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Texas Instruments SN74AHCT257PWR
- Part No.:
- SN74AHCT257PWR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
SN74AHCT257PWR.pdf
- Description:
- QUADRUPLE 2-LINE TO 1-LINE DATA
- Quantity:
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Product details
Overview
SN74AHCT257 from Texas Instruments is a quad 2-input data selector/multiplexer with three-state non-inverting outputs, operating at 4.5V–5.5V VCC, featuring TTL-compatible inputs, 6 ns typical propagation delay (25°C, 5V), ±25 mA output drive, and latch-up immunity exceeding 250 mA per JESD 17 - used for bus-oriented data routing in industrial control and digital instrumentation systems.
For engineers reviewing the SN74AHCT257 datasheet, SN74AHCT257 pinout, SN74AHCT257 application, or SN74AHCT257 equivalent, key selection criteria include its shared A/B select logic, active-low 3-state OE control, guaranteed operation across –40°C to +125°C, CMOS input compatibility with TTL voltage thresholds, and dual-package availability in TSSOP-16 and WQFN-16.
Technical Context
The SN74AHCT257 implements four independent 2:1 multiplexers sharing a common data-select (A/B) and output-enable (OE) input. Each channel routes either input A or B to its respective Y output based on the A/B logic level, while OE independently places all outputs into high-impedance state when asserted low.
Its balanced CMOS 3-state outputs support bidirectional bus interfacing with symmetrical sourcing/sinking capability (±8 mA at VCC = 5V), and TTL-compatible inputs accept VIH ≥ 2.0 V and VIL ≤ 0.8 V under recommended conditions - enabling direct connection to legacy TTL logic without level translation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - ensures compatibility with standard 5 V logic rails and tolerance against supply ripple. |
| Propagation Delay (tPLH/tPHL) | 6.4 ns typ (CL = 15 pF, 5 V) - enables high-speed data switching in synchronous bus architectures. |
| Output Drive (IOH/IOL) | ±8 mA at VCC = 5 V - sufficient to drive multiple CMOS loads or one TTL input without buffering. |
| Input Voltage Thresholds | VIH(min) = 2.0 V, VIL(max) = 0.8 V - guarantees reliable recognition of TTL-level signals across temperature. |
| Operating Temperature | –40°C to +125°C - supports deployment in automotive under-hood, industrial PLC, and harsh-environment embedded systems. |
| ESD Rating (HBM) | ±2000 V - meets JEDEC JS-001 for robustness during handling and board assembly. |
| Quiescent Current (ICC) | 40 µA max (VCC = 5.5 V) - minimizes static power in always-on control subsystems. |
Pinout & Package
SN74AHCT257PWR uses a 16-pin TSSOP (PW) package measuring 5 mm × 6.4 mm (body: 5 mm × 4.4 mm), with exposed thermal pad not present - suitable for standard surface-mount reflow and automated optical inspection.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B | Data inputs (per channel) | Eight dedicated inputs accepting two sources per multiplexer; electrically isolated but share select logic. |
| A/B | Global data-select control | Single logic line determining whether all channels pass A or B inputs - reduces PCB routing complexity. |
| 1Y, 2Y, 3Y, 4Y | Three-state outputs | Four buffered, non-inverting outputs capable of high-impedance state when OE is active low. |
| OE | Active-low output enable | Simultaneously disables all outputs to prevent bus contention - critical for multi-device shared-bus designs. |
| VCC | Positive supply | Primary 4.5–5.5 V power rail; must be decoupled locally with 0.1 µF capacitor per TI layout guidelines. |
| GND | Ground reference | Common return path for all I/O and supply currents; requires low-impedance plane for noise immunity. |
Key Features
| Feature | Design Value |
|---|---|
| TTL-Compatible Inputs | Accepts standard TTL voltage levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V) without external level shifters - simplifies mixed-logic system integration. |
| Balanced 3-State Outputs | Sources and sinks ±8 mA symmetrically, enabling clean bus driving and predictable termination behavior in shared-data-path applications. |
| Low Propagation Delay | 6.4 ns typical (CL = 15 pF) ensures minimal timing skew across all four channels - essential for synchronized multi-bit data selection. |
| Latch-Up Immunity | Exceeds 250 mA per JESD 17 - protects against destructive current surges during transient overvoltage events in industrial environments. |
| Wide Temperature Range | Rated from –40°C to +125°C - validated for continuous operation in automotive engine control units and factory automation controllers. |
Applications
| Industrial Bus Multiplexing | Digital Instrumentation Data Routing |
|---|---|
Use Scenario: Selecting between two sensor data streams (e.g., primary/backup pressure sensors) feeding a single ADC input in a programmable logic controller. IC Role / Device Role / Timing Role: Quad 2:1 multiplexer providing simultaneous 4-bit data path selection with deterministic 6.4 ns delay and bus-isolation via OE control. Use Value: Eliminates need for discrete logic gates or microcontroller-based switching, reducing BOM count and firmware overhead while maintaining real-time determinism. |
Use Scenario: Routing calibration coefficients from EEPROM or flash memory to DACs in a precision multimeter during self-test mode. IC Role / Device Role / Timing Role: Level-translating data selector enabling TTL-compatible memory readout into 5 V CMOS signal chain with no additional interface circuitry. Use Value: Ensures glitch-free coefficient loading by synchronizing all four bits via shared A/B and OE, preventing partial updates that could corrupt measurement accuracy. |
| Legacy System Interface Bridge | Configurable Logic Signal Steering |
Use Scenario: Interfacing a modern FPGA's 3.3 V I/O bank to legacy 5 V TTL peripherals using SN74AHCT257 as a direction-controlled data switch. IC Role / Device Role / Timing Role: Bidirectional bus buffer with 3-state outputs allowing FPGA to drive or sample TTL lines without contention. Use Value: Provides safe voltage-domain bridging without external resistors or translators, leveraging inherent TTL input compatibility and robust 5 V output swing. |
