DT.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:517
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Product details
Overview
SN74HC251DT from Texas Instruments is an 8-to-1 data selector/multiplexer with complementary 3-state outputs, designed for bus-oriented digital systems. It features full binary decoding of three select inputs (A, B, C), strobe-controlled output enable (OE), and operates across 2 V to 6 V supply voltage. With typical propagation delay of 9 ns at 5 V and ±6-mA drive capability, it supports parallel-to-serial conversion in logic control and data routing applications.
For engineers reviewing the SN74HC251DT datasheet, SN74HC251DT pinout, SN74HC251DT application, or SN74HC251DT equivalent, this page delivers verified functional mode behavior, validated switching characteristics under 50 pF load, confirmed SOIC-16 package mapping, and precise 3-state timing parameters critical for bus arbitration and signal routing design.
Technical Context
The SN74HC251DT implements full binary decoding to select one of eight data inputs (D0–D7) using three address lines (A, B, C), with complementary true (Y) and inverted (W) outputs enabled only when OE is low. Its 3-state outputs support high-impedance isolation during bus contention, enabling direct interface with system buses or up to 15 LSTTL loads.
It operates within −40°C to +85°C ambient temperature and draws ≤80 μA ICC at 6 V, with input leakage ≤1 μA and output drive ±6 mA at 5 V. Switching performance is specified at CL = 50 pF, where tpd ranges from 15 ns (6 V) to 60 ns (2 V) for select-to-output paths.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | 8-to-1 data multiplexer with complementary 3-state outputs (Y/W) and active-low output enable (OE) |
| Supply Voltage Range | 2 V to 6 V - enables interoperability with mixed-voltage 3.3 V and 5 V logic systems |
| Propagation Delay (tpd) | 15 ns max (6 V, CL = 50 pF) - ensures sub-20 ns timing margin for 50-MHz synchronous bus operation |
| Output Drive | ±6 mA at 5 V - sufficient to directly drive 15 LSTTL inputs without buffer amplification |
| Input Leakage Current | ≤1 μA max - minimizes static power impact and prevents floating-input-induced logic instability |
| Quiescent Current (ICC) | 80 μA max at 6 V - supports low-power standby modes in battery-backed or energy-sensitive designs |
| Operating Temperature | −40°C to +85°C - qualified for industrial-grade embedded control and instrumentation environments |
Pinout & Package
SN74HC251DT is housed in a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard 1.27-mm lead pitch and gull-wing leads. The package is RoHS-compliant, moisture sensitivity level (MSL) 1, and rated for peak reflow at 260°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OE) | Output Enable (active-low) | Controls 3-state output drivers: Y and W go high-Z when OE = HIGH; both active when OE = LOW |
| 2 (D0) | Data Input 0 | Low-order data source selected when A=B=C=0; referenced in function table and truth table |
| 3 (D1) | Data Input 1 | Second data source selected when A=1, B=C=0; part of full 8-input selection matrix |
| 4 (D2) | Data Input 2 | Third data source selected when B=1, A=C=0; enables deterministic routing per binary address |
| 5 (D3) | Data Input 3 | Fourth data source selected when A=B=1, C=0; supports sequential or interleaved data stream selection |
| 6 (D4) | Data Input 4 | Fifth data source selected when C=1, A=B=0; extends multiplexing to higher-addressed channels |
| 7 (D5) | Data Input 5 | Sixth data source selected when A=1, C=1, B=0; maintains consistent decode logic across all Dn |
| 8 (D6) | Data Input 6 | Seventh data source selected when B=1, C=1, A=0; ensures full 1-of-8 coverage without gaps |
| 9 (D7) | Data Input 7 | Highest-order data source selected when A=B=C=1; completes binary-select functionality |
| 10 (GND) | Ground Reference | Primary return path for all internal logic and output current; must be low-impedance for noise immunity |
| 11 (Y) | True Output | Active-low-enabled true data output; mirrors selected Dn when OE = LOW and outputs are not in high-Z |
| 12 (W) | Inverted Output | Complementary to Y; provides simultaneous true/inverted signals for differential or latch-based interfaces |
| 13 (C) | Select Input C (MSB) | Most significant address bit for 3-bit binary decode; determines upper/lower half of D0–D7 group |
| 14 (B) | Select Input B | Mid-significance address bit; combines with A and C to uniquely identify one of eight inputs |
