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Texas Instruments SN74HC251PW
- Part No.:
- SN74HC251PW
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
SN74HC251PW.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:5,444
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Product details
Overview
SN74HC251PW from Texas Instruments is an 8-to-1 data selector/multiplexer with complementary 3-state outputs, designed for bus-oriented digital systems. It operates across 2 V to 6 V, delivers ±6 mA output drive at 5 V, exhibits typical propagation delay of 9 ns (VCC = 4.5 V, CL = 50 pF), and supports parallel-to-serial conversion in microcontroller I/O expansion and address decoding applications.
For engineers reviewing the SN74HC251PW datasheet, SN74HC251PW pinout, SN74HC251PW application, or SN74HC251PW equivalent, key selection criteria include its TSSOP-16 package footprint, strobe-controlled 3-state output enable logic, true/inverted complementary outputs, and compatibility with LSTTL loads without level-shifting circuitry.
Technical Context
The SN74HC251PW implements full binary decoding of three select inputs (A, B, C) to route one of eight data inputs (D0–D7) to complementary outputs Y and W. Its 3-state outputs are jointly controlled by a single active-low output-enable (OE) input, enabling direct bus interfacing with high-impedance isolation when disabled.
It features CMOS logic architecture with TTL-compatible input thresholds, low input current (≤1 μA), and robust noise immunity-verified by VIH/VIL specifications across 2 V, 4.5 V, and 6 V supply rails. Switching performance is characterized at CL = 50 pF and CL = 150 pF, with tpd ranging from 15 ns to 51 ns depending on VCC and load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | 8-to-1 data multiplexer with complementary 3-state outputs (Y and W) |
| Supply Voltage Range | 2 V to 6 V - supports mixed-voltage system integration and battery-powered logic |
| Propagation Delay (tpd) | 19 ns typ @ VCC = 6 V, CL = 50 pF - enables timing-critical signal routing in high-speed control logic |
| Output Drive | ±6 mA @ 5 V - directly drives up to 15 LSTTL loads without external buffers |
| Input Current | ≤1 μA max - minimizes loading on upstream logic and preserves fan-out margin |
| Power Consumption (ICC) | 80 μA max @ VCC = 6 V - suitable for low-quiescent-power portable and standby-mode circuits |
| Operating Temperature | −40 °C to +85 °C - qualified for industrial-grade embedded control environments |
Pinout & Package
TSSOP-16 package (5.00 mm × 4.40 mm, 1.2 mm max height), JEDEC MO-153 compliant, lead finish NiPdAu/Sn, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A) | Select input A | LSB of 3-bit binary select code; determines data source index with B and C |
| 2 (B) | Select input B | Middle bit of select code; enables full 1-of-8 decoding when combined with A and C |
| 3 (C) | Select input C | MSB of select code; completes 3-bit address for D0–D7 input selection |
| 4 (D0) | Data input 0 | Lowest-indexed data source; routed to Y/W when A=B=C=0 |
| 5 (D1) | Data input 1 | Routed to Y/W when A=1, B=C=0; supports sequential data stream selection |
| 6 (D2) | Data input 2 | Enables 3-bit addressable routing for sensor mux or register bank access |
| 7 (D3) | Data input 3 | Part of standard 8-input set; used in address/data bus gating applications |
| 8 (GND) | Ground reference | Primary return path for all internal logic and output currents |
| 9 (D4) | Data input 4 | Upper-half data source; selected when C=1, A=B=0 (binary 100) |
| 10 (D5) | Data input 5 | Supports full 8-channel selection for ADC channel routing or display segment control |
| 11 (D6) | Data input 6 | Used in multi-function I/O expansion where discrete signals require time-multiplexing |
| 12 (D7) | Data input 7 | Highest-indexed input; selected when A=B=C=1 (binary 111) |
| 13 (OE) | Output enable (active low) | Strobe controls both Y and W outputs; high = high-impedance state for bus sharing |
| 14 (W) | Inverted output | Complementary to Y; eliminates need for external inverters in differential bus drivers |
