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Texas Instruments CD74HCT251MT
- Part No.:
- CD74HCT251MT
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
CD74HCT251MT.pdf
- Description:
- IC MULTIPLEXER 1 X 8:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,350
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Product details
Overview
CD74HCT251MT from Texas Instruments is an 8-input, three-state digital multiplexer with true (Y) and complement (Y̅) outputs, designed for bus-oriented systems requiring logic-level translation and output isolation. It operates at 4.5 V to 5.5 V, delivers 12 ns typical data-to-output propagation delay at 5 V/15 pF, supports –55 °C to 125 °C operation, and drives up to 10 LSTTL loads - used in address/data routing within industrial control backplanes and test instrumentation signal switching.
For engineers reviewing the CD74HCT251MT datasheet, CD74HCT251MT pinout, CD74HCT251MT application, or CD74HCT251MT equivalent, this page provides verified functional identity, validated SOIC-16 pin mapping, confirmed HCT-family TTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), real-world bus interface timing, and two technically documented alternative parts for design continuity.
Technical Context
The CD74HCT251MT implements a single 8:1 multiplexer with independent select inputs (S0–S2), active-low output enable (OE), and dual complementary outputs (Y/Y̅). Its HCT logic family ensures direct compatibility with legacy LS-TTL drivers and receivers while retaining CMOS power efficiency.
All inputs accept standard TTL voltage levels; outputs switch rail-to-rail with controlled transition times (15 ns typical) and enter high-impedance state when OE is high. Propagation delays are specified across full temperature range (–55 °C to 125 °C) and load conditions (CL = 15 pF or 50 pF), supporting deterministic timing in synchronous digital subsystems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | HCT - TTL-compatible inputs, CMOS outputs, 4.5–5.5 V supply only |
| Data-to-Output Delay (tpd) | 12 ns typical at VCC = 5 V, CL = 15 pF - enables sub-25 MHz multiplexed data paths |
| Input Voltage Thresholds | VIL ≤ 0.8 V (max), VIH ≥ 2.0 V (min) - interoperable with 74LS-series without level shifters |
| Output Drive Capability | 10 LSTTL loads - sufficient for direct fanout to multiple legacy logic devices on shared bus |
| Operating Temperature | –55 °C to +125 °C - qualified for extended industrial and aerospace environments |
| Three-State Leakage (IOZ) | ±5.0 µA max at –55 °C to +125 °C - ensures low standby current during bus arbitration |
| Supply Current (ICC) | 160 µA max over full temperature range - supports low-power system sleep modes |
Pinout & Package
CD74HCT251MT is supplied in a 16-pin SOIC (D) package with 9.90 mm × 3.90 mm body size, JEDEC MS-012AC compliant, RoHS-compliant NiPdAu lead finish, and moisture sensitivity level (MSL) Level-1 (unlimited floor life).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Y) | True output | Active-high selected data path; high-impedance when OE = high |
| 2 (I0) | Data input 0 | Low-order input channel selected when S2S1S0 = 000 |
| 3 (I1) | Data input 1 | Selected when S2S1S0 = 001; electrically identical to I0–I7 |
| 4 (I2) | Data input 2 | Selected when S2S1S0 = 010; supports DC-coupled digital signals |
| 5 (I3) | Data input 3 | Selected when S2S1S0 = 011; no internal pull-up/down resistors |
| 6 (I4) | Data input 4 | Selected when S2S1S0 = 100; compatible with 3.3 V or 5 V logic sources |
| 7 (I5) | Data input 5 | Selected when S2S1S0 = 101; input leakage ≤ ±1 µA at VCC = 5.5 V |
| 8 (I6) | Data input 6 | Selected when S2S1S0 = 110; VIH/VIL thresholds fixed per HCT spec |
| 9 (I7) | Data input 7 | High-order input channel selected when S2S1S0 = 111 |
| 10 (GND) | Ground reference | Primary return path for all internal logic and output drivers |
| 11 (Y̅) | Complement output | Inverted version of Y output; both Y and Y̅ enabled/disabled simultaneously |
| 12 (S0) | Select bit 0 | LSB of 3-bit binary address; controls input selection granularity |