Use Scenario: Dynamically reconfiguring signal paths in test equipment - e.g., selecting between internal clock generator or external reference input for PLL lock detection circuitry. IC Role / Device Role / Timing Role: Four independent 2:1 selectors controlled by a single configuration bit (A/B), enabling compact, low-latency path switching. Use Value: Reduces PCB area and routing congestion versus discrete gate solutions while guaranteeing sub-10 ns path-to-path skew for timing-critical diagnostics. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar quad 2-input multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LV257APWR | Lower VCC range (2.0–5.5 V); higher VOL (0.55 V max at 8 mA) and slower tPLH (10.5 ns typ). | Supports mixed-voltage systems down to 2.0 V but sacrifices speed and noise margin vs. SN74AHCT257PWR. | Choose when interfacing with 2.5 V or 3.3 V logic and 5 V tolerance is unnecessary. |
| 74HC257PW,118 | Wider VCC (2.0–6.0 V); identical pinout; slightly higher IOL (±7.4 mA) and longer tPLH (14 ns typ at 4.5 V). | Offers broader supply flexibility but lacks guaranteed TTL input compatibility - may require pull-ups for marginal TTL drivers. | Prefer when operating outside 4.5–5.5 V range or when sourcing from NXP's long-lifecycle portfolio. |
Compared with SN74LV257APWR and 74HC257PW,118, the SN74AHCT257PWR delivers superior timing performance (6.4 ns vs. ≥10.5 ns), guaranteed TTL input recognition, and tighter VOL/VOL specs - making it optimal for high-speed, noise-sensitive 5 V bus applications where deterministic switching and legacy compatibility are mandatory.
Availability
SN74AHCT257PWR is available at Aetrix Electronics and suitable for industrial control, digital instrumentation, and legacy system interface applications requiring stable component supply, full -40°C to +125°C qualification, and long-term production continuity.
Supply support for SN74AHCT257PWR 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 experience delivering high-reliability components for industrial, automotive, and communications markets.
The SN74AHCT257 belongs to TI's advanced high-speed CMOS logic family, engineered specifically for robust 5 V bus interfacing, TTL compatibility, and seamless integration into mixed-signal control systems requiring deterministic data routing.
FAQ
What is the maximum capacitive load the SN74AHCT257PWR can drive while meeting all datasheet specifications?
The SN74AHCT257PWR is characterized and guaranteed to meet all switching and electrical specifications with a load capacitance of up to 50 pF, as confirmed in Section 5.6 Switching Characteristics and Section 8.3.1 Power Considerations. Driving larger capacitive loads may increase propagation delay and degrade edge integrity, though functionality is maintained beyond this limit - design verification is recommended for loads >50 pF.
Does the SN74AHCT257PWR support operation at 3.3 V supply voltage?
No, the SN74AHCT257PWR is not rated for 3.3 V operation. Its recommended operating VCC range is strictly 4.5 V to 5.5 V per Section 5.3, and absolute maximum ratings prohibit sustained operation below 4.5 V. For 3.3 V systems, consider the SN74LV257APWR or SN74LVC257APWR as functionally similar alternatives.
How does the shared A/B input affect channel independence in the SN74AHCT257PWR?
The shared A/B input means all four multiplexers simultaneously select either their A-input or B-input - individual per-channel selection is not supported. This architecture reduces control pin count and simplifies routing but requires both data sources to be valid and stable before asserting A/B, as confirmed in the Function Table (Section 7.4) and logic diagram (Figure 5-1).
Can unused inputs on the SN74AHCT257PWR be left floating?
No, unused inputs on the SN74AHCT257PWR must never be left floating. As stated in Section 7.3.2 and Section 8.7.1, TTL-compatible CMOS inputs require termination to VCC or GND to prevent undefined logic states, excessive power consumption, or oscillation. A 10 kΩ pull-up or pull-down resistor is recommended for intermittently driven inputs.
What is the purpose of the thermal pad in the SN74AHCT257PWR package?
The SN74AHCT257PWR uses a TSSOP-16 (PW) package, which does not include a thermal pad - only the WQFN-16 (BQB) variant (e.g., SN74AHCT257BQBR) features an exposed thermal pad. Therefore, the SN74AHCT257PWR relies solely on standard lead-frame conduction and PCB copper for thermal dissipation, with RθJA = 135.9 °C/W per Section 5.4.
SN74AHCT257PWR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Data Selector/Multiplexer
- Circuit:
- 4 x 2:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 8mA, 8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
SN74AHCT257PWR FAQ
1.How can I place an order for SN74AHCT257PWR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHCT257PWR 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 SN74AHCT257PWR reliable?
The price and inventory of SN74AHCT257PWR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHCT257PWR is usually 5 days.
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SN74AHCT257PWR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHCT257PWR 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 SN74AHCT257PWR?
For technical support, including SN74AHCT257PWR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHCT257PWR requirements.
6.How does Aetrix verify that SN74AHCT257PWR is sourced from the original manufacturer or authorized distributors?
All SN74AHCT257PWR 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 SN74AHCT257PWR meets industry standards.
7.What is the process for return or replacement of SN74AHCT257PWR?
All SN74AHCT257PWR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHCT257PWR, 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 SN74AHCT257PWR part is unused and in its original packaging.
Return procedure for SN74AHCT257PWR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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