Texas Instruments SN74ALS151D

Overview

SN74ALS151D from Texas Instruments is an 8-line to 1-line TTL-compatible data selector/multiplexer in a 16-pin SOIC package, operating from 0°C to 70°C with 5 V supply, 24 mA low-level output drive, and propagation delays as low as 3 ns (tPLH, D→Y). It performs Boolean function generation and parallel-to-serial conversion in digital logic systems.

For engineers reviewing the SN74ALS151D datasheet, SN74ALS151D pinout, SN74ALS151D application, or SN74ALS151D equivalent, key selection criteria include its dual complementary outputs (Y and W), active-low strobe enable (G), binary-select inputs (A/B/C), and compatibility with standard TTL logic families in legacy control and data routing circuits.

Technical Context

The SN74ALS151D implements full binary decoding across three select lines (A, B, C) to route one of eight data inputs (D0–D7) to the true output (Y) while simultaneously driving the inverted output (W). Its strobe input (G) must be low to enable selection; when high, Y is forced low and W high - enabling cascading and gating functions.

Designed for standard TTL voltage thresholds, it features input clamping diodes, 0.4 V typical VIL, 2 V VIH, and guaranteed 2.4 V VOH at −2.6 mA and 0.4 V VOL at 24 mA - ensuring robust noise margin and interoperation with 74LS/74S logic without level-shifting.

Key Specifications

Pinout & Package

SN74ALS151D uses a 16-pin plastic small-outline integrated circuit (SOIC) package per TI's D drawing, with 1.27 mm pitch, 7.5 mm body width, and 10.3 mm length. Pin 1 is marked by a beveled corner or notch on the top surface.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74LS151N and SN74AS151N, the SN74ALS151D delivers balanced performance: 3× the speed of LS with only 1.6× the power, and 2× the drive of LS without AS-level noise sensitivity - making it optimal for mid-speed industrial control where reliability and compatibility are prioritized.

Availability

SN74ALS151D is available at Aetrix Electronics and suitable for industrial control panels, test instrumentation, legacy system upgrades, and educational logic labs requiring stable component supply and long-term obsolescence management.

Supply support for SN74ALS151D 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 solutions with broad industrial, automotive, and aerospace reach.

The SN74ALS151D belongs to TI's 74ALS advanced low-power Schottky logic family, engineered for improved speed-power trade-offs in TTL-based digital systems while maintaining pin and functional compatibility with earlier 74LS and 74S series.

FAQ

What is the maximum clock rate supported by SN74ALS151D in a data selection application?

The SN74ALS151D does not operate on a clock signal - it is a purely combinational device. Its usable data rate depends on propagation delay and system setup/hold timing. With tPHL/tPLH as low as 3–8 ns (D→Y), it supports reliable selection cycles up to approximately 100 MHz in minimal-load configurations. For SN74ALS151D, ensure input signals are stable ≥3 ns before and after the effective selection edge to avoid glitches.

Does SN74ALS151D support 3.3 V logic interfaces?

No, SN74ALS151D is a 5 V-only TTL device with absolute maximum VCC of 7 V and recommended operation at 4.5–5.5 V. Its input thresholds (VIH = 2 V min, VIL = 0.8 V max) and output levels (VOH ≈ 3.2 V at −2.6 mA) are incompatible with 3.3 V CMOS logic without level translation. Direct connection to 3.3 V systems may cause unreliable operation or excessive current draw.

Can SN74ALS151D be used to generate a 3-input XOR function?

Yes, SN74ALS151D can implement any 3-input combinational logic function, including XOR, by wiring D0–D7 to match the truth table: D0=0, D1=1, D2=1, D3=0, D4=1, D5=0, D6=0, D7=1. With A, B, C as inputs, Y produces the 3-input XOR result. The SN74ALS151D's complementary W output is not needed for XOR but may assist in related logic reduction.

Is SN74ALS151D pin-compatible with SN74LS151?

Yes, SN74ALS151D is fully pin-compatible and functionally equivalent to SN74LS151 in SOIC (D), PDIP (N), and SOP (NS) packages. Both share identical pin assignments, logic behavior, and truth table. The SN74ALS151D offers improved speed (≈2× faster), lower power (≈30% less ICC), and higher output drive (24 mA vs 8 mA), making it a direct performance upgrade.

What is the purpose of the W output on SN74ALS151D?

W is the inverted complement of the Y output - when Y = HIGH, W = LOW, and vice versa. This eliminates the need for an external inverter in applications requiring both true and complemented versions of the selected data, such as implementing sum-of-products logic, differential bus driving, or dual-edge triggered control signals. For SN74ALS151D, W is electrically identical to Y except for polarity, with matching timing specs.