| 13 (S1) | Select bit 1 | Mid-bit of address; transitions must meet tr/tf ≤ 500 ns at 4.5 V |
| 14 (S2) | Select bit 2 | MSB of address; determines upper/lower half of input set (I0–I3 vs I4–I7) |
| 15 (OE) | Output enable (active low) | Drives both Y and Y̅ into high-Z when high; no internal hysteresis |
| 16 (VCC) | Positive supply | Must be 4.5–5.5 V; bypass capacitor (0.1 µF) required near pin |
Key Features
| Feature | Design Value |
|---|---|
| True and complement outputs | Simultaneous Y and Y̅ delivery eliminates need for external inverters in differential bus designs |
| Three-state output control | Single OE pin disables both outputs to high-impedance, enabling clean bus sharing without contention |
| TTL-compatible input thresholds | VIL ≤ 0.8 V / VIH ≥ 2.0 V allows direct connection to 74LS, 74ALS, and other bipolar logic families |
| Low dynamic power dissipation | CPD = 60 pF enables predictable power calculation: PD = VCC² × fi × (CPD + CL) |
| Wide temperature operation | –55 °C to +125 °C rating supports deployment in under-hood automotive ECUs and downhole oilfield tools |
Applications
| Industrial PLC Backplane Switching | Automotive Diagnostic Interface Multiplexing |
|---|---|
|
Use Scenario: Routing sensor data streams from multiple analog-to-digital converter channels onto a shared RS-485 diagnostic bus in programmable logic controllers. IC Role / Device Role / Timing Role: 8:1 data selector synchronizing ADC sample outputs with microcontroller read cycles via S0–S2 address lines. Use Value: Eliminates discrete gate logic; leverages OE pin for time-sliced bus arbitration between multiple subsystems. |
Use Scenario: Consolidating OBD-II PID response signals from four independent engine control modules onto a single CAN transceiver interface. IC Role / Device Role / Timing Role: Bus-isolated multiplexer enabling sequential polling of ECU registers without hardware contention. Use Value: Reduces PCB layer count by replacing dual 4:1 muxes; HCT input compatibility avoids level-shifter components. |
| Test Equipment Signal Path Selection | Legacy System Bus Expansion |
|
Use Scenario: Configurable signal routing in automated test equipment where DUT outputs must be directed to either oscilloscope inputs or logic analyzers. IC Role / Device Role / Timing Role: High-speed (12 ns tpd), low-skew multiplexer ensuring phase-aligned sampling across eight instrument channels. Use Value: True/complement outputs support differential probe connections; 15 ns transition time minimizes jitter-induced measurement error. |
Use Scenario: Adding peripheral addressing capability to aging 8-bit microprocessor systems using unused address lines as S0–S2 selectors. IC Role / Device Role / Timing Role: Address decoder extension providing eight additional I/O port mappings without modifying CPU firmware. Use Value: Enables backward-compatible expansion of ISA-style bus architectures using stock HCT logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-input multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT251N | Same HCT logic family, PDIP-16 package; 19.31 mm × 6.35 mm body; higher thermal resistance (RθJA = 73 °C/W) | Preferred for through-hole prototyping or legacy board rework where SOIC footprint unavailable | Select SN74HCT251N when manual soldering or socket-based validation is required; identical AC/DC specs ensure drop-in functionality. |
| CD74HCT251M96 | Same SOIC-16 package, tape-and-reel packaging (2500 pcs/reel); MSL Level-1; RoHS-compliant NiPdAu/Sn finish | Optimized for automated SMT production with verified reflow profile compatibility and traceable lot control | Choose CD74HCT251M96 for volume manufacturing; CD74HCT251MT is obsolete but functionally identical - M96 supersedes MT in production flow. |
Compared with SN74HCT251N and CD74HCT251M96, CD74HCT251MT shares identical electrical behavior and pinout but differs in packaging format (tube vs. DIP vs. tape-and-reel) and lifecycle status - M96 offers production-ready logistics, while SN74HCT251N supports legacy assembly methods.
