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Texas Instruments SN74LS257BDR
- Part No.:
- SN74LS257BDR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS257BDR.pdf
- Description:
- IC MULTIPLEXER 4 X 2:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,475
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Product details
Overview
SN74LS257BDR from Texas Instruments is a quadruple 2-line to 1-line data selector/multiplexer in SOIC-16 package, operating over 0°C to 70°C, with typical propagation delay of 15 ns at VCC = 5 V, fan-out of 20 LSTTL loads, and compatible with standard LS logic levels. It routes four independent 2-input data pairs to a common output under dual select control, used in digital bus management and address/data path switching.
For engineers reviewing the SN74LS257BDR datasheet, SN74LS257BDR pinout, SN74LS257BDR application, or SN74LS257BDR equivalent, this page delivers verified electrical parameters, validated pin functions, confirmed industrial use cases, and two technically documented alternative parts for legacy TTL system design and replacement planning.
Technical Context
The SN74LS257BDR implements four independent 2:1 multiplexers sharing common select (S) and enable (G̅) inputs. Each channel selects between I0A/I0B or I1A/I1B based on S state, with active-low enable gating all outputs to high-impedance when asserted.
It uses bipolar Schottky TTL technology, delivering guaranteed 15 ns max propagation delay (tPLH/tPHL), 2.4 V min high-level output voltage (VOH), and –0.5 V max low-level input voltage (VIL) across full temperature range - ensuring interoperability with legacy 74LS and 74L series logic families.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Quadruple 2-line to 1-line data selector/multiplexer - enables parallel selection of four independent 2-input data paths |
| Logic Family | 74LS (Low-power Schottky TTL) - ensures compatibility with industry-standard LS logic voltage thresholds and drive strength |
| Propagation Delay | 15 ns max (tPLH/tPHL at VCC = 5 V, TA = 25°C) - supports reliable operation in 33 MHz synchronous systems |
| Supply Voltage | 4.75 V to 5.25 V - matches regulated 5 V TTL rails without external regulation |
| Operating Temperature | 0°C to 70°C - certified for commercial-grade embedded control and instrumentation applications |
| Output Drive | 20 LSTTL loads - sufficient to drive multiple downstream LS inputs without buffering |
| Package | SOIC-16 (D), RoHS-compliant, NIPDAU lead finish - surface-mount compatible with automated assembly and IPC-7351 land patterns |
Pinout & Package
SN74LS257BDR is housed in a 16-pin SOIC (D) package measuring 10.4 mm × 5.3 mm × 2.0 mm max height, with 1.27 mm pitch, gull-wing leads, and pin 1 identifier in quadrant Q1 per tape-and-reel orientation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 4, 5, 9, 10, 12, 13 | Data Inputs (I0A, I1A, I0B, I1B, I0C, I1C, I0D, I1D) | Eight independent data inputs grouped as four 2-input pairs - each pair feeds one multiplexer channel |
| 3, 11 | Select Inputs (S) | Common select line controlling all four multiplexers simultaneously - low selects I0x, high selects I1x |
| 6, 7, 8, 14 | Outputs (YA, YB, YC, YD) | Four buffered, non-inverted outputs - each reflects selected input of its respective channel |
| 15 | Enable (G̅) | Active-low global enable - asserts high-impedance state on all outputs when logic high |
| 16 | VCC | Positive supply terminal - requires stable 5 V ±5% source with local 0.1 µF bypassing |
| 8 | GND | Ground reference - shared return for all channels; must be low-inductance connection |
Key Features
| Feature | Design Value |
|---|---|
| Independent Channel Operation | Four fully isolated 2:1 multiplexers share only S and G̅ - enables simultaneous but distinct data routing decisions per channel |
| High Noise Immunity | Input noise margin ≥0.4 V at VCC = 5 V - suppresses false triggering in electrically noisy industrial environments |
| Three-State Outputs | Outputs enter high-impedance state when G̅ = HIGH - allows direct connection to shared buses without contention |
| Standard Pin Compatibility | Pinout matches industry-standard 74LS257 footprint - enables drop-in replacement in existing PCB layouts |
| RoHS-Compliant Packaging | SOIC-D with NIPDAU finish and Level-1 MSL rating - supports lead-free reflow (260°C peak) and long-term supply chain compliance |
Applications
| Microprocessor Address Decoding | Legacy Bus Arbitration |
|---|---|
Use Scenario: Selecting between alternate memory-mapped peripheral addresses during CPU read/write cycles in 8-bit microcontroller systems. IC Role / Device Role / Timing Role: SN74LS257BDR acts as address-path selector, routing A0–A15 lines to either ROM or RAM banks based on chip-select logic timing. Use Value: Eliminates need for discrete gate logic or PLD programming - reduces BOM count and layout complexity while maintaining cycle-accurate timing. | Use Scenario: Managing shared data bus access among multiple legacy peripherals (e.g., UART, ADC, DAC) in an ISA-style backplane architecture. IC Role / Device Role / Timing Role: SN74LS257BDR serves as bidirectional bus switch controller, enabling time-multiplexed data transfer with precise enable/selection edge alignment. Use Value: Provides deterministic 15 ns propagation delay and three-state isolation - prevents bus contention and signal corruption during arbitration transitions. |
| Digital Test Equipment Signal Routing | Industrial Control Logic Expansion |
Use Scenario: Configuring stimulus/sense paths in automated test equipment (ATE) where multiple DUT interfaces require dynamic signal path reconfiguration. IC Role / Device Role / Timing Role: SN74LS257BDR functions as programmable signal router, controlled by FPGA GPIOs to establish real-time analog/digital signal chains. Use Value: Delivers guaranteed 20 LSTTL fan-out and 2.4 V VOH - ensures robust signal integrity across long PCB traces in modular test fixtures. | Use Scenario: Extending discrete I/O capability in PLC modules where field sensor inputs must be dynamically assigned to processing channels. IC Role / Device Role / Timing Role: SN74LS257BDR operates as configurable input selector, mapping eight sensor signals into four processing lanes under ladder logic control. Use Value: Supports 0°C to 70°C operation and high noise immunity - maintains reliability in factory-floor environments with EMI from motors and relays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 2:1 multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS258BDR | Inverts outputs (Y = NOT(IS)); identical pinout, timing, and DC specs | Required where inverted output polarity is needed - e.g., active-low enable logic or complemented bus signaling | Select SN74LS258BDR only when inversion is functionally required; otherwise SN74LS257BDR provides non-inverting behavior with identical footprint. |
| SN74LS157N | Same function and pinout, but in PDIP-16 package; 0°C to 70°C, same AC/DC specs | Used in through-hole prototyping, legacy repair, or mixed-technology boards requiring socketed devices | Choose SN74LS157N for hand-soldered development or field replacement where SOIC rework is impractical; SN74LS257BDR preferred for volume SMT production. |
Compared with SN74LS258BDR and SN74LS157N, the SN74LS257BDR offers non-inverting output logic in a RoHS-compliant SOIC package optimized for automated assembly - making it the default choice for new commercial designs requiring standard TTL multiplexing without polarity inversion or through-hole mounting.
Availability
SN74LS257BDR is available at Aetrix Electronics and suitable for microprocessor address decoding, legacy bus arbitration, digital test equipment signal routing, and industrial control logic expansion requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74LS257BDR 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 U.S.-based semiconductor company founded in 1930, specializing in analog and embedded processing technologies with broad industrial, automotive, and consumer product portfolios.
The SN74LS257BDR belongs to TI's legacy 74LS logic family, designed specifically for backward-compatible TTL system upgrades, board-level repair, and cost-sensitive industrial control applications where reliability and second-source availability are critical.
FAQ
What is the maximum clock frequency supported by SN74LS257BDR?
The SN74LS257BDR is not a clocked device and has no internal clock - it operates asynchronously. Its usable data rate is limited by propagation delay (15 ns max) and setup/hold times. For clean switching, input changes should be stable ≥20 ns before and after the effective selection edge, supporting reliable operation up to approximately 33 MHz in well-designed systems using the SN74LS257BDR.
Does SN74LS257BDR support 3.3 V logic interfacing?
No - the SN74LS257BDR is a 5 V-only TTL device requiring VCC = 4.75–5.25 V. Its input thresholds (VIL ≤ –0.5 V, VIH ≥ 2.0 V) and output levels (VOL ≤ 0.5 V, VOH ≥ 2.4 V) are incompatible with 3.3 V CMOS logic without level translation. Direct connection to 3.3 V systems may cause undefined states or excessive current draw in the SN74LS257BDR.
Is SN74LS257BDR pin-compatible with SN74LS157?
Yes - the SN74LS257BDR and SN74LS157 share identical pin assignments, electrical specifications, and functional behavior. Both are quadruple 2:1 non-inverting multiplexers with common select and enable. The SN74LS257BDR replaces SN74LS157 in SOIC packaging, while SN74LS157 is typically offered in PDIP. Designers can substitute SN74LS257BDR for SN74LS157 in new layouts without modification.
What is the power dissipation of SN74LS257BDR under typical operation?
The SN74LS257BDR draws 19 mA typical supply current (ICC) at VCC = 5 V and 25°C with all outputs loaded. At worst-case (all outputs switching, max temperature), ICC reaches 32 mA, yielding ~160 mW max power dissipation. This allows safe operation in dense SOIC layouts without forced airflow or heatsinking when ambient temperature remains ≤70°C.
Can SN74LS257BDR outputs drive LEDs directly?
No - SN74LS257BDR outputs are rated for 20 LSTTL loads (≈0.4 mA sink/source per output), insufficient to drive standard 2–20 mA LEDs. Attempting direct LED drive risks exceeding output current limits, causing voltage droop, timing skew, or permanent damage. Use a dedicated driver transistor or buffer IC (e.g., ULN2003) when interfacing with LEDs using the SN74LS257BDR.
SN74LS257BDR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74LS257BDR FAQ
1.How can I place an order for SN74LS257BDR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS257BDR 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 SN74LS257BDR reliable?
The price and inventory of SN74LS257BDR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS257BDR is usually 5 days.
3.What payment methods are accepted for SN74LS257BDR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS257BDR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS257BDR?
SN74LS257BDR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS257BDR 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 SN74LS257BDR?
For technical support, including SN74LS257BDR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS257BDR requirements.
6.How does Aetrix verify that SN74LS257BDR is sourced from the original manufacturer or authorized distributors?
All SN74LS257BDR 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 SN74LS257BDR meets industry standards.
7.What is the process for return or replacement of SN74LS257BDR?
All SN74LS257BDR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS257BDR, 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 SN74LS257BDR part is unused and in its original packaging.
Return procedure for SN74LS257BDR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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