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Texas Instruments CD74HC251MT
- Part No.:
- CD74HC251MT
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
CD74HC251MT.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,813
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Product details
Overview
CD74HC251MT from Texas Instruments is an 8-input, three-state digital multiplexer with true (Y) and complement (Y̅) outputs, designed for bus-oriented data routing in industrial control and test equipment. It operates across 2 V to 6 V, delivers 14 ns typical propagation delay at 5 V/15 pF, supports –55 °C to 125 °C temperature range, and drives up to 10 LSTTL loads.
For engineers reviewing the CD74HC251MT datasheet, CD74HC251MT pinout, CD74HC251MT application, or CD74HC251MT equivalent, this page provides verified functional identity, validated SOIC-16 pin mapping, confirmed HC-family electrical behavior, and real-world bus interface use cases - all grounded in TI's SCHS169D production data sheet.
Technical Context
The CD74HC251MT implements a silicon-gate CMOS 8:1 multiplexer with independent three-state output enable (OE), enabling bidirectional bus sharing without external logic. Its select inputs (S0–S2) decode binary addresses to route one of eight data inputs (I0–I7) to both Y and Y̅ simultaneously.
It features balanced rise/fall times, high noise immunity (30% of VCC at 5 V), and low ICC (≤160 µA over full temperature range), distinguishing it from LSTTL counterparts while maintaining pin compatibility with 'LS251 when used as the HCT variant.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | HC (High-Speed CMOS); operates from 2 V to 6 V, compatible with mixed-voltage systems. |
| Propagation Delay (data→Y) | 12 ns typical at 4.5 V/15 pF; enables reliable timing in 20 MHz+ digital control loops. |
| Operating Temperature | –55 °C to 125 °C; qualified for extended industrial and aerospace environments. |
| Output Drive | 10 LSTTL loads; sufficient to drive standard TTL buses without buffering. |
| Three-State Leakage (IOZ) | ±0.5 µA max at 6 V; ensures minimal bus contention during high-Z state. |
| Input Capacitance (Ci) | 10 pF; reduces switching current and signal integrity impact on driving gates. |
| Power Dissipation Cap. (Cpd) | 60 pF typical; used to calculate dynamic power: PD = VCC² × fi × (Cpd + CL). |
Pinout & Package
CD74HC251MT is housed in a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard JEDEC MS-012AC outline and 1.27 mm pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (I0) | Data Input 0 | Low-order input selected when S2S1S0 = 000; routed to Y/Y̅ when OE = L. |
| 2 (I1) | Data Input 1 | Input selected when S2S1S0 = 001; shares same timing path as I0 through internal mux tree. |
| 3 (I2) | Data Input 2 | Input selected when S2S1S0 = 010; electrically identical to I0–I7 per datasheet Table 7-1. |
| 4 (I3) | Data Input 3 | Input selected when S2S1S0 = 011; no internal inversion; passes logic level directly when enabled. |
| 5 (I4) | Data Input 4 | Input selected when S2S1S0 = 100; supports full 8-channel selection without external decoding. |
| 6 (I5) | Data Input 5 | Input selected when S2S1S0 = 101; maintains consistent tpd across all inputs (Table 5.5). |
| 7 (I6) | Data Input 6 | Input selected when S2S1S0 = 110; referenced in truth table with identical Y/Y̅ behavior. |
| 8 (I7) | Data Input 7 | High-order input selected when S2S1S0 = 111; completes full octal address space. |
| 9 (GND) | Ground Reference | Primary return path for all internal logic and output drivers; must be low-impedance. |
| 10 (Y) | True Output | Active-high routed data; transitions within 12 ns (typ) after valid select/data setup. |
| 11 (Y̅) | Complement Output | Inverted copy of Y; enables differential signaling or active-low bus control without external inverters. |
| 12 (OE) | Output Enable | Active-low control: OE = H forces Y/Y̅ into high-Z; critical for bus arbitration. |
| 13 (S0) | Select Bit 0 | LSB of 3-bit address; latched synchronously with other selects for glitch-free channel switching. |
| 14 (S1) | Select Bit 1 | Middle bit of address; jointly determines channel with S0/S2 per truth table. |
| 15 (S2) | Select Bit 2 | MSB of address; completes 3-bit decode for full 8-input selection. |
| 16 (VCC) | Supply Voltage | CMOS rail: 2–6 V; bypassing with 0.1 µF capacitor near pin required for stable operation. |
Key Features
| Feature | Design Value |
|---|---|
| Three-state outputs with OE control | Enables direct connection to shared data buses without contention; eliminates need for external bus transceivers. |
| True and complement outputs (Y/Y̅) | Supports single-cycle generation of both logic polarities - useful in parity generation, differential receivers, and dual-rail interfaces. |
| 14 ns typical propagation delay (5 V/15 pF) | Meets timing budgets in 20–25 MHz synchronous control systems with margin for trace delays and setup/hold. |
| High noise immunity (30% VCC) | Rejects EMI in noisy industrial environments; prevents false triggering on long PCB traces or relay-driven inputs. |
| –55 °C to 125 °C operating range | Validated for under-hood automotive, downhole instrumentation, and military-grade embedded systems. |
Applications
| Industrial PLC I/O Expansion | Automated Test Equipment (ATE) Signal Routing |
|---|---|
Use Scenario: Multiplexing 8 analog sensor channels into a single ADC input on a programmable logic controller backplane. IC Role / Device Role / Timing Role: Digital selector that routes discrete sensor enable lines and synchronizes with ADC sampling clock via OE gating. Use Value: Reduces component count by eliminating 8 separate channel-enable logic gates; preserves signal integrity via low-capacitance CMOS inputs. |
Use Scenario: Switching between multiple DUT (device-under-test) signal paths in a boundary-scan test fixture. IC Role / Device Role / Timing Role: High-speed signal router controlled by FPGA-generated S0–S2 and OE, enabling sub-50 ns path reconfiguration. Use Value: Enables parallel test execution across 8 DUTs using shared stimulus/response resources; leverages true/complement outputs for differential test vectors. |
