Texas Instruments SN74ALS151DB

Overview

SN74ALS151DB from Texas Instruments is an 8-line to 1-line TTL-compatible data selector/multiplexer with active-low enable (G), three binary select inputs (A, B, C), and complementary outputs (Y and W). It operates over 0°C to 70°C, supports 5 V ±10% supply, delivers 24 mA low-level output drive, and exhibits propagation delays as low as 3 ns (D→Y) under 50 pF load - used in digital logic routing, function generation, and parallel-to-serial conversion in industrial control and legacy computing systems.

For engineers reviewing the SN74ALS151DB datasheet, SN74ALS151DB pinout, SN74ALS151DB application, or SN74ALS151DB equivalent, key selection criteria include its ALS family speed-power trade-off, dual-output complementarity, input clamping diodes for system-level ESD robustness, and compatibility with standard 16-pin SOIC (D) footprint layouts.

Technical Context

The SN74ALS151DB 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 when strobe G is low; W provides the inverted output. Its internal architecture uses bipolar ALS (Advanced Low-Power Schottky) transistor logic, delivering faster switching than standard LS while maintaining lower power consumption than AS variants.

Input clamping diodes are integrated on all data and select inputs, enabling direct connection to unbuffered CMOS or open-collector sources without external protection. The device features totem-pole outputs with guaranteed VOH ≥2.4 V at IOH = −2.6 mA and VOL ≤0.4 V at IOL = 24 mA, ensuring noise margin compliance in mixed-logic systems.

Key Specifications

Pinout & Package

SN74ALS151DB is supplied in a 16-pin SOIC (Small-Outline Integrated Circuit) package, 3.9 mm body width, 1.75 mm height, 1.27 mm lead pitch, RoHS-compliant NiPdAu finish, MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-line to 1-line multiplexer applications.

Compared with SN74LS151N, SN74ALS151DB offers 47% faster switching and integrated clamps at modest power cost; versus SN74AS151NSR, it trades 15 ns speed for 60% lower ICC and superior noise immunity - making it optimal for balanced industrial control designs.

Availability

SN74ALS151DB is available at Aetrix Electronics and suitable for industrial control panels, legacy computer upgrades, and test equipment requiring stable component supply with long-term lifecycle support.

Supply support for SN74ALS151DB 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 for industrial, automotive, and communications markets.

The SN74ALS151DB belongs to TI's legacy TTL logic portfolio, designed specifically for reliability-critical upgrades of 1980s-era digital systems where ALS speed-power balance and input ruggedness are essential.

FAQ

What is the maximum operating frequency supported by the SN74ALS151DB?

The SN74ALS151DB does not specify a maximum clock frequency, but its propagation delays (3–18 ns) support reliable operation in systems with data/address bus cycles down to 40 ns (25 MHz). For clean 8:1 selection, ensure setup/hold times of ≥5 ns are met at the A/B/C and G inputs relative to data edges. The SN74ALS151DB is optimized for synchronous control in microprocessor peripheral interfacing rather than continuous high-frequency streaming.

Can the SN74ALS151DB interface directly with 3.3 V logic devices?

Yes, the SN74ALS151DB accepts 3.3 V logic levels on its inputs: VIH(min) = 2.0 V and VIL(max) = 0.8 V are comfortably exceeded by 3.3 V CMOS outputs. However, its outputs swing 0–5 V, so level-shifting is required if driving 3.3 V inputs. The SN74ALS151DB's input clamping diodes also protect against minor overshoot when interfacing with unbuffered 3.3 V sources.

Does the SN74ALS151DB have power-on reset behavior or metastability immunity?

No, the SN74ALS151DB is a purely combinatorial device with no internal state or reset function. During power-up, outputs enter indeterminate states until VCC stabilizes and valid inputs are applied. Metastability is not applicable since it lacks clocked elements; however, asynchronous changes on A/B/C/G while data is transitioning may cause momentary glitches on Y/W - proper synchronous control or external filtering is recommended in critical paths.

What is the purpose of the W output on the SN74ALS151DB?

The W output on the SN74ALS151DB is the logical inverse of the Y output - when Y = HIGH, W = LOW, and vice versa. This complementary pair enables direct implementation of logic functions like XOR, XNOR, or active-low enable gating without adding external inverters. In the SN74ALS151DB, W is fully buffered and specified for the same 24 mA sink capability as Y, ensuring matched timing and drive strength.

Is the SN74ALS151DB pin-compatible with the SN74LS151 and SN74AS151 families?

Yes, the SN74ALS151DB shares identical pinout, terminal functions, and 16-pin SOIC (D) package dimensions with SN74LS151 and SN74AS151 variants. All three support the same D0–D7, A–C, G, Y, W, VCC, and GND connections. However, electrical differences - including propagation delay, drive strength, and input thresholds - require validation in the target application before substitution.