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Texas Instruments SN74HC251NS
- Part No.:
- SN74HC251NS
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74HC251NS.pdf
- Description:
- IC DATA SELECT/MUX TRI-ST 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:9,772
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Product details
Overview
SN74HC251NS from Texas Instruments is an 8-input, 3-state CMOS multiplexer with complementary outputs (Y and Y), three binary select inputs (S0–S2), and active-low output enable (OE). It routes one of eight data inputs (I0–I7) to the outputs under logic control, supports rail-to-rail input voltage range (0 V to VCC), and operates across −40 °C to +85 °C. It is used in digital signal routing, data selector logic, and bus isolation circuits.
For engineers reviewing the SN74HC251NS datasheet, SN74HC251NS pinout, SN74HC251NS application, or SN74HC251NS equivalent, this page delivers verified functional identity, JEDEC-compliant timing specs, SO-16 package mapping, real-world use cases, and two validated alternative parts for design flexibility and supply continuity.
Technical Context
The SN74HC251NS implements a standard 8:1 multiplexer function with non-inverting data path and complementary outputs. Its select logic decodes S2:S0 as a 3-bit binary address to route the corresponding I0–I7 input to Y (true) and Y (inverted), while OE controls high-impedance tri-state behavior on both outputs.
Input clamp diodes allow safe interfacing to voltages exceeding VCC when used with current-limiting resistors. The device complies with JEDEC Std 7A, supports CMOS-level input thresholds, and features ESD protection per HBM (>2000 V) and MM (>200 V) standards.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74HC - High-speed CMOS compatible with 2–6 V VCC operation and CMOS-level input thresholds. |
| Function | 8:1 multiplexer with complementary outputs (Y/Y) and active-low 3-state output enable (OE). |
| Supply Voltage Range | 2.0 V to 6.0 V - Enables interoperability with 3.3 V and 5 V logic systems without level shifters. |
| Propagation Delay (In → Y) | 14 ns typical at VCC = 6.0 V - Supports high-speed data selection in timing-critical control paths. |
| Output Drive Strength | ±4 mA at VCC = 4.5 V - Sufficient to drive standard TTL loads or multiple 74HC inputs directly. |
| Input Clamp Diodes | Integrated - Permits safe interface to signals up to VCC + 0.5 V using external current-limiting resistors. |
| Operating Temperature | −40 °C to +85 °C - Qualified for industrial-grade embedded and instrumentation applications. |
Pinout & Package
SN74HC251NS is supplied in a 16-pin plastic small outline (SO-16) package per JEDEC MS-012, body width 3.9 mm, with standard 1.27 mm pitch and gull-wing leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 12, 13, 14, 15 | Data inputs I0–I7 | Eight independent logic inputs selected by S2:S0; all accept 0 V to VCC voltage range. |
| 5 | True output Y | Active-high multiplexer output; goes high-Z when OE = HIGH. |
| 6 | Inverted output Y | Complementary version of Y; also tri-stated synchronously with OE. |
| 7 | Output enable OE | Active-low control: LOW enables outputs; HIGH forces Y and Y into high-impedance state. |
| 8 | GND | Ground reference (0 V) for all internal circuitry and I/O pins. |
| 9, 10, 11 | Select inputs S0, S1, S2 | 3-bit binary address determining which Ix is routed to Y/Y; LSB = S0, MSB = S2. |
| 16 | VCC | Positive supply rail (2.0–6.0 V); powers internal logic and output drivers. |
Key Features
| Feature | Design Value |
|---|---|
| CMOS-level compatibility | Supports direct connection to other 74HC/74HCT devices without level translation across 2–6 V VCC. |
| Tri-state complementary outputs | Enables bidirectional bus sharing and eliminates contention when multiple SN74HC251NS devices drive common lines. |
| Input clamp diode protection | Allows robust interfacing to overvoltage sources (e.g., microcontroller GPIOs at 5 V driving 3.3 V logic) with simple series resistors. |
| JEDEC Std 7A compliance | Ensures interoperability with legacy TTL and modern CMOS systems via standardized AC/DC electrical behavior. |
| Industrial temperature range | Validated operation from −40 °C to +85 °C supports deployment in factory automation, test equipment, and outdoor electronics. |
Applications
| Industrial Data Acquisition | Digital Test Equipment |
|---|---|
|
Use Scenario: Multiplexing analog-to-digital converter (ADC) channel selection signals in multi-sensor monitoring systems. IC Role / Device Role / Timing Role: Digital selector routing discrete sensor enable lines based on microcontroller address commands. Use Value: Reduces microcontroller GPIO count by consolidating eight sensor control lines into three select lines plus one enable line. |
Use Scenario: Routing stimulus signals to DUT (Device Under Test) pins during automated functional testing. IC Role / Device Role / Timing Role: Signal path switch enabling programmable test pattern injection across 8 DUT inputs. Use Value: Achieves sub-50 ns propagation delay and precise edge alignment critical for timing-sensitive test vectors. |
| Programmable Logic Interface | Legacy Bus Isolation |
|
Use Scenario: Interfacing FPGA configuration registers to multiple peripheral control lines in reconfigurable logic designs. IC Role / Device Role / Timing Role: Address-decoded data selector translating register bits into dedicated peripheral enable signals. Use Value: Provides deterministic, glitch-free output transitions due to synchronous enable and non-inverting path. |
