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Texas Instruments SN74ALS257AN
- Part No.:
- SN74ALS257AN
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS257AN.pdf
- Description:
- IC MULTIPLEXER 4 X 2:1 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:302
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Product details
Overview
SN74ALS257AN from Texas Instruments is a quad 2-line-to-1-line data selector/multiplexer with 3-state outputs, designed for bus-organized systems. It features 4-bit multiplexing, output-enable (OE) control, and operates over 0°C to 70°C with 4.5–5.5 V supply. Used in high-performance digital systems where multiple data sources interface with a shared bus.
For engineers reviewing the SN74ALS257AN datasheet, SN74ALS257AN pinout, SN74ALS257AN application, or SN74ALS257AN equivalent, key selection criteria include propagation delay (tPLH/tPHL ≤10 ns), 3-state bus drive capability (IOL = 24 mA), logic family compatibility (ALS), and PDIP-16 package suitability for through-hole prototyping and legacy industrial control boards.
Technical Context
The SN74ALS257AN implements four independent 2:1 multiplexers sharing a common A/B select line and output-enable (OE) input. Each Y output is 3-state, disabling to high-impedance when OE is high - enabling direct connection to system buses without external isolation.
It uses advanced low-power Schottky (ALS) bipolar technology, delivering faster switching than standard TTL while maintaining compatible voltage thresholds (VIH = 2 V, VIL = 0.8 V) and fan-out capability. Its logic diagram confirms non-inverting data paths and synchronous enable control across all four channels.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | Advanced Low-Power Schottky (ALS) - ensures TTL-compatible operation with reduced power vs. standard LS, suitable for dense board layouts. |
| Supply Voltage | 4.5 V to 5.5 V - supports stable operation across standard 5 V rail tolerances without regulation overhead. |
| Propagation Delay | tPLH/tPHL ≤10 ns (VCC = 5 V, CL = 50 pF) - enables reliable timing in sub-25 MHz synchronous bus applications. |
| Output Drive | IOL = 24 mA / IOH = −2.6 mA - sufficient to drive 10+ standard TTL loads or terminate short PCB traces directly. |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade embedded systems, test equipment, and industrial controllers. |
| 3-State Enable Time | tPZL ≤18 ns, tPHZ ≤10 ns - guarantees fast bus arbitration and minimal contention window during output transitions. |
Pinout & Package
SN74ALS257AN is supplied in a 16-pin plastic dual in-line package (PDIP-N), 0.300-inch width, with standard through-hole footprint and JEDEC MS-001 compliant dimensions (19.18 mm × 6.67 mm).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A, 2A, 3A, 4A | Data Input A | First input of each 2:1 mux; selected when A/B = L. |
| 1B, 2B, 3B, 4B | Data Input B | Second input of each 2:1 mux; selected when A/B = H. |
| 1Y, 2Y, 3Y, 4Y | 3-State Output | Active-high multiplexed output; high-impedance when OE = H. |
| A/B | Select Control | Global 2:1 selection line for all four channels (L → A, H → B). |
| OE | Output Enable | Active-low enable; drives all Y outputs to Z-state when high. |
| VCC | Power Supply | +5 V supply pin (Pin 16); requires local 0.1 µF bypass to GND. |
| GND | Ground Reference | Signal and power return (Pin 8); must be low-inductance connection. |
Key Features
| Feature | Design Value |
|---|---|
| Bus-Interface Architecture | 3-state outputs eliminate need for external bus buffers, reducing component count and layout complexity in multi-source data routing. |
| ALS Logic Performance | Combines LS-speed (≤10 ns delay) with ALS power efficiency (~14 mA ICC disabled), extending thermal margin in compact assemblies. |
| Input/Output Compatibility | Full TTL-level DC specs (VIH = 2 V, VOL = 0.4 V @ 24 mA) ensure interoperability with 74LS, 74F, and microcontroller GPIOs. |
| Robust Absolute Ratings | Withstands 7 V VCC and VI, and 5.5 V on disabled outputs - enhances reliability during hot-swap or power sequencing events. |
Applications
| Industrial PLC I/O Expansion | Legacy Computer Bus Arbitration |
|---|---|
Use Scenario: Adding discrete sensor inputs to a programmable logic controller via shared backplane data bus. IC Role / Device Role / Timing Role: Data selector routing analog-to-digital converter outputs or switch status signals onto the main data bus under CPU address decode control. Use Value: Enables 4-channel signal consolidation per IC with deterministic 10 ns propagation, minimizing scan cycle jitter in real-time control loops. | Use Scenario: Managing access to a shared memory/data bus among multiple peripheral cards in an ISA-style industrial computer. IC Role / Device Role / Timing Role: Bus multiplexer isolating DMA controller, UART, and timer outputs onto one bidirectional data path using OE and A/B coordination. Use Value: Eliminates contention risk via hardware-enforced 3-state disable, supporting reliable 8-bit parallel transfers at up to 8 MHz clock rates. |
| Test Equipment Signal Routing | Digital Instrumentation Multiplexing |
