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Texas Instruments CD74AC251M
- Part No.:
- CD74AC251M
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
CD74AC251M.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:636
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Product details
Overview
CD74AC251M from Texas Instruments is an 8-input CMOS multiplexer with true (Y) and complement (Y̅) outputs, Output Enable (OE) control, and three-state capability. It operates from 1.5V to 5.5V, delivers ±24mA output drive, exhibits 6ns typical propagation delay at 5V/25°C/50pF, and supports industrial temperature range (–55°C to +125°C). It is used in data routing, signal selection, and bus multiplexing within digital logic subsystems.
For engineers reviewing the CD74AC251M datasheet, CD74AC251M pinout, CD74AC251M application, or CD74AC251M equivalent, key selection criteria include its dual-output architecture, rail-to-rail supply flexibility, high-speed switching performance, ESD robustness (>2kV), and SOIC-16 package compatibility with legacy TTL/CMOS systems.
Technical Context
The CD74AC251M implements a single-pole, eight-throw analog/digital multiplexer function using advanced CMOS logic. Its address decoding logic accepts three select inputs (S2–S0) to route one of eight data inputs (I0–I7) to both Y and Y̅ outputs simultaneously when OE is low.
Three-state operation is controlled exclusively by the active-low OE input: when high, both outputs enter high-impedance mode independent of select or data states. Propagation delays are balanced between true and complement paths, and input-to-output timing varies predictably with VCC (e.g., 12.3ns max at 5V, –55°C to +125°C).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 1.5V to 5.5V - enables interoperability across 1.8V, 3.3V, and 5V logic domains without level shifters. |
| Propagation Delay (tPLH/tPHL) | 12.3ns max at 5V, –55°C to +125°C - ensures deterministic timing in high-speed synchronous logic designs. |
| Output Drive Current | ±24mA - directly drives 15 FAST™ ICs or 50Ω transmission lines, reducing need for external buffers. |
| Input/Output Voltage Levels | VIH = 3.85V min, VIL = 1.65V max at VCC = 5.5V - provides 30% noise margin, enhancing noise immunity in noisy environments. |
| ESD Protection | >2kV per MIL-STD-883 Method 3015 - improves handling robustness and field reliability in manufacturing and deployment. |
| Operating Temperature | –55°C to +125°C - qualified for aerospace, automotive under-hood, and industrial control applications. |
| Quiescent Supply Current | 160μA max - enables low-static-power operation in battery-backed or energy-constrained systems. |
Pinout & Package
CD74AC251M is housed in a 16-pin SOIC (D) package measuring 9.9mm × 6mm (including pins), with body size 9.9mm × 3.9mm. The package is RoHS-compliant, NIPDAU lead-finished, and rated MSL Level-1 (unlimited floor life).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1–4, 12–15 (I0–I3, I4–I7) | Data Inputs | Eight bidirectional CMOS-compatible inputs; selected via S2/S1/S0 to drive Y/Y̅ outputs. |
| 5 (Y) | True Output | Active-high routed data output; enters high-Z when OE = HIGH. |
| 6 (Y̅) | Complement Output | Inverted copy of Y; synchronized and balanced delay relative to Y path. |
| 7 (OE) | Output Enable | Active-low control: LOW enables Y/Y̅; HIGH forces both into three-state (high-Z) mode. |
| 8 (GND) | Ground Reference | Primary return path for all internal logic and I/O; must be low-impedance connection. |
| 9–11 (S2, S1, S0) | Select Inputs | 3-bit binary address determining which Ix input appears on Y/Y̅; latched internally on transition. |
| 16 (VCC) | Power Supply | Single positive supply (1.5–5.5V); requires local 0.1μF bypass capacitor per TI layout guidelines. |
Key Features
| Feature | Design Value |
|---|---|
| Buffered Inputs | Reduces capacitive loading on upstream drivers and improves signal integrity across PCB traces. |
| Balanced Propagation Delays | Minimizes skew between Y and Y̅ outputs, critical for differential signaling and clock/data alignment. |
| SCR-Latchup Resistant Process | Prevents destructive latch-up under transient overvoltage or ESD events, meeting industrial reliability standards. |
| 1.5V–5.5V Wide-Voltage Operation | Eliminates need for separate voltage translators in mixed-supply systems (e.g., 1.8V FPGA interfacing to 5V peripherals). |
| ±24mA Output Drive | Supports fanout to 15 FAST™ devices or direct termination of 50Ω lines-reducing component count and board space. |
Applications
| Industrial PLC I/O Multiplexing | Digital Test Equipment Signal Routing |
|---|---|
|
Use Scenario: A programmable logic controller routes sensor inputs (temperature, pressure, flow) to a single ADC channel using time-division sampling. IC Role / Device Role / Timing Role: CD74AC251M acts as a high-reliability analog/digital multiplexer, selecting one of eight sensor signals under microcontroller control via S2–S0 and OE. Use Value: Its –55°C to +125°C rating and >2kV ESD protection ensure stable operation in electrically noisy factory environments without signal corruption or failure. |
Use Scenario: Automated test equipment switches between multiple DUT (device-under-test) signal lines to a common measurement interface. IC Role / Device Role / Timing Role: CD74AC251M serves as a fast, low-skew signal selector, enabling precise timing-controlled access to up to eight test points using synchronous address updates. Use Value: 12.3ns max propagation delay at full temperature range guarantees sub-15ns timing resolution, supporting high-throughput parametric testing. |
| Legacy System Bus Expansion | Embedded Microcontroller Peripheral Sharing |
|
Use Scenario: A retro-computing restoration project adds new peripheral cards to a vintage 8-bit bus while preserving original address decoding. IC Role / Device Role / Timing Role: CD74AC251M functions as a bus-aware multiplexer, steering memory-mapped I/O reads/writes between legacy and new hardware based on address bits. Use Value: Pin-compatible replacement for older TTL multiplexers (e.g., 74LS251), with identical SOIC-16 footprint and 5V-tolerant inputs simplifying drop-in upgrades. |
