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Texas Instruments SN74AS157DR
- Part No.:
- SN74AS157DR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74AS157DR.pdf
- Description:
- IC MULTIPLEXER 4 X 2:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,301
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Product details
Overview
SN74AS157DR from Texas Instruments is a quad 2-line-to-1-line data selector/multiplexer with true (non-inverting) output logic, buffered inputs/outputs, and TTL-compatible voltage thresholds. It operates from 4.5 V to 5.5 V at 0°C to 70°C, delivers 20 mA sink current, and achieves propagation delays as low as 1 ns (tPHL from A/B to Y). It routes one of two 4-bit data sources to four outputs under control of a common select line (A/B) and strobe (G), used in bus management and digital signal routing.
For engineers reviewing the SN74AS157DR datasheet, SN74AS157DR pinout, SN74AS157DR application, or SN74AS157DR equivalent, key selection criteria include its 16-pin SOIC-D package, 20 mA output drive capability, sub-11 ns max propagation delay across all input-to-output paths, and compatibility with standard TTL logic families in industrial control and legacy computing systems.
Technical Context
The SN74AS157DR implements four independent 2:1 multiplexers sharing a single A/B select input and a global enable (strobe G) input. Each channel selects between corresponding A and B inputs (1A/1B, 2A/2B, 3A/3B, 4A/4B) and drives true (non-inverted) outputs (1Y–4Y).
Its AS-series bipolar TTL architecture provides higher speed and stronger drive than ALS variants: typical tPLH/tPHL from A/B to Y is 2 ns/2 ns, and from G to Y is 2 ns/2 ns (VCC = 4.5–5.5 V, CL = 50 pF), with ICC = 17.5–28 mA at VCC = 5.5 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Quad 2-line-to-1-line data selector/multiplexer with true (non-inverting) outputs |
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5 V TTL power rails |
| Output Drive | 20 mA sink (IOL), −2 mA source (IOH) - sufficient to drive multiple TTL inputs or small capacitive loads |
| Propagation Delay | Max 6 ns (A/B → Y), 7.5 ns (G → Y) - enables high-speed bus arbitration in real-time control |
| Operating Temperature | 0°C to 70°C - rated for commercial/industrial ambient environments |
| Input Thresholds | VIL = 0.8 V, VIH = 2.0 V - ensures robust noise margin against TTL-level signals |
| Package | 16-pin SOIC (D), 7.5 mm × 10.3 mm body, RoHS-compliant NiPdAu lead finish |
Pinout & Package
SN74AS157DR is housed in a 16-pin small-outline integrated circuit (SOIC-D) package with 1.27 mm pitch, 7.5 mm width, and 10.3 mm length. Pin 1 is marked by a beveled corner or notch; the device uses standard DIP-compatible footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A, 2A, 3A, 4A | Data Input A side | Four independent inputs selecting source A for each multiplexer channel |
| 1B, 2B, 3B, 4B | Data Input B side | Four independent inputs selecting source B for each multiplexer channel |
| 1Y, 2Y, 3Y, 4Y | True Output | Non-inverted outputs - directly reflect selected A or B input per channel |
| A/B | Select Control | Global 2:1 select line: LOW = route A inputs, HIGH = route B inputs |
| G | Strobe / Enable | Active-LOW enable: LOW = outputs enabled, HIGH = outputs forced LOW (not high-Z) |
| VCC | Power Supply | Positive supply terminal (4.5–5.5 V); must be decoupled locally |
| GND | Ground Reference | Return path for all I/O and supply currents; requires low-impedance connection |
Key Features
| Feature | Design Value |
|---|---|
| True (non-inverting) output logic | Eliminates need for external inverters in signal routing paths, reducing component count and propagation delay |
| 20 mA output sink capability | Drives up to 10 standard TTL loads or interfaces directly with medium-current peripherals without buffers |
| Sub-11 ns max propagation delay | Supports >50 MHz bus switching rates in synchronous digital systems with tight timing budgets |
| Buffered inputs and outputs | Reduces loading on upstream drivers and improves noise immunity across PCB traces |
| TTL-compatible input thresholds | Ensures interoperability with legacy 74LS, 74ALS, and microcontroller GPIO without level-shifting |
Applications
| Industrial PLC I/O Expansion | Legacy Computer Bus Arbitration |
|---|---|
Use Scenario: Expanding discrete input channels in programmable logic controllers by multiplexing sensor signals onto shared data lines. IC Role / Device Role / Timing Role: Data selector routing up to eight digital sensor inputs (four A/B pairs) into four processor-read channels under firmware-controlled A/B and G signals. Use Value: Reduces microcontroller GPIO usage by 50% while maintaining deterministic 6 ns worst-case latency for real-time response. | Use Scenario: Managing shared address/data bus access between CPU, DMA controller, and peripheral ICs in 1980s–1990s embedded systems. IC Role / Device Role / Timing Role: Quad 2:1 mux resolving contention by selecting active bus master based on priority-encoded A/B and strobe G control. Use Value: Enables cycle-accurate bus handoff with <11 ns delay, preserving original system timing margins without redesign. |
| Test Equipment Signal Routing | Digital Audio Switching Matrix |
