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Texas Instruments SN74ALS157AN
- Part No.:
- SN74ALS157AN
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS157AN.pdf
- Description:
- IC MULTIPLEXER 4 X 2:1 16DIP
- Quantity:
- Payment:
- Shipping:
Inventory:464
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Product details
Overview
SN74ALS157AN from Texas Instruments is a quad 2-line-to-1-line data selector/multiplexer IC in a 16-pin plastic DIP (N) package, operating from 4.5 V to 5.5 V at 0°C to 70°C. It routes one of two 4-bit input sources to four outputs under control of a common strobe (G) and select (A/B) inputs, presenting true (non-inverted) data with typical propagation delays of 9 ns (A/B→Y) and 14 ns (G→Y) at 5 V.
For engineers reviewing the SN74ALS157AN datasheet, SN74ALS157AN pinout, SN74ALS157AN application, or SN74ALS157AN equivalent, this device serves as a TTL-compatible logic-level multiplexer for bus selection, signal routing, and address/data path switching in legacy industrial controllers, test equipment, and retro-computing systems where ALS family speed-power trade-offs are specified.
Technical Context
The SN74ALS157AN implements four independent 2:1 multiplexers sharing a single A/B select line and a common enable (G) input. Each output stage includes buffered drivers capable of sourcing −0.4 mA and sinking 4 mA at VOH = VCC − 2 V and VOL = 0.25 V (IOL = 4 mA).
It belongs to the advanced low-power Schottky (ALS) logic family, delivering improved speed over standard LS while maintaining compatible input thresholds (VIH = 2 V, VIL = 0.8 V) and output drive. Its 16-pin PDIP package supports through-hole mounting and legacy board repair or prototyping.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Compatible with standard +5 V TTL supply rails; no external regulation required. |
| Propagation Delay (A/B → Y) | 4–14 ns max - Enables reliable operation in synchronous digital systems up to ~35 MHz clock-equivalent rates. |
| Output Drive (IOL) | 4 mA - Sufficient to directly drive multiple LS-TTL inputs (fan-out ≥ 20) without buffering. |
| Input Thresholds | VIL ≤ 0.8 V, VIH ≥ 2.0 V - Ensures robust noise margin against TTL-level signals and compatibility with 74LS/74F families. |
| Operating Temperature | 0°C to 70°C - Rated for commercial-grade applications including office equipment, instrumentation, and non-automotive embedded systems. |
| ICC (Quiescent Current) | 6–11 mA - Low static power consumption relative to standard TTL, reducing thermal load in dense logic designs. |
Pinout & Package
SN74ALS157AN uses a 16-pin plastic dual in-line package (PDIP-N), 300-mil width, with 0.1-inch lead pitch. Pin 1 is marked by a notch or dot at the top-left corner when viewed from the top with pins facing down.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A, 2A, 3A, 4A | Data Input A (Source 1) | Four independent inputs selected when A/B = L; routed to corresponding Y outputs if G = L. |
| 1B, 2B, 3B, 4B | Data Input B (Source 2) | Four independent inputs selected when A/B = H; routed to corresponding Y outputs if G = L. |
| 1Y, 2Y, 3Y, 4Y | Output (True Data) | Active-high, non-inverting outputs; high-impedance state only when G = H (strobe disabled). |
| A/B | Select Control | Global 2:1 source selector: L selects A inputs, H selects B inputs across all four channels. |
| G | Strobe Enable | Active-low enable: outputs valid only when G = L; outputs high-impedance when G = H. |
| VCC (Pin 16) | Power Supply | +5 V supply connection; decoupling capacitor recommended near pin for noise suppression. |
| GND (Pin 8) | Ground Reference | Logic and power ground return; must be low-impedance connection to minimize switching noise. |
Key Features
| Feature | Design Value |
|---|---|
| True-data output logic | Delivers non-inverted outputs - eliminates need for external inverters in data-path alignment. |
| Buffered inputs and outputs | Reduces loading on upstream drivers and improves noise immunity in multi-load configurations. |
| Common strobe (G) and select (A/B) | Enables synchronized 4-bit word selection with minimal control wiring - ideal for bus arbitration. |
| ALS family performance | Combines 33% lower power than standard TTL with 2× faster speed than 74LS - optimized for legacy system upgrades. |
| PDIP-16 packaging | Supports hand-soldering, socket-based prototyping, and field-replaceable logic in maintenance-critical systems. |
Applications
| Industrial PLC I/O Expansion | Legacy Test Equipment Signal Routing |
|---|---|
|
Use Scenario: Expanding discrete input/output capacity in programmable logic controllers using shared address/data buses. IC Role / Device Role / Timing Role: Quad 2:1 multiplexer selecting between primary and backup sensor banks or actuator sets under CPU control. Use Value: Reduces PCB real estate and control-line count versus discrete gates; maintains deterministic timing with sub-15 ns propagation delay. |
Use Scenario: Switching calibration reference signals or stimulus paths in automated test equipment (ATE) racks. IC Role / Device Role / Timing Role: Signal path selector enabling dynamic reconfiguration of analog/digital stimulus without manual patching. Use Value: Provides TTL-compatible level-shifting and fan-out capability for driving multiple instrument inputs simultaneously. |
| Retrocomputing System Bus Arbitration | Embedded Diagnostic Interface Multiplexing |
|
Use Scenario: Managing memory-mapped peripheral access in 8-bit microcomputer systems (e.g., Z80, 6502) with limited address lines. IC Role / Device Role / Timing Role: Address decoder auxiliary for selecting between ROM, RAM, or I/O space based on upper address bits and chip-enable strobes. Use Value: Delivers predictable setup/hold timing and direct compatibility with vintage TTL logic families used in restoration projects. |
Use Scenario: Consolidating diagnostic port signals (UART, JTAG, SPI) onto a single debug header in space-constrained embedded modules. IC Role / Device Role / Timing Role: Logic-level multiplexer enabling software-selectable interface routing during factory test or field service. Use Value: Eliminates mechanical switches or jumpers; supports hot-swappable diagnostics without hardware modification. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar data selector applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS157ADR | SOIC-16 package; same electrical specs; RoHS-compliant NiPdAu finish; MSL Level-1. | Suitable for surface-mount production; requires reflow soldering and PCB layout revision. | Select when migrating from through-hole to automated assembly; verify thermal pad clearance and trace routing. |
| SN74AS157N | Faster propagation (1–6 ns vs. 4–14 ns); higher ICC (17.5–28 mA); same pinout and function. | Better suited for high-speed timing-critical paths but increases power dissipation and EMI risk. | Choose only if sub-10 ns delay is mandatory and power/thermal budget allows; verify signal integrity margins. |
Compared with SN74ALS157ADR and SN74AS157N, the SN74ALS157AN offers optimal balance of legacy compatibility, through-hole serviceability, and ALS-family power efficiency - making it the preferred choice for repair, prototyping, and commercial-grade systems where speed beyond 35 MHz is unnecessary.
Availability
SN74ALS157AN is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy test equipment signal routing, and retrocomputing system bus arbitration requiring stable component supply and long-term obsolescence management.
Supply support for SN74ALS157AN 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 with broad industrial and automotive qualification.
The SN74ALS157AN belongs to TI's legacy TTL logic portfolio, designed specifically for backward-compatible upgrades and maintenance of commercial-grade digital systems requiring proven reliability and wide temperature tolerance.
FAQ
What logic family does SN74ALS157AN belong to, and how does it compare to standard TTL?
SN74ALS157AN belongs to the Advanced Low-Power Schottky (ALS) logic family. It delivers approximately twice the speed and one-third the power consumption of standard 74TTL, while maintaining full pin and functional compatibility with 74LS devices. Its VIH/VIL thresholds and output drive levels ensure seamless integration into existing TTL-based designs without redesign.
Does SN74ALS157AN support three-state outputs?
No, SN74ALS157AN does not provide three-state outputs. Its outputs are active-high, push-pull, and non-inverting. When the strobe input (G) is high, all outputs enter a high-impedance state - but this is achieved via internal disable logic, not a dedicated output-enable pin. This differs from true 3-state devices like the 74ALS257.
What is the maximum clock rate supported by SN74ALS157AN in a synchronous design?
SN74ALS157AN has a maximum propagation delay of 14 ns (G→Y) and 14 ns (A/B→Y) under worst-case conditions. In practice, it supports reliable operation in synchronous systems with clock periods ≥ 28 ns - corresponding to a maximum toggle rate of ~35 MHz. For guaranteed timing closure, derate by 20% and verify with actual load capacitance and supply conditions.
Can SN74ALS157AN be used with 3.3 V logic systems?
No, SN74ALS157AN is not 3.3 V compatible. It requires a nominal 5 V supply (4.5–5.5 V range) and has TTL input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V). Direct interfacing with 3.3 V CMOS outputs may result in marginal or invalid logic levels; level-shifting circuitry or a 74LVC-series multiplexer is required for mixed-voltage systems.
Is SN74ALS157AN still in active production, and what is its RoHS status?
Yes, SN74ALS157AN is an actively produced part per Texas Instruments' packaging addendum, with PDIP (N) package, 25-unit tube packaging, and RoHS-compliant NiPdAu lead finish. It carries "Active" status and is designated for commercial temperature range (0°C to 70°C), with full traceability and lifecycle support available through authorized distributors.
SN74ALS157AN 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:
- 400µA, 8mA
- 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
SN74ALS157AN FAQ
1.How can I place an order for SN74ALS157AN through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS157AN 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 SN74ALS157AN reliable?
The price and inventory of SN74ALS157AN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS157AN is usually 5 days.
3.What payment methods are accepted for SN74ALS157AN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS157AN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS157AN?
SN74ALS157AN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS157AN 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 SN74ALS157AN?
For technical support, including SN74ALS157AN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS157AN requirements.
6.How does Aetrix verify that SN74ALS157AN is sourced from the original manufacturer or authorized distributors?
All SN74ALS157AN 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 SN74ALS157AN meets industry standards.
7.What is the process for return or replacement of SN74ALS157AN?
All SN74ALS157AN units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS157AN, 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 SN74ALS157AN part is unused and in its original packaging.
Return procedure for SN74ALS157AN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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