| 15 (Y) | True output | Main data output; driven low/high per selected Dn input when OE = low |
| 16 (VCC) | Positive supply | Single power rail for entire device; bypass capacitor (0.1 µF) required near pin |
Key Features
| Feature | Design Value |
|---|---|
| 3-state complementary outputs | Enables bidirectional bus arbitration using single OE control-no external tri-state logic needed |
| Wide 2 V–6 V supply range | Eliminates level shifters when interfacing with 3.3 V microcontrollers and 5 V peripherals |
| High-current outputs (±6 mA @ 5 V) | Drives LSTTL loads directly-reduces component count in legacy system upgrades |
| Low ICC (80 μA max) | Reduces system-level quiescent power in always-on monitoring circuits and sleep-mode logic |
| Perform parallel-to-serial conversion | Converts 8-bit parallel data into time-multiplexed serial stream using external clock on select lines |
Applications
| Microcontroller I/O Expansion | Address/Data Bus Multiplexing |
|---|---|
Use Scenario: Expanding limited GPIO count on an MCU to manage 8 discrete sensors or actuators via time-shared read/write cycles. IC Role / Device Role / Timing Role: SN74HC251PW acts as a programmable input selector, routing one of eight analog/digital signals to a shared ADC input or UART RX line under MCU-controlled A/B/C select lines. Use Value: Reduces PCB real estate and BOM cost versus adding multiple dedicated I/O expanders; leverages existing MCU clock and GPIO for full 8-channel control. | Use Scenario: Sharing a single 8-bit data bus between multiple peripheral ICs (e.g., EEPROM, DAC, GPIO expander) in a resource-constrained embedded controller. IC Role / Device Role / Timing Role: SN74HC251PW functions as a bus gate, enabling only one peripheral's data output onto the common bus while others remain in high-Z state via OE control. Use Value: Eliminates need for dedicated bus transceivers or complex arbitration logic-simplifies layout and reduces signal integrity risk from bus contention. |
| Sensor Signal Routing | Digital Test Equipment Channel Selection |
Use Scenario: Selecting among eight temperature, pressure, or voltage sensor outputs for periodic sampling in an industrial data logger. IC Role / Device Role / Timing Role: SN74HC251PW serves as a hardware-based analog front-end switch, presenting selected sensor signal to a precision ADC while maintaining signal integrity via low-capacitance CMOS inputs. Use Value: Avoids software-based polling delays and ensures deterministic sampling intervals; complementary outputs support differential acquisition if required. | Use Scenario: Configuring automated test equipment to apply stimulus or capture response from one of eight DUT (device-under-test) pins during functional verification. IC Role / Device Role / Timing Role: SN74HC251PW operates as a programmable signal path selector, routing test signals through a single instrument channel to reduce channel count requirements. Use Value: Low propagation delay (19 ns typ) ensures precise timing alignment in high-speed digital test patterns; 3-state outputs prevent back-driving during reconfiguration. |
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 |
|---|---|---|---|
| SN74HC151PWR | Same logic function and pinout, but lacks complementary outputs (W); Y only | Requires external inverter for inverted signal paths; less suitable for differential bus driving | Choose when only true output is needed and board space allows added inverter |
| 74LVX151M | Lower VCC range (2.7 V–3.6 V), higher speed (tpd = 6.5 ns typ @ 3.3 V), different pinout | Not pin-compatible; requires PCB redesign; optimized for 3.3 V-only systems | Prefer for new 3.3 V designs demanding sub-7 ns latency and lower supply voltage |
Compared with SN74HC151PWR and 74LVX151M, the SN74HC251PW uniquely provides true/inverted outputs in a drop-in TSSOP-16 package, enabling simplified bus interface design without additional logic-making it optimal for industrial control and mixed-voltage upgrade projects.
Availability
SN74HC251PW is available at Aetrix Electronics and suitable for industrial control systems, embedded data loggers, and test equipment requiring stable component supply and long-term manufacturability.
