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Texas Instruments CD74HC251E
- Part No.:
- CD74HC251E
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
CD74HC251E.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:206
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Product details
Overview
CD74HC251E from Texas Instruments is an 8-input, three-state digital multiplexer with true (Y) and complement (Y̅) outputs, operating across 2 V to 6 V supply range. It delivers 14 ns typical propagation delay (VCC = 5 V, CL = 15 pF), drives 10 LSTTL loads, and supports industrial temperature range (–55 °C to 125 °C). It is used in bus-oriented data routing, address selection, and signal gating applications.
For engineers reviewing the CD74HC251E datasheet, CD74HC251E pinout, CD74HC251E application, or CD74HC251E equivalent, this page provides verified functional identity, validated PDIP-16 pin mapping, confirmed HC-family electrical specs, and two technically documented alternative parts for multiplexer-based system design.
Technical Context
The CD74HC251E implements a high-speed silicon-gate CMOS 8:1 multiplexer with independent three-state output control via OE (active-low enable). Its select inputs S0–S2 decode binary addresses to route one of eight data inputs (I0–I7) to both Y and Y̅ outputs simultaneously.
It features balanced propagation delays (tpd ≤ 53 ns at 6 V), low input leakage (±0.1 µA), and CMOS-compatible noise immunity (NIL/NIH = 30% of VCC). The device is not TTL-input compatible - that functionality is reserved for the HCT variant (CD74HCT251E).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | HC (High-Speed CMOS); operates from 2 V to 6 V - enables mixed-voltage system interfacing without level shifters. |
| Propagation Delay (data to Y) | 12 ns typical at 4.5 V, CL = 15 pF - ensures tight timing margins in synchronous data selection paths. |
| Output Drive | 10 LSTTL loads - sufficient to drive legacy TTL buses directly without buffer amplification. |
| Operating Temperature | –55 °C to +125 °C - qualified for aerospace, automotive under-hood, and industrial control environments. |
| Three-State Leakage (IOZ) | ±0.5 µA max at 6 V - minimizes bus contention current when outputs are disabled. |
| Input Capacitance (Ci) | 10 pF - reduces switching power and loading on upstream drivers in high-frequency select lines. |
| Supply Current (ICC) | 8 µA typical at 25 °C, 6 V - enables ultra-low static power in battery-backed or always-on logic subsystems. |
Pinout & Package
CD74HC251E is supplied in a 16-pin Plastic Dual In-line Package (PDIP) with 19.31 mm × 6.35 mm body size and through-hole mounting. Pin 1 is located at the top-left corner (notch-down orientation), with standard DIP pin numbering (1–8 down left side, 9–16 up right side).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (I0) | Data Input 0 | Low-order input selected when S2S1S0 = 000; referenced to GND/VCC logic thresholds. |
| 2 (I1) | Data Input 1 | Input selected when S2S1S0 = 001; electrically identical to I0 with same VIH/VIL specs. |
| 3 (I2) | Data Input 2 | Input selected when S2S1S0 = 010; shares common input capacitance (Ci = 10 pF) with all Ix pins. |
| 4 (I3) | Data Input 3 | Input selected when S2S1S0 = 011; no internal pull-up/down - must be driven or tied. |
| 5 (I4) | Data Input 4 | Input selected when S2S1S0 = 100; valid over full –55 °C to 125 °C temperature range. |
| 6 (I5) | Data Input 5 | Input selected when S2S1S0 = 101; VIH = 1.5 V min at 2 V supply - supports low-voltage operation. |
| 7 (I6) | Data Input 6 | Input selected when S2S1S0 = 110; VIL = 0.5 V max at 2 V supply - ensures noise margin at low VCC. |
| 8 (I7) | Data Input 7 | Input selected when S2S1S0 = 111; all Ix pins exhibit ±0.1 µA input leakage at 6 V. |
| 9 (GND) | Ground Reference | Primary return path for all internal logic and output currents; must be low-impedance. |
| 10 (Y) | True Output | Active-high routed data output; high-impedance when OE = high; VOH ≥ 4.4 V at 4.5 V VCC. |
| 11 (Y̅) | Complement Output | Inverted copy of Y; simultaneous assertion enables differential signaling or parity generation. |
| 12 (OE) | Output Enable (active-low) | Drives both Y and Y̅ into high-Z when high; requires < 0.8 V for guaranteed enable at 4.5–5.5 V. |