Use Scenario: Configurable signal path selection in automated test fixtures for validating mixed-signal PCBs. IC Role / Device Role / Timing Role: Channel selector directing DUT stimulus signals (e.g., clock, reset, serial commands) from pattern generator to target pins. Use Value: Provides repeatable, low-skew routing (≤12 ns max skew between Y outputs) critical for timing-sensitive functional tests. | Use Scenario: Consolidating front-panel switch inputs or calibration DAC outputs into a single microcontroller interface in benchtop meters. IC Role / Device Role / Timing Role: Input multiplexer feeding 4-bit configuration data (e.g., range, filter mode, display format) to MCU GPIO or ADC auxiliary channel. Use Value: Reduces required MCU pins by 75% versus discrete inputs while maintaining direct logic-level compatibility and no software overhead. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar data selector applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS258AN | Inverts output polarity (Y = A̅·A/B + B̅·Ā/B); otherwise identical pinout, timing, and drive strength. | Suitable only where inverted logic is acceptable or compensated in firmware; not drop-in for non-inverting signal paths. | Select SN74ALS258AN only if system design explicitly requires active-low output behavior. |
| SN74AS257N | Faster propagation (tPLH/tPHL ≤6 ns), higher drive (IOL = 48 mA), but increased ICC (up to 31.9 mA) and tighter VIH (2.0 V min). | Better for high-speed bus designs (>12 MHz), but requires stricter noise margin management and thermal derating. | Choose SN74AS257N when speed outweighs power budget constraints and board-level noise is controlled. |
Compared with SN74ALS257AN, SN74ALS258AN provides inverted outputs without changing timing or packaging, while SN74AS257N delivers 40% lower propagation delay at the cost of doubled quiescent current - making SN74ALS257AN optimal for balanced speed/power trade-offs in commercial-grade control systems.
Availability
SN74ALS257AN is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy computer bus arbitration, and digital instrumentation multiplexing requiring stable component supply and long-term obsolescence support.
Supply support for SN74ALS257AN 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS257AN belongs to TI's legacy 74ALS logic family, engineered for high-reliability commercial systems where robustness, predictable timing, and backward compatibility with TTL infrastructure are essential.
FAQ
What is the maximum clock frequency supported by SN74ALS257AN in a synchronous bus application?
The SN74ALS257AN does not operate on a clock; it is combinatorial logic. Its maximum usable data rate depends on propagation delay and system setup/hold timing. With tPHL/tPLH ≤10 ns and typical bus loading, SN74ALS257AN reliably supports data valid windows consistent with 25 MHz system clocks in well-designed PCB layouts with controlled trace impedance and proper termination.
Can SN74ALS257AN drive standard TTL loads directly without buffer amplification?
Yes. SN74ALS257AN can drive up to 10 standard TTL unit loads (IOL = 24 mA, IOH = −2.6 mA) directly. Its VOL = 0.4 V at 24 mA and VOH = 2.4 V at −2.6 mA meet TTL input thresholds, enabling direct interconnection with 74LS, 74F, and legacy microprocessor data buses without intermediate drivers.
Is SN74ALS257AN RoHS compliant and lead-free?
Yes. SN74ALS257AN is RoHS compliant with lead-free (NIPDAU) terminal finish, as confirmed in TI's official packaging addendum. It meets EU Directive 2011/65/EU requirements and carries no exemptions - suitable for new designs targeting global environmental compliance.
How does the output-enable (OE) pin behave electrically on SN74ALS257AN?
The OE pin on SN74ALS257AN is active-low: outputs go to high-impedance (3-state) when OE is high (≥2 V), and normal multiplexed operation occurs when OE is low (≤0.8 V). Its input leakage is ±0.1 mA max, and it exhibits standard TTL-compatible thresholds - allowing direct connection to microcontroller GPIOs or open-collector bus lines.
What is the thermal performance of SN74ALS257AN in a PDIP package at full load?
In the PDIP-16 package, SN74ALS257AN has a maximum power dissipation of 1.1 W at TA = 55°C (still air). At worst-case ICC = 14 mA and VCC = 5.5 V, power consumption is ~77 mW - well within thermal limits. No heatsink is required; standard 1 oz copper pour around GND/VCC pins suffices for continuous operation at 70°C ambient.
SN74ALS257AN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Bulk
- Product Status:
- Active
- Type:
- Multiplexer
- Circuit:
- 4 x 2:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 2.6mA, 24mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
SN74ALS257AN FAQ
1.How can I place an order for SN74ALS257AN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS257AN 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 SN74ALS257AN reliable?
The price and inventory of SN74ALS257AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS257AN is usually 5 days.
3.What payment methods are accepted for SN74ALS257AN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS257AN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS257AN?
SN74ALS257AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS257AN 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 SN74ALS257AN?
For technical support, including SN74ALS257AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS257AN requirements.
6.How does Aetrix verify that SN74ALS257AN is sourced from the original manufacturer or authorized distributors?
All SN74ALS257AN 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 SN74ALS257AN meets industry standards.
7.What is the process for return or replacement of SN74ALS257AN?
All SN74ALS257AN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS257AN, 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 SN74ALS257AN part is unused and in its original packaging.
Return procedure for SN74ALS257AN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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