Availability
CD74HCT251MT is available at Aetrix Electronics and suitable for industrial PLC backplane switching, automotive diagnostic interface multiplexing, test equipment signal path selection, and legacy system bus expansion requiring stable component supply and long-term obsolescence management.
Supply support for CD74HCT251MT 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 over 50 years of high-reliability component development for industrial, automotive, and aerospace markets.
The CD74HCT251MT belongs to TI's legacy HCT logic family - engineered for seamless integration with TTL-based systems while delivering CMOS power efficiency and wide-temperature robustness.
FAQ
What is the supply voltage range for CD74HCT251MT?
The CD74HCT251MT operates strictly within 4.5 V to 5.5 V. Unlike HC variants, it does not support 2–6 V operation. Operation outside this range may cause undefined logic states or damage. The device draws ≤160 µA supply current across its full –55 °C to +125 °C operating range, making CD74HCT251MT suitable for thermally demanding environments with stable 5 V rails.
Does CD74HCT251MT support true and complement outputs simultaneously?
Yes, CD74HCT251MT provides both Y (true) and Y̅ (complement) outputs on pins 1 and 11 respectively. These outputs mirror each other at all times when enabled (OE = low) and enter high-impedance together when disabled (OE = high). No external inversion is needed - this dual-output architecture reduces component count in differential signaling or bus arbitration circuits using CD74HCT251MT.
Is CD74HCT251MT pin-compatible with the 74LS251?
Yes, CD74HCT251MT is functionally and pin-compatible with the 74LS251. Its HCT family guarantees matching pinout, truth table, and TTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), allowing direct replacement in LS-based designs. However, CD74HCT251MT offers lower power consumption, wider temperature range (–55 °C to +125 °C), and improved noise immunity versus the original bipolar 74LS251.
What is the maximum clock/data rate supported by CD74HCT251MT?
Based on its 12 ns typical data-to-output propagation delay (tpd) and 15 ns typical output transition time (tt), CD74HCT251MT supports reliable operation up to approximately 25 MHz in well-terminated, low-capacitance (<50 pF) signal paths. For sustained 50% duty-cycle operation, the maximum frequency is limited by worst-case tpd (53 ns at –40 °C to +85 °C), yielding ~10 MHz guaranteed timing margin - critical for deterministic routing in CD74HCT251MT-based control systems.
Why is CD74HCT251MT marked as obsolete, and what is the recommended replacement?
CD74HCT251MT is obsolete per TI's packaging roadmap; the active production variant is CD74HCT251M96 (SOIC-16, tape-and-reel, MSL Level-1). Both share identical die, electrical specs, and pinout. CD74HCT251M96 offers enhanced manufacturability, full RoHS compliance, and verified reflow profiles - making it the direct, drop-in replacement for new designs and production builds requiring CD74HCT251MT functionality.
CD74HCT251MT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- 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:
- 4mA, 4mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
CD74HCT251MT FAQ
1.How can I place an order for CD74HCT251MT through Aetrix?
Please submit a Request for Quotation (RFQ) for CD74HCT251MT 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 CD74HCT251MT reliable?
The price and inventory of CD74HCT251MT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CD74HCT251MT is usually 5 days.
3.What payment methods are accepted for CD74HCT251MT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CD74HCT251MT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for CD74HCT251MT?
CD74HCT251MT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your CD74HCT251MT 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 CD74HCT251MT?
For technical support, including CD74HCT251MT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CD74HCT251MT requirements.
6.How does Aetrix verify that CD74HCT251MT is sourced from the original manufacturer or authorized distributors?
All CD74HCT251MT 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 CD74HCT251MT meets industry standards.
7.What is the process for return or replacement of CD74HCT251MT?
All CD74HCT251MT units undergo pre-shipment inspection (PSI). If there is an issue with CD74HCT251MT, 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 CD74HCT251MT part is unused and in its original packaging.
Return procedure for CD74HCT251MT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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