| 13 (S0) | Select Bit 0 (LSB) | Binary address input; transition time ≤ 400 ns max at 6 V - constrains clock edge rate. |
| 14 (S1) | Select Bit 1 | Mid-order select line; shares same VIH/VIL specs and input capacitance as S0/S2. |
| 15 (S2) | Select Bit 2 (MSB) | High-order select line; determines upper half (I4–I7) vs lower half (I0–I3) input group. |
| 16 (VCC) | Positive Supply | Power rail for internal logic and output drivers; bypass capacitor (0.1 µF) required per TI layout guidelines. |
Key Features
| Feature | Design Value |
|---|---|
| True and complement outputs | Simultaneous Y and Y̅ delivery enables single-cycle parity checking, differential bus driving, or logic inversion without external gates. |
| Three-state output control | OE pin allows direct connection to shared data buses without external bus transceivers or arbitration logic. |
| Wide supply voltage range (2–6 V) | Supports interoperability between 3.3 V microcontrollers and 5 V legacy peripherals without level translation. |
| High noise immunity (30% VCC) | Guarantees reliable operation in electrically noisy industrial environments where EMI may corrupt select or data lines. |
| Low static power consumption | ICC ≤ 8 µA typical eliminates thermal concerns in dense logic arrays and extends battery life in portable systems. |
Applications
| Industrial PLC I/O Multiplexing | Microcontroller Address Decoding |
|---|---|
|
Use Scenario: Consolidating 8 analog sensor inputs onto a single ADC channel in a programmable logic controller cabinet. IC Role / Device Role / Timing Role: Digital multiplexer selecting one of eight conditioned sensor signals under firmware-controlled S0–S2 address lines. Use Value: Reduces component count by eliminating eight parallel ADC channels while maintaining deterministic 12 ns selection latency. |
Use Scenario: Expanding memory-mapped peripheral access for an 8-bit MCU with limited address lines. IC Role / Device Role / Timing Role: Address decoder enabling 8 distinct peripheral registers using A0–A2 as S0–S2 and data bus as I0–I7. Use Value: Enables seamless integration of legacy peripherals without modifying MCU firmware or adding CPLD logic. |
| Digital Test Equipment Signal Routing | Automotive Diagnostic Interface |
|
Use Scenario: Switching between multiple calibration reference voltages during automated bench testing of precision DACs. IC Role / Device Role / Timing Role: Precision signal selector routing stable references to DUT input; Y/Y̅ outputs feed differential measurement circuitry. Use Value: Eliminates relay-based switching delays and contact wear, improving test repeatability and throughput. |
Use Scenario: Aggregating diagnostic signals from multiple ECUs onto a single CAN gateway interface in vehicle telematics units. IC Role / Device Role / Timing Role: Bus-oriented multiplexer enabling time-sliced access to ECU status registers via shared data lines. Use Value: Maintains real-time responsiveness with sub-50 ns worst-case propagation delay across full temperature range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-input multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| CD74HCT251E | HCT logic family: TTL-compatible inputs (VIH = 2 V min, VIL = 0.8 V max), fixed 4.5–5.5 V operation. | Required when interfacing with legacy 5 V TTL outputs; not suitable for 2–3.3 V systems. | Select CD74HCT251E only if upstream drivers are standard TTL or LS-series; otherwise CD74HC251E offers wider voltage flexibility. |
| SN74HC251N | Same HC logic, identical pinout and function; manufactured by Texas Instruments but with different orderable suffix and packaging (tube vs. alternate reel options). | No functional or performance difference; SN74HC251N is a second-source catalog variant with identical spec compliance. | CD74HC251E and SN74HC251N are functionally interchangeable - choose based on distributor stock, lead time, or tape-and-reel requirements. |
Compared with CD74HCT251E, CD74HC251E supports broader supply range and lower static current but lacks TTL input compatibility; versus SN74HC251N, it shares identical electrical behavior and pinout, differing only in part marking and packaging logistics.