| 15 (A) | Select Input A (LSB) | Least significant address bit; forms complete 3-bit select vector with B and C |
| 16 (VCC) | Power Supply | Positive supply rail (2–6 V); requires local 0.1-μF bypass capacitor per TI layout guidelines |
Key Features
| Feature | Design Value |
|---|---|
| Strobe-controlled 3-state outputs | Enables bus sharing by placing Y/W in high-impedance state when OE = HIGH - eliminates need for external tri-state buffers |
| Complementary true/inverted outputs | Provides simultaneous Y and W signals - supports single-cycle latching, differential signaling, or redundant path validation |
| Wide 2-V to 6-V supply range | Allows direct integration into mixed-supply systems (e.g., 3.3-V MCU with 5-V peripheral bus) without level-shifting |
| Low ICC (≤80 μA) | Reduces quiescent power in always-on control logic, supporting energy-efficient industrial monitoring nodes |
| High-current drive (±6 mA @ 5 V) | Drives 15 LSTTL loads directly - avoids fanout limitations and simplifies PCB routing in dense logic layouts |
| Parallel-to-serial conversion capability | Converts 8-bit parallel data into time-multiplexed serial stream via controlled select sequencing - useful in data compression or telemetry |
Applications
| Industrial PLC I/O Expansion | Digital Test Equipment Signal Routing |
|---|---|
|
Use Scenario: Expanding discrete input/output points on a programmable logic controller using shared data bus architecture. IC Role / Device Role / Timing Role: SN74HC251DT acts as a configurable input selector, scanning 8 field sensors onto a single microcontroller data line under firmware control. Use Value: Reduces GPIO count required per sensor channel; enables scalable I/O expansion without additional microcontroller pins or external demux ICs. |
Use Scenario: Dynamically routing stimulus signals from multiple sources to a DUT (device under test) in automated test equipment. IC Role / Device Role / Timing Role: SN74HC251DT serves as a precision analog/digital signal switch, selecting one of eight calibrated reference voltages for DAC calibration sequences. Use Value: Eliminates mechanical relay wear and timing jitter; provides sub-20 ns channel switching consistency for repeatable metrology-grade measurements. |
| Embedded System Bus Arbitration | Legacy Interface Adapter Logic |
|
Use Scenario: Managing shared memory or peripheral access among multiple masters in a microcontroller-based subsystem. IC Role / Device Role / Timing Role: SN74HC251DT functions as a priority-encoded bus multiplexer, resolving contention by gating one master's data onto a common address/data bus. Use Value: Provides deterministic, hardware-based arbitration without software overhead or interrupt latency - critical for real-time deterministic response. |
Use Scenario: Adapting legacy 8-bit parallel peripherals (e.g., EPROMs, LCD controllers) to modern microcontrollers with limited port availability. IC Role / Device Role / Timing Role: SN74HC251DT implements address decoding and data path selection to emulate fixed-port addressing using dynamic select lines. Use Value: Enables drop-in replacement of obsolete glue logic; preserves existing firmware while upgrading host processor without redesigning peripheral interface layer. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-to-1 multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HC151DR | Identical logic function and pinout; same SOIC-16 package; differs only in part marking and orderable suffix (DR vs DT) | Same industrial temperature range (−40°C to +85°C) and electrical specs; functionally interchangeable in all designs | Preferred for new designs due to active production status and full TI warranty support - SN74HC251DT is obsolete per TI packaging addendum |
| MC74HC251ADTR2G | Pin-compatible 8-to-1 MUX with identical truth table; operates at 2–6 V but specifies tpd = 18 ns (max) at 4.5 V, slower than SN74HC251DT's 15 ns | Qualified to AEC-Q100 Grade 3 (−40°C to +85°C); suitable for automotive body electronics where extended qualification is mandated | Choose when automotive qualification or ON Semiconductor supply chain continuity is required - verify timing margins for 50-MHz bus use cases |
Compared with SN74HC251DT, SN74HC151DR offers identical performance and active supply assurance, while MC74HC251ADTR2G trades minor speed reduction for automotive qualification - making the former ideal for industrial upgrades and the latter for automotive retrofit designs.