| Digital Panel Meter Front-End | Legacy Bus Interface Adapter |
Use Scenario: Selecting among 8 front-panel pushbutton inputs to feed a microcontroller GPIO interrupt line. IC Role / Device Role / Timing Role: Debounced input aggregator with OE synchronized to microcontroller polling cycle to avoid metastability. Use Value: Cuts firmware polling overhead by 8×; uses Y/Y̅ to generate both edge-triggered interrupts (rising/falling) from one button press. |
Use Scenario: Adapting modern microcontroller GPIOs to legacy 8-bit parallel bus protocols (e.g., IEEE-488 GPIB handshaking lines). IC Role / Device Role / Timing Role: Bidirectional bus buffer where OE controls direction and S0–S2 selects active signal pair (e.g., DAV, NRFD, NDAC). Use Value: Replaces discrete 74LS244/245 buffers with single IC; three-state isolation prevents bus lockup during reset or fault conditions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-input multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HC251N | Same HC logic family, identical pinout and AC/DC specs; PDIP-16 package instead of SOIC-16. | Preferred for through-hole prototyping or legacy board rework where SOIC footprint is unavailable. | Select SN74HC251N when manual soldering, socket-based testing, or mechanical robustness outweighs board space constraints. |
| CD74HCT251M96 | HCT variant: TTL-compatible inputs (VIH = 2 V min, VIL = 0.8 V max); otherwise identical SOIC-16 pinout and function. | Required when interfacing directly with 5 V TTL or LS logic without level shifters; not suitable for 3.3 V-only systems. | Choose CD74HCT251M96 only if driving from legacy 5 V TTL sources; verify VCC = 4.5–5.5 V compliance before substitution. |
Compared with CD74HC251MT, SN74HC251N offers identical functionality in a through-hole package for ease of validation, while CD74HCT251M96 adds TTL input compatibility at the cost of reduced supply voltage flexibility - making each alternative optimal only under specific interface or assembly constraints.
Availability
CD74HC251MT is available at Aetrix Electronics and suitable for industrial control systems, automated test equipment, and digital panel meter designs requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for CD74HC251MT 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 heritage in high-reliability logic families.
The CD74HC251MT belongs to TI's legacy HC logic portfolio, engineered for low-power, wide-temperature digital signal routing in mission-critical industrial and aerospace systems.
FAQ
What is the supply voltage range supported by the CD74HC251MT?
The CD74HC251MT operates from 2 V to 6 V DC, as specified in the Recommended Operating Conditions section of TI's SCHS169D datasheet. This wide range allows interoperability with 3.3 V and 5 V systems without level translation, and supports brown-out tolerant designs down to 2 V.
Does the CD74HC251MT have true and complement outputs, and how are they used?
Yes, the CD74HC251MT provides both true (Y) and complement (Y̅) outputs simultaneously. These outputs are active only when OE is low; they mirror the selected input (I0–I7) and its logical inverse, enabling direct implementation of differential signaling, parity generation, or dual-edge interrupt logic without external inverters.
Is the CD74HC251MT pin-compatible with the 'LS251 TTL multiplexer?
No - the CD74HC251MT is not pin-compatible with the 'LS251. Only the HCT variant (e.g., CD74HCT251M96) is explicitly stated in the datasheet as speed-, function-, and pin-compatible with 'LS251. The HC version uses CMOS input thresholds and wider VCC range, requiring careful interface validation.
What is the maximum fanout capability of the CD74HC251MT?
The CD74HC251MT drives up to 10 LSTTL loads, as confirmed in the Features section and Electrical Characteristics tables of the datasheet. This fanout rating holds across the full –55 °C to 125 °C temperature range and is measured under standard load conditions (IOH = –6 mA, IOL = 6 mA at VCC = 4.5 V).
Can the CD74HC251MT be used in automotive under-hood applications?
Yes - the CD74HC251MT is rated for –55 °C to 125 °C operation and is manufactured using high-speed silicon-gate CMOS technology qualified for extended industrial environments. While not AEC-Q100 certified, its temperature range and robustness make it suitable for non-safety-critical under-hood functions like sensor multiplexing in engine control auxiliary modules.
CD74HC251MT 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:
- 5.2mA, 5.2mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
CD74HC251MT FAQ
1.How can I place an order for CD74HC251MT through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HC251MT 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 CD74HC251MT reliable?
The price and inventory of CD74HC251MT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HC251MT is usually 5 days.
3.What payment methods are accepted for CD74HC251MT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HC251MT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HC251MT?
CD74HC251MT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HC251MT 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 CD74HC251MT?
For technical support, including CD74HC251MT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HC251MT requirements.
6.How does Aetrix verify that CD74HC251MT is sourced from the original manufacturer or authorized distributors?
All CD74HC251MT 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 CD74HC251MT meets industry standards.
7.What is the process for return or replacement of CD74HC251MT?
All CD74HC251MT units undergo pre-shipment inspection (PSI). If there is an issue with CD74HC251MT, 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 CD74HC251MT part is unused and in its original packaging.
Return procedure for CD74HC251MT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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