Texas Instruments SN74ALS157ADR

Overview

SN74ALS157ADR from Texas Instruments is a quad 2-line-to-1-line data selector/multiplexer in a 16-pin SOIC package, delivering true (non-inverted) output logic with buffered inputs and outputs. It operates across 0°C to 70°C, supports 4.5 V–5.5 V supply, and routes one of two 4-bit input sources to four outputs under control of a common strobe (G) and select (A/B) inputs - used in address/data bus switching and digital logic state routing.

For engineers reviewing the SN74ALS157ADR datasheet, SN74ALS157ADR pinout, SN74ALS157ADR application, or SN74ALS157ADR equivalent, key selection criteria include propagation delay (tPLH/tPHL ≤ 14 ns max at VCC = 4.5 V), output drive capability (IOL = 4 mA min), TTL-compatible input thresholds, and SOIC-D package compatibility with automated SMT assembly.

Technical Context

The SN74ALS157ADR implements four independent 2:1 multiplexers sharing a single A/B select line and global enable (G) input. Each channel selects between corresponding A and B inputs (e.g., 1A/1B → 1Y) and drives true-level outputs without inversion. Its ALS (Advanced Low-Power Schottky) logic family delivers lower power than standard LS while maintaining compatible voltage thresholds and drive strength.

Internal architecture includes input buffers, gating logic for A/B selection and G-enable control, and totem-pole output stages. No 3-state or open-collector functionality is present - all outputs are actively driven high or low. Timing behavior is characterized with CL = 50 pF and RL = 500 Ω loads per JEDEC standards.

Key Specifications

Pinout & Package

SN74ALS157ADR uses a 16-pin SOIC (D) package per TI drawing D0016A, with 1.27 mm pitch, 7.5 mm body width, and 2.00 mm max height. Pin 1 is located at top-left corner with beveled edge marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ALS157AN, SN74ALS157ADR provides identical logic and electrical behavior in a surface-mount package optimized for automated manufacturing; versus SN74AS157DR, it trades 2× lower speed for 2.5× lower quiescent current - making it preferable for thermally constrained or battery-backed systems.

Availability

SN74ALS157ADR is available at Aetrix Electronics and suitable for bus arbitration, address selection, data path switching, and test mode logic requiring stable component supply and long-term industrial availability.

Supply support for SN74ALS157ADR 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 with broad industrial, automotive, and communications portfolio coverage.

The SN74ALS157ADR belongs to TI's legacy 74ALS logic family, designed for reliable, low-power, TTL-compatible digital interfacing in commercial-grade embedded systems and retro-computing upgrades.

FAQ

What logic family does the SN74ALS157ADR belong to, and how does it differ from standard 74LS?

The SN74ALS157ADR belongs to the Advanced Low-Power Schottky (74ALS) logic family. Compared to standard 74LS, it achieves approximately 30% lower quiescent current (ICC ≤ 11 mA vs. ~20 mA for LS) while maintaining compatible input thresholds and output drive. Its propagation delay is slightly faster than LS but slower than AS, striking a balance between speed and power for commercial applications. The SN74ALS157ADR retains full pin and functional compatibility with other 74ALS and 74LS 157 variants.

Does the SN74ALS157ADR support 3-state outputs?

No, the SN74ALS157ADR does not support 3-state (high-impedance) outputs. All four Y outputs are actively driven high or low based on the selected input and enable condition. When G = HIGH, outputs are forced HIGH regardless of A/B or data inputs - this is a hard-wired active-HIGH disable, not a high-impedance state. For true 3-state operation, consider alternatives like SN74ALS257 or SN74ALS158 with explicit output-enable controls.

What is the maximum clock/data rate supported by the SN74ALS157ADR in a synchronous design?

The SN74ALS157ADR is not a clocked device but a combinational multiplexer. Its usable data rate depends on propagation delay and load. With tPLH/tPHL ≤ 14 ns (max, VCC = 4.5 V) and CL = 50 pF, it supports reliable operation in systems with clock periods ≥ 30 ns - effectively supporting synchronous logic up to ~33 MHz. For higher rates, derating for temperature, supply variation, and board trace capacitance is required; SN74AS157DR would be preferred above 40 MHz.

Can the SN74ALS157ADR be used with 3.3 V logic systems?

No, the SN74ALS157ADR is not 3.3 V compatible. It requires VCC = 4.5 V to 5.5 V and has TTL-level input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V). While a 3.3 V signal may register as HIGH in some cases, it violates the guaranteed VIH spec and risks unreliable operation due to insufficient noise margin. Interfacing with 3.3 V systems requires level-shifting circuitry or selection of a 3.3 V–tolerant logic family such as 74LVC or 74AHC.

How is the SN74ALS157ADR pinout validated for the SOIC-D package?

The SN74ALS157ADR pinout is validated per Texas Instruments' official datasheet SDAS081C (Rev. December 1994), Figure "SN74ALS157A, SN74ALS158, SN74AS157, SN74AS158 . . . D OR N PACKAGE (TOP VIEW)", which explicitly maps pins 1–16 for the D package. Pin 1 (1A) is at top-left; GND is pin 8; VCC is pin 16; and outputs 1Y–4Y occupy pins 4, 7, 9, and 12. This layout matches TI's SOIC-D mechanical drawing D0016A and is confirmed in TI's Package Option Addendum for SN74ALS157ADR.