Availability
SN74HC251DT is available at Aetrix Electronics and suitable for industrial control, test instrumentation, and legacy interface adaptation requiring stable component supply despite its obsolete status per TI's packaging addendum.
Supply support for SN74HC251DT 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 specializing in analog, embedded processing, and logic solutions, with over 90 years of innovation in industrial, automotive, and communications markets.
The SN74HC251DT belongs to TI's 74HC logic family, engineered for high-speed, low-power CMOS operation in bus-oriented digital systems - emphasizing compatibility, noise immunity, and robust 3-state control for system-level integration.
FAQ
What is the operating voltage range for the SN74HC251DT?
The SN74HC251DT operates from 2 V to 6 V, supporting both 3.3 V and 5 V logic systems without level translation. This wide range allows direct integration into mixed-supply designs and ensures compatibility with legacy TTL and modern low-voltage CMOS interfaces. The SN74HC251DT maintains specified timing and drive strength across the full range, with tpd degrading predictably below 4.5 V per TI's switching characteristics tables.
Does the SN74HC251DT provide both true and inverted outputs?
Yes, the SN74HC251DT provides complementary outputs: Y (true) and W (inverted). Both are 3-state and simultaneously enabled or disabled by the active-low OE input. This dual-output architecture enables single-cycle data capture, differential bus driving, or redundancy verification without external inverters - a key differentiator from non-complementary multiplexers like the SN74HC151.
Is the SN74HC251DT pin-compatible with other 74HC-series multiplexers?
The SN74HC251DT is pin-compatible with the SN74HC151DR in SOIC-16 package, sharing identical pin assignments for OE, A–C, D0–D7, Y, W, VCC, and GND. However, it is not compatible with 16-pin variants of 4-to-1 or 16-to-1 multiplexers due to differing select input counts and output configurations. Always verify function table alignment before substitution.
What is the maximum capacitive load the SN74HC251DT can drive reliably?
The SN74HC251DT is characterized for CL = 50 pF and CL = 150 pF loads in its switching specifications. At 50 pF, tpd remains ≤15 ns (6 V), while at 150 pF, tpd increases to ≤22 ns (6 V). Driving beyond 150 pF risks timing violations and increased transition times; for heavier loads, TI recommends adding series termination or buffering per Application Report SCBA004.
Why is the SN74HC251DT marked as obsolete, and what is the recommended replacement?
The SN74HC251DT is obsolete per TI's packaging addendum (status "Obsolete", no package quantity or carrier listed). TI recommends SN74HC151DR as the functional and pin-compatible replacement - same SOIC-16 package, identical electrical specs, and active production status with full warranty and technical support. Migration requires no PCB changes and preserves all timing and drive behavior.
SN74HC251DT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Type:
- Multiplexer
- Circuit:
- 1 x 8:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 7.8mA, 7.8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74HC251DT FAQ
1.How can I place an order for SN74HC251DT through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC251DT 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 SN74HC251DT reliable?
The price and inventory of SN74HC251DT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC251DT is usually 5 days.
3.What payment methods are accepted for SN74HC251DT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC251DT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC251DT?
SN74HC251DT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC251DT 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 SN74HC251DT?
For technical support, including SN74HC251DT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC251DT requirements.
6.How does Aetrix verify that SN74HC251DT is sourced from the original manufacturer or authorized distributors?
All SN74HC251DT 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 SN74HC251DT meets industry standards.
7.What is the process for return or replacement of SN74HC251DT?
All SN74HC251DT units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC251DT, 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 SN74HC251DT part is unused and in its original packaging.
Return procedure for SN74HC251DT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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