Texas Instruments SN74AS157DRG4

Overview

SN74AS157DRG4 from Texas Instruments is a quad 2-line-to-1-line data selector/multiplexer with true (non-inverting) output logic, designed for high-speed digital signal routing in TTL-compatible systems. It features 16-pin SOIC (D) package, operates from 4.5 V to 5.5 V, delivers 20 mA sink current, and achieves propagation delays as low as 1 ns (tPHL from A/B to Y) at VCC = 5 V, CL = 50 pF - ideal for address/data bus selection in industrial control and legacy computing interfaces.

For engineers reviewing the SN74AS157DRG4 datasheet, SN74AS157DRG4 pinout, SN74AS157DRG4 application, or SN74AS157DRG4 equivalent, key selection considerations include its AS-series speed grade, true-output logic polarity, 0°C to 70°C commercial temperature range, buffered I/O architecture, and compatibility with standard 5-V TTL logic families in multiplexed data path designs.

Technical Context

The SN74AS157DRG4 implements four independent 2:1 multiplexers sharing a common select (A/B) and strobe (G) input. Each channel routes either input A or B to its corresponding Y output based on the A/B state, with G enabling/disabling all outputs simultaneously. All inputs and outputs are fully buffered, eliminating fanout limitations typical of unbuffered logic.

It belongs to the 74AS family - Advanced Schottky TTL - optimized for speed-power trade-offs over standard 74LS/ALS, achieving sub-10 ns propagation delays while maintaining TTL voltage thresholds (VIH = 2.0 V, VIL = 0.8 V) and drive capability (IOL = 20 mA). No internal 3-state logic or latch functionality is present.

Key Specifications

Pinout & Package

SN74AS157DRG4 is supplied in a 16-pin SOIC (D) package per JEDEC MS-012, 7.5 mm body width, 1.75 mm height max, with 1.27 mm pitch. Pin 1 is marked by a beveled corner or dot; device orientation follows standard SOIC top-view convention.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad 2:1 multiplexer applications.

Compared with SN74ALS157ADR and SN74HC157DR, SN74AS157DRG4 uniquely balances 5-V TTL compatibility, sub-11 ns speed, and 20 mA drive in a surface-mount SOIC package - making it the optimal choice for timing-critical industrial control and legacy computing upgrades where signal integrity and fanout matter.

Availability

SN74AS157DRG4 is available at Aetrix Electronics and suitable for industrial control systems, test equipment signal routing, and legacy microprocessor bus expansion requiring stable component supply, long-lifecycle support, and verified 5-V TTL interoperability.

Supply support for SN74AS157DRG4 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 over 50 years of innovation in high-reliability digital ICs.

The SN74AS157DRG4 belongs to TI's 74AS Advanced Schottky TTL logic family, engineered for high-speed, low-noise data routing in industrial, test, and computing applications where TTL compatibility and timing precision are essential.

FAQ

What logic family does SN74AS157DRG4 belong to, and how does it differ from 74LS or 74HC variants?

SN74AS157DRG4 is part of the 74AS (Advanced Schottky) TTL family. It offers significantly faster propagation delays (≤11 ns) than 74LS (≤25 ns) and higher drive strength (20 mA sink) than 74HC (4 mA), while maintaining TTL-compatible voltage thresholds. Unlike CMOS-based 74HC, SN74AS157DRG4 requires a regulated 5-V supply and draws higher quiescent current (28 mA), but delivers superior noise-immune performance in electrically harsh environments.

Does SN74AS157DRG4 support 3-state outputs, and what happens when the G (strobe) input is HIGH?

No, SN74AS157DRG4 does not feature 3-state outputs. When G is HIGH, all Y outputs are forced LOW regardless of A/B or data inputs - this is a hard-wired disable, not high-impedance. To achieve bus isolation, external tri-state buffers or a different multiplexer (e.g., SN74AS257) would be required. The G input functions strictly as an active-HIGH enable/disable, not an output control.

What is the maximum clock rate or data rate supported by SN74AS157DRG4 in a synchronous bus application?

SN74AS157DRG4 is not a clocked device and has no internal clock. Its usable data rate depends on propagation delay and system timing margins. With a worst-case tPHL/tPLH of 11 ns and setup/hold times <2 ns, it supports reliable operation in bus systems up to ~25 MHz (40 ns period), assuming clean edges and proper termination. For higher rates, verify timing closure with actual board trace lengths and load capacitance.

Can SN74AS157DRG4 be used with 3.3-V logic systems?

SN74AS157DRG4 is specified only for 4.5–5.5 V operation and is not 3.3-V tolerant. Driving its inputs from 3.3-V sources risks violating the VIH minimum (2.0 V) under worst-case conditions and may cause unreliable switching. Interfacing with 3.3-V systems requires level translation (e.g., TXB0104) or substitution with a 3.3-V–compatible multiplexer like SN74LVC157A.

What package type and RoHS status does SN74AS157DRG4 have, and is lead-free soldering supported?

SN74AS157DRG4 uses a 16-pin SOIC (D) package with NiPdAu (NIPDAU) lead finish and is RoHS compliant. It carries a JEDEC MSL Level-1 rating with unlimited floor life and peak reflow tolerance up to 260°C - fully compatible with standard lead-free soldering profiles per IPC-J-STD-020. The "G4" suffix confirms green (halogen-free) and RoHS-compliant construction.