Use Scenario: Configurable signal path selection in automated test equipment for routing DUT outputs to measurement instruments. IC Role / Device Role / Timing Role: Four independent 2:1 switches controlled by FPGA I/O, enabling dynamic reconfiguration of analog/digital signal chains. Use Value: Provides deterministic, glitch-free switching with TTL-compatible control and 20 mA drive for driving instrument input stages. | Use Scenario: Channel-select logic in vintage digital audio gear (e.g., CD players, DAC switchers) routing stereo left/right data streams. IC Role / Device Role / Timing Role: Selecting between two PCM data sources (e.g., CD vs. DAT) for 4-bit-wide parallel audio word transfer. Use Value: Maintains bit-accurate timing with <7 ns G-to-Y delay, preventing sample misalignment in time-critical audio paths. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar quad 2:1 multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS157ADR | Slower (max 14 ns A/B→Y), lower ICC (6–11 mA), same pinout and logic function | Better suited for low-power, noise-sensitive applications where speed <20 MHz is acceptable | Choose when thermal budget or static power is critical and 14 ns delay is acceptable |
| SN74HC157DR | CMOS technology, 2–6 V supply, 7.5 mA IOL, higher noise immunity, no TTL DC compatibility | Requires level translation for legacy 5 V TTL systems; preferred in mixed-voltage or battery-powered designs | Choose for modern low-voltage systems or when integrating with HC-series logic; avoid in pure TTL backplanes |
Compared with SN74ALS157ADR and SN74HC157DR, the SN74AS157DR delivers the highest speed and strongest drive in a drop-in SOIC package but consumes more quiescent current - optimal for performance-critical 5 V TTL systems where timing closure is constrained.
Availability
SN74AS157DR is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy computer bus arbitration, and test equipment signal routing requiring stable component supply and long-term obsolescence support.
Supply support for SN74AS157DR 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, embedded processing, and logic ICs for industrial, automotive, and communications markets.
The SN74AS157DR belongs to TI's 74AS advanced Schottky TTL logic family, designed for high-speed digital systems requiring fast propagation, strong drive, and direct compatibility with legacy 5 V TTL infrastructure.
FAQ
What is the maximum operating temperature range for the SN74AS157DR?
The SN74AS157DR is characterized for operation from 0°C to 70°C, matching the commercial temperature grade. It is not rated for extended industrial (−40°C to +85°C) or military (−55°C to +125°C) ranges. Operation outside 0°C–70°C may result in parametric shift or functional failure, and is not supported by TI's datasheet specifications for SN74AS157DR.
Does the SN74AS157DR have three-state outputs?
No, the SN74AS157DR does not feature three-state outputs. When the strobe input G is HIGH, all outputs (1Y–4Y) are forced LOW - not high-impedance. This differs from 3-state multiplexers like the SN74LS251. The SN74AS157DR uses active-LOW enable with true-level outputs only, requiring external isolation if bus-sharing is needed.
What is the recommended decoupling for SN74AS157DR?
TI recommends a 0.1 µF ceramic capacitor placed as close as possible to the VCC and GND pins of the SN74AS157DR, with short, low-inductance traces. For boards with multiple SN74AS157DR devices or high switching activity, add a bulk 4.7 µF–10 µF tantalum or aluminum electrolytic capacitor near the power entry point to suppress low-frequency ripple and supply sag.
Can SN74AS157DR be used as a level shifter between 3.3 V and 5 V logic?
No, the SN74AS157DR is not a level shifter. Its inputs require TTL-compatible thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V) and it operates only from 4.5–5.5 V. Driving it with 3.3 V logic may cause unreliable switching due to marginal VIH margin. For 3.3 V → 5 V translation, use dedicated level shifters such as TXB0104 or SN74AVC4T245 instead of SN74AS157DR.
Is SN74AS157DR pin-compatible with SN74LS157N?
Yes, SN74AS157DR is pin-compatible with SN74LS157N and other 16-pin variants (e.g., SN74ALS157ADR, SN74HC157DR) in the same SOIC-D or PDIP-16 packages. All share identical pin assignments for inputs (1A–4B, A/B, G), outputs (1Y–4Y), and power (VCC, GND). However, electrical behavior (speed, drive, current) differs significantly - verify timing and loading in final design.
SN74AS157DR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74AS157DR FAQ
1.How can I place an order for SN74AS157DR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AS157DR 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 SN74AS157DR reliable?
The price and inventory of SN74AS157DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AS157DR is usually 5 days.
3.What payment methods are accepted for SN74AS157DR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AS157DR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AS157DR?
SN74AS157DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AS157DR 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 SN74AS157DR?
For technical support, including SN74AS157DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AS157DR requirements.
6.How does Aetrix verify that SN74AS157DR is sourced from the original manufacturer or authorized distributors?
All SN74AS157DR 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 SN74AS157DR meets industry standards.
7.What is the process for return or replacement of SN74AS157DR?
All SN74AS157DR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AS157DR, 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 SN74AS157DR part is unused and in its original packaging.
Return procedure for SN74AS157DR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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