Use Scenario: Isolating legacy parallel bus segments (e.g., ISA or PC/104) during hot-swap or power sequencing events. IC Role / Device Role / Timing Role: Tri-state gate controlling data flow between bus master and slave modules. Use Value: Prevents bus contention during power-up/down by holding outputs in high-Z until OE is asserted. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8:1 multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT251N | TTL-compatible inputs (VIH = 2.0 V min); identical pinout and function; same SO-16 package. | Better suited for mixed 5 V TTL/CMOS systems where input noise margin must match legacy TTL levels. | Select when interfacing directly to 74LS or 74F logic without pull-ups or level shifters. |
| MC74HC251AD | Identical 74HC logic family, but offered in SOIC-16 (SOT109-1) by ON Semiconductor; same electrical specs and pinout. | No functional difference; used where second-source qualification or alternate supply chain is required. | Choose for dual-sourcing assurance or procurement flexibility without redesign or layout change. |
Compared with SN74HC251NS, SN74HCT251N offers improved noise immunity in 5 V TTL environments, while MC74HC251AD provides a fully compatible second-source option-both preserve timing, drive strength, and PCB footprint.
Availability
SN74HC251NS is available at Aetrix Electronics and suitable for industrial control, test instrumentation, programmable logic interfaces, and legacy bus isolation requiring stable component supply and long-term production support.
Supply support for SN74HC251NS 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 ICs, with decades of heritage in industry-standard logic families.
The SN74HC251NS belongs to TI's 74HC logic portfolio, designed for low-power, high-noise-immunity digital signal routing in industrial, instrumentation, and computing applications.
FAQ
What is the supply voltage range for SN74HC251NS?
The SN74HC251NS operates from 2.0 V to 6.0 V. This wide VCC range allows direct integration into both 3.3 V and 5 V systems without level-shifting circuitry. At VCC = 2.0 V, it maintains full functionality with propagation delays up to 255 ns; at VCC = 6.0 V, typical tpd drops to 14 ns. The device draws <160 µA ICC across its full temperature range.
Does SN74HC251NS support tri-state operation on both outputs?
Yes, SN74HC251NS provides true 3-state operation on both Y and Y outputs. When OE is HIGH, both outputs enter high-impedance (Z) state simultaneously, regardless of select or input states. This behavior is confirmed in the function table (Table 3) and supported by the pin description stating "output enable input (active LOW)" for Pin 7.
Can SN74HC251NS interface safely with signals above VCC?
Yes - SN74HC251NS includes integrated input clamp diodes on all inputs (I0–I7, S0–S2, OE). When driven with voltages up to VCC + 0.5 V, these diodes conduct excess current to VCC or GND, provided external current-limiting resistors are used per datasheet guidance. This enables safe interfacing with higher-voltage controllers or sensors.
What is the maximum operating temperature for SN74HC251NS?
The SN74HC251NS is rated for operation from −40 °C to +85 °C. This industrial temperature grade is explicitly specified in Table 5 (Recommended Operating Conditions) and validated across static and dynamic characteristics in Tables 6 and 7. It is not qualified for automotive (−40 °C to +125 °C) use.
Is SN74HC251NS pin-compatible with SN74HCT251N?
Yes - SN74HC251NS and SN74HCT251N share identical pin configuration, package (SO-16), and functional block diagram. Both use Pins 1–4 and 12–15 for I0–I7, Pin 5 for Y, Pin 6 for Y, Pin 7 for OE, Pins 9–11 for S0–S2, Pin 8 for GND, and Pin 16 for VCC. Only input threshold levels differ (CMOS vs. TTL), making them drop-in replacements in most 5 V systems.
SN74HC251NS Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-SOIC (0.209", 5.30mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- 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-SO
SN74HC251NS FAQ
1.How can I place an order for SN74HC251NS through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC251NS 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 SN74HC251NS reliable?
The price and inventory of SN74HC251NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC251NS is usually 5 days.
3.What payment methods are accepted for SN74HC251NS?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC251NS transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC251NS?
SN74HC251NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC251NS 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 SN74HC251NS?
For technical support, including SN74HC251NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC251NS requirements.
6.How does Aetrix verify that SN74HC251NS is sourced from the original manufacturer or authorized distributors?
All SN74HC251NS 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 SN74HC251NS meets industry standards.
7.What is the process for return or replacement of SN74HC251NS?
All SN74HC251NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC251NS, 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 SN74HC251NS part is unused and in its original packaging.
Return procedure for SN74HC251NS:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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