Use Scenario: An ARM Cortex-M4 microcontroller shares limited GPIO resources among UART, SPI, and debug interfaces via dynamic reconfiguration. IC Role / Device Role / Timing Role: CD74AC251M provides hardware-level peripheral signal routing, allowing software to switch functional assignments without firmware-modified pinmux. Use Value: Dual Y/Y̅ outputs enable simultaneous monitoring of selected signal and its inverse-useful for logic analyzers or fault-detection circuits. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-input multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AC251N | Same AC logic family, identical pinout and specs, but in PDIP-16 package (not surface-mount). | Suitable for prototyping or through-hole assembly; lacks SOIC thermal performance and board density. | Choose SN74AC251N only if manual soldering or breadboard evaluation is required; CD74AC251M remains optimal for production SMT. |
| CD74HC251E | HC-family variant: slower (24ns typ @ 6V), narrower VCC range (2V–6V), lower drive (±4mA), no 1.5V operation. | Limited to 3.3V/5V systems; insufficient drive for transmission-line termination or FAST™ fanout. | Select CD74HC251E only for cost-sensitive, low-speed applications where 1.5V support and ±24mA drive are unnecessary. |
Compared with SN74AC251N and CD74HC251E, the CD74AC251M uniquely combines SOIC-16 manufacturability, 1.5V–5.5V universal supply compatibility, and ±24mA drive-making it the only choice for compact, wide-voltage, high-drive multiplexing in volume production.
Availability
CD74AC251M is available at Aetrix Electronics and suitable for industrial automation, test instrumentation, legacy system upgrades, and embedded peripheral management requiring stable component supply across extended temperature and voltage ranges.
Supply support for CD74AC251M 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 decades of expertise in high-reliability logic families and industrial-grade components.
The CD74AC251M belongs to TI's Advanced CMOS (AC) logic series, designed specifically for applications demanding wide supply voltage range, high noise immunity, and robust ESD performance in harsh environments.
FAQ
What is the maximum operating supply voltage for CD74AC251M?
The CD74AC251M supports a maximum supply voltage of 5.5V, as specified in its Absolute Maximum Ratings table. Exceeding this value-even momentarily-may cause permanent damage. The device is fully characterized from 1.5V to 5.5V, with guaranteed performance across that entire range, including propagation delay, drive strength, and logic thresholds.
Does CD74AC251M support 1.8V logic systems?
Yes, CD74AC251M fully supports 1.8V operation: its minimum recommended VCC is 1.5V, and all electrical characteristics-including VIH/VIL thresholds, propagation delay, and output drive-are specified down to that level. At 1.8V, it maintains balanced noise margins and operates reliably across the full –55°C to +125°C temperature range.
Can CD74AC251M drive a 50Ω transmission line directly?
Yes, CD74AC251M is explicitly rated to drive 50Ω transmission lines, verified per TI's datasheet Section 4.4 footnote (2). With ±24mA output current at 4.5V, it meets the minimum 50Ω drive requirement at 85°C and 75Ω at 125°C, eliminating the need for external line drivers in high-speed digital interconnects.
What happens to the outputs when OE is HIGH on CD74AC251M?
When OE is HIGH, both Y and Y̅ outputs enter a high-impedance (three-state) condition regardless of the states of S2–S0 or I0–I7 inputs. This allows multiple CD74AC251M devices to share a common bus without contention. Leakage current in this state is ≤±10μA over temperature, ensuring minimal loading on downstream circuitry.
Is CD74AC251M pin-compatible with older 74LS251 multiplexers?
No, CD74AC251M is not pin-compatible with 74LS251: although both are 16-pin SOIC multiplexers with identical pin numbering, the LS251 uses different internal logic (TTL-based, no Y̅ output, no OE pin), and its pin 6 is unused-not Y̅. CD74AC251M's pin 6 is a functional inverted output, making direct substitution impossible without PCB redesign.
CD74AC251M Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Multiplexer
- Circuit:
- 1 x 8:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 75mA, 75mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 1.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
CD74AC251M FAQ
1.How can I place an order for CD74AC251M through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74AC251M 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 CD74AC251M reliable?
The price and inventory of CD74AC251M are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74AC251M is usually 5 days.
3.What payment methods are accepted for CD74AC251M?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74AC251M transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74AC251M?
CD74AC251M orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74AC251M 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 CD74AC251M?
For technical support, including CD74AC251M datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74AC251M requirements.
6.How does Aetrix verify that CD74AC251M is sourced from the original manufacturer or authorized distributors?
All CD74AC251M 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 CD74AC251M meets industry standards.
7.What is the process for return or replacement of CD74AC251M?
All CD74AC251M units undergo pre-shipment inspection (PSI). If there is an issue with CD74AC251M, 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 CD74AC251M part is unused and in its original packaging.
Return procedure for CD74AC251M:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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