Texas Instruments SN74ALS151DR

Overview

SN74ALS151DR from Texas Instruments is a TTL-compatible 8-line to 1-line data multiplexer with active-low enable (G), complementary outputs (Y and W), and binary-select inputs (A, B, C). It operates from 4.5 V to 5.5 V at 0°C to 70°C, delivers 24 mA low-level output drive, and supports propagation delays as low as 3 ns (D→Y). It serves as a data source selector in digital control logic, address decoding, and Boolean function generation.

For engineers reviewing the SN74ALS151DR datasheet, SN74ALS151DR pinout, SN74ALS151DR application, or SN74ALS151DR equivalent, key selection criteria include its 16-pin SOIC (D) package, dual-output architecture (Y/W), ALS-family speed-power tradeoff, and compatibility with legacy 74-series TTL logic families in industrial control and instrumentation systems.

Technical Context

The SN74ALS151DR implements full binary decoding of three select lines (A, B, C) to route one of eight data inputs (D0–D7) to the true output (Y) while simultaneously driving the complemented output (W). Its strobe (G) input enables or disables both outputs: G = high forces Y = low and W = high, independent of select or data states.

Designed using Advanced Low-Power Schottky (ALS) bipolar technology, it achieves lower power consumption than standard LS TTL while maintaining compatible voltage thresholds (VIH = 2.0 V min, VIL = 0.8 V max) and higher drive strength (IOL = 24 mA) than 74LS151. It is not a 3-state device - outputs are always active (totem-pole), with no high-impedance mode.

Key Specifications

Pinout & Package

SN74ALS151DR uses a 16-pin SOIC (D) package per TI's package drawing D016A, with 1.27 mm pitch, 10.4 mm × 7.4 mm body, and 2.00 mm max height. Pin 1 is located at the top-left corner (quadrant Q1) per tape-and-reel orientation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8:1 multiplexer applications.

Compared with SN74LS151N, SN74ALS151DR reduces power by ~40% at equal speed; compared with SN74AS151NSR, it trades 2× speed for 60% lower ICC and better noise margin - making it optimal for mid-speed industrial control where thermal and supply constraints matter.

Availability

SN74ALS151DR is available at Aetrix Electronics and suitable for industrial control logic, microprocessor address decoding, parallel-to-serial conversion, and digital test equipment signal routing requiring stable component supply and long-term obsolescence management.

Supply support for SN74ALS151DR 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 consumer reach.

The SN74ALS151DR belongs to TI's legacy 74ALS logic family, engineered for reliable, medium-speed digital interfacing in commercial-temperature environments where power efficiency and TTL compatibility are critical.

FAQ

What is the maximum clock frequency supported by SN74ALS151DR in a synchronous multiplexing application?

The SN74ALS151DR does not operate on a clock signal - it is combinatorial logic. Its usable data rate depends on propagation delay and system timing margins. With a maximum tPHL/tPLH of 18 ns (Y output) and 24 ns (W output), it supports reliable operation in synchronous systems up to approximately 33 MHz (1/18 ns ≈ 55 MHz theoretical, but derated for setup/hold and skew). The SN74ALS151DR is typically deployed in address decoding and control logic below 20 MHz.

Does SN74ALS151DR support 3-state (high-impedance) outputs?

No, SN74ALS151DR does not feature 3-state outputs. It provides two active-drive outputs: Y (true) and W (complement), both always driven to valid logic levels. When the strobe (G) input is high, Y is forced low and W is forced high - neither enters high-impedance. For bus-sharing applications requiring tri-state capability, consider alternatives like SN74ALS251 or SN74LS251.

Can SN74ALS151DR be used with 3.3 V logic systems?

SN74ALS151DR is specified only for 4.5 V to 5.5 V operation and is not 3.3 V tolerant. Its input thresholds (VIH = 2.0 V min, VIL = 0.8 V max) may accept 3.3 V logic HIGHs, but VCC must be 5 V. Driving its inputs from 3.3 V CMOS sources risks marginal noise immunity and violates recommended operating conditions. Use level translators or a 3.3 V–compatible multiplexer (e.g., SN74LVC151A) for native 3.3 V systems.

What is the purpose of the W output on SN74ALS151DR?

The W output on SN74ALS151DR is the logical complement of the Y output - when Y = HIGH, W = LOW, and vice versa - except when the strobe (G) is high, in which case Y = LOW and W = HIGH regardless of select or data inputs. This eliminates the need for an external inverter in applications requiring both polarities, such as differential bus drivers or dual-edge-triggered logic. The SN74ALS151DR's W output is fully buffered and rated for the same 24 mA sink current as Y.

Is SN74ALS151DR pin-compatible with SN74LS151?

Yes, SN74ALS151DR is pin-compatible and functionally equivalent to SN74LS151 in SOIC (D) and PDIP (N) packages. Both share identical pin assignments, truth table behavior, and electrical interface characteristics (VIH/VIL, VOH/VOL). The SN74ALS151DR offers improved speed (15 ns vs. 22 ns max delay) and lower power (12 mA ICC vs. 19 mA), making it a direct performance upgrade with no PCB changes required.