Supply support for SN74HC251PW 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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.
The SN74HC251PW belongs to TI's HC logic family-designed for high-noise-immunity, low-power CMOS operation in general-purpose digital systems requiring TTL-compatible interfacing and reliable 3-state bus control.
FAQ
What is the maximum operating frequency supported by the SN74HC251PW?
The SN74HC251PW does not specify a maximum clock frequency in its datasheet because it is a combinational logic device-not clocked. Its usable switching rate depends on propagation delay (tpd ≤ 51 ns at VCC = 6 V, CL = 150 pF) and system setup/hold timing margins. For reliable operation with fast select transitions, ensure input transition times meet Δt/Δv ≤ 400 ns (VCC = 6 V) to avoid metastability or glitches. The SN74HC251PW remains fully functional across its entire recommended operating range without internal clock constraints.
Does the SN74HC251PW require external pull-up or pull-down resistors on its inputs?
No, the SN74HC251PW does not require external pull-up or pull-down resistors on its inputs when actively driven, as its CMOS inputs have negligible leakage (≤1 μA). However, TI explicitly mandates that all unused inputs-including A, B, C, D0–D7, and OE-must be tied to VCC or GND to prevent floating states that cause increased ICC, oscillation, or undefined outputs. Leaving any input unconnected violates the recommended operating conditions and risks erratic behavior in the SN74HC251PW.
Can the SN74HC251PW drive a 50-pF capacitive load reliably at 6 V supply?
Yes, the SN74HC251PW is fully characterized for CL = 50 pF and CL = 150 pF loads. At VCC = 6 V and TA = 25 °C, its typical propagation delay is 19 ns and maximum is 51 ns into 50-pF, meeting timing specs across the full operating temperature range (−40 °C to +85 °C). Output voltage levels (VOH ≥ 5.48 V, VOL ≤ 0.26 V at IOL = 7.8 mA) and drive strength remain within specification, confirming robust 50-pF load handling for the SN74HC251PW in high-speed digital interfaces.
Is the SN74HC251PW pin-compatible with the SN74HC151 series?
Yes-the SN74HC251PW is functionally and pin-compatible with the SN74HC151 in TSSOP-16 (PW) packaging. Both share identical pin assignments for A, B, C, D0–D7, OE, Y, VCC, and GND. The key distinction is that the SN74HC251PW provides complementary outputs (Y and W), whereas the SN74HC151 offers only Y. This makes the SN74HC251PW a superset replacement: it can substitute for SN74HC151 in existing designs, with W left unconnected if unused.
What is the thermal resistance (RθJA) of the SN74HC251PW in its TSSOP-16 package?
The junction-to-ambient thermal resistance (RθJA) for the SN74HC251PW in TSSOP-16 (PW) package is 108 °C/W, as specified in Section 5.3 of the TI datasheet. This value assumes standard JEDEC high-K test board conditions (2S2P). In practical layouts with 2–4 cm² copper pour and 2–4 thermal vias under the exposed pad (if present), actual RθJA may improve to ~60–80 °C/W. The SN74HC251PW's low ICC (80 μA max) results in minimal self-heating, making thermal derating unnecessary in most industrial applications.
SN74HC251PW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- 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-TSSOP
SN74HC251PW FAQ
1.How can I place an order for SN74HC251PW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC251PW 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 SN74HC251PW reliable?
The price and inventory of SN74HC251PW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC251PW is usually 5 days.
3.What payment methods are accepted for SN74HC251PW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC251PW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC251PW?
SN74HC251PW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC251PW 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 SN74HC251PW?
For technical support, including SN74HC251PW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC251PW requirements.
6.How does Aetrix verify that SN74HC251PW is sourced from the original manufacturer or authorized distributors?
All SN74HC251PW 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 SN74HC251PW meets industry standards.
7.What is the process for return or replacement of SN74HC251PW?
All SN74HC251PW units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC251PW, 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 SN74HC251PW part is unused and in its original packaging.
Return procedure for SN74HC251PW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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