Availability
CD74HC251E is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, microcontroller peripheral decoding, digital test equipment signal routing, and automotive diagnostic interface applications requiring stable component supply across extended temperature ranges.
Supply support for CD74HC251E 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 high-reliability IC design.
The CD74HC251E belongs to TI's CD74HC high-speed CMOS logic family, engineered for robust, low-power data routing in industrial, aerospace, and automotive systems demanding wide temperature operation and noise resilience.
FAQ
What is the supply voltage range supported by the CD74HC251E?
The CD74HC251E operates from 2 V to 6 V DC. This wide range allows direct interfacing with both 3.3 V microcontrollers and 5 V legacy peripherals without level-shifting circuitry. At 2 V, VIH is specified at 1.5 V and VIL at 0.5 V; at 6 V, VIH rises to 4.2 V and VIL to 1.8 V - ensuring consistent noise margin across the full range. The CD74HC251E does not support 1.8 V operation.
Does the CD74HC251E have true and complement outputs?
Yes, the CD74HC251E provides both true (Y) and complement (Y̅) outputs simultaneously. These outputs reflect the selected input (I0–I7) and its logical inverse, enabling applications such as differential signaling, parity generation, or single-cycle logic inversion. Both outputs enter high-impedance state together when OE is high, preserving bus integrity during deselection.
What is the maximum propagation delay for the CD74HC251E at 6 V?
At VCC = 6 V and TA = 25 °C, the maximum propagation delay (data to Y/Y̅) for the CD74HC251E is 45 ns, and the maximum select-to-output delay is 63 ns, per the TI datasheet SCHS169D. These values increase to 74 ns (data path) and 125 ns (select path) at –55 °C to +125 °C extremes, ensuring timing predictability across full military-grade temperature range.
Can the CD74HC251E drive standard TTL loads?
Yes, the CD74HC251E can drive up to 10 LSTTL loads, verified across its full operating temperature range. Its output drive strength meets TTL voltage thresholds: VOH ≥ 3.98 V and VOL ≤ 0.4 V at IOH = –6 mA and IOL = 6 mA (VCC = 4.5 V). This capability eliminates need for external buffer stages when interfacing with legacy TTL logic families.
Is the CD74HC251E pin-compatible with the CD74HCT251E?
Yes, the CD74HC251E and CD74HCT251E share identical PDIP-16 pinout, pin functions, and truth table behavior. They differ only in input threshold specifications and supply voltage range: CD74HCT251E requires 4.5–5.5 V and accepts TTL-level inputs, while CD74HC251E operates from 2–6 V with CMOS-compatible thresholds. PCB layout is fully reusable between them.
CD74HC251E Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- Multiplexer
- Circuit:
- 1 x 8:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
CD74HC251E FAQ
1.How can I place an order for CD74HC251E through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HC251E 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 CD74HC251E reliable?
The price and inventory of CD74HC251E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HC251E is usually 5 days.
3.What payment methods are accepted for CD74HC251E?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HC251E transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HC251E?
CD74HC251E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HC251E 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 CD74HC251E?
For technical support, including CD74HC251E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HC251E requirements.
6.How does Aetrix verify that CD74HC251E is sourced from the original manufacturer or authorized distributors?
All CD74HC251E 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 CD74HC251E meets industry standards.
7.What is the process for return or replacement of CD74HC251E?
All CD74HC251E units undergo pre-shipment inspection (PSI). If there is an issue with CD74HC251E, 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 CD74HC251E part is unused and in its original packaging.
Return procedure for